. .. . . . 2 .2 _ . . 2‘. 2.121.002.2120. .... ...... 2.. I. 2102..2v ...0...xu.muw2,2..f$. 2F.» .1.2.).00.0..0.‘.2.“..02222..:. 22.. . u... .22 2 d 0. I. 0.0.... 2 ‘II 0 .10 a: Qffi 2.0000 2209:2022420 00—00002’02K 2 . .0 0 2.0 0 000.0”0OJMJ120 200022000... 2 1‘ 3.0245 2 s 00 .220 :2 . 2 0.22.. 22 2 ..0 u... . .220 ...22 2. 02000. . MD 2 2 m .3...) “020 2.“.“L 00' 000.“ 0 09:030.- 2100.04.02.01; 0’20... ~I 2‘... 200 . 00 200. 00 0.... .. ..V 0 . 2 02002020 0 $0.. 00 0,200.. 0’ 0. ”02“ 0 ‘22 ..00 2.10222... ...-02 ...22 r 2. 2. .2 .... 20 12.2.20 00. thin-“02.. 002.40. 1: *3.0 0. :ufinwm20400. 0.... . v.00 ... .22, 2 .2... "...... ...020 . 2. 0 2 f . .12.. . . o .... .2. n00 22 . 0 .2200 0 0 20.3.. ”A $00.03”? «rum... .200, J02 .J ., ..0. .020 . 220. 072 2 2 .0002 . 22. 2 2 0 .2222 J"...0.220‘2w0 . 2. . 1'00... 2.0,. .2. 2. . '00 . 2 0 . .W... 00. . "0». 0. ".02.. 02.. 0 2202...,232 2 .2! .0202! 20023 . 2.02.. 2 2.. 2 2. ..00. o2 00. ..0 00*2‘ 25000.“.430—2 .2030uhuu0”. 2 01.5%. .22”. ) E102. .2242 0 2.. .2-«2 20210.20... ..20222u: 20. 00.2 2.202.202.5212. 02 20.2.1.0 .0 002 0‘ . 3 0” .0»... ..2 ”c.2282... 10.232220222402202 28.2.22“. :00 . 0.00 0 020,120... '20:. 30. 2 0.1. 00 0.20 0 0. .0 2 .H00. 0 0 0 ‘0. 02022.: 95:2002?‘ 001qu29222"0.0 2 .. 0|. 0... 0 “000‘"220. . ...: 2—22. £202.03“... 2 022203.233. _ ....0 2.0.1.0. 02 . .. 0 2 u. ”2.2.0323. 2’. 0.n..00«00~2_..20200.0 1 ”Wh.82r0’i32!02«2 33.0.13 0032.000 00 .9003. 22- .00. 0 . 2 0 0 2 .2 0 00 p 2 .00. 0’2‘ 4" 00 2 22.022 2.02. 2020.00. 0 M5“: dmernflu..:022M.-u 2.2 2.3.0 32.0.01“ 3.0 20 20.2.. 02.2.2220 3| 2 .(3 411ké. 0002 0 0n. 2.? 2.0‘33 . 23¢. 2 2’0 90‘) 22020.0. 22.20 0022. 2.023: 002.0. 20%”222 12.2.3.0... . 220. 202.203.902.22 2020.02I3200... . . .. .200 J 'n .0 000300 0;) 00 ‘3‘. 0 0‘. V‘. I advoziuo...‘ 20.010 0.22. 0 v 0 0.0 v 2 0.0 O 002 .0 0000124.. 0 0 0.200 02020. 020.2 20.0". O 0 .0 . .r. 200’. '00 002.0. .. 7 2m. .0 2 2...”.O .2 I... I. 2.. .....2 2.020000 ’20.. 200.02.20’. .902 . 22.1.0 . 2 20. v .22 2-. .2. . 0 2 .20! .20 0220 .2 a. 0 o .02 .20. .0 .0 20.00 00020. 002..2.v 2 . ‘0. 2. .. (.20.. 50.02 . . 00 .. .2 0 0 .0002 22 2.2... . .0. 0 2. .20 .2 .2 .20 2.000. 0.2.. .v. . 0. .2 202 00.0. 002 . 0 2. 1.090.... . 2 . 222 0.20. 0.! . 00.2v)02.'o.0.l 000202.002. .2220. ”000‘ .2 .07 20-. 02“.Io:.0l.0.2 0‘ .2 300000220 22. 200.0. 2 2. 20. 100.0 00. 2'23 0.. . 3209000020 ..2 .. 3020. 02. .10.”. 2 0. 0: 2000.08 .2. v0.00. f.“-«V02022I00 {iv-.30 3027' . . 0 . 0 2. . 0 00. 2022031 2. 22.0.00: .2. 2 00......00 .202... . 1.00.020. 2 20:22.94 0.2. .202 09‘, 2 an“. I270 ‘20““035‘125 00.22 002‘ o 92. 02.2.2 0 . 0. 0. .2 OI 2 0 ‘22 2 20.0 . 02 . .020 20 2200020 2 0.0 .0. 0. 2 00 0.. 200.. c.0220. 420) .0 220’.- » , .02 (220.202.20.2- .. .202. 02. ..20.. .02 . 0.2202 any 2 “'0 2‘.- 2 , 3 . 2 In. .200. . 02‘! 02002020.. 2 0.00122. . 2.012.020 002. .0 220 0'2 000 0,22 ...-00“. . 2 . v . . 0 . . . 0 .02 ...-.5: ..4 222.0 ”3Y2” .. 022220 20 .2. I23 .00.22.3 00 ’22. 0.0.0 .201000 .2 . . 2 . .. ....l0.202_0202.220..‘..20. 20 2 .2 02 2 ..00 202000.- 0090000020.. 2. 2 2000.00.22 C00 2 0 0 . . . . .1000... . .3322»- v 0. . 2.0. 0 2 . . 2... 222.00 22 :00022. .0. 23.2202 0 0. .0 2.2210 20.00.. 2.2.22.2. 0.2.2 020, .2002200.IH4.2U..00 \O-fl.. .22. 220.0«0 000 .... . 0. .2 ... 22.... .2: 2.2, .0 0. .3212 25.... 0,2... I, .2. .2 2..“ . ... 2..., o ..20. 2. 0 . . ....20 050.032.] 202 002 I 0|0 .0000. ’00.“... .0 0 .4 . . 2 . . . . '00. ..0 I . . ...... 0.0. .0000 “02.0 2 2 _ _ . . . 0 .. . . 2 . . 0...02 00.202 2.010000 .004. n ‘0 2 o 0 02 .0 I 00... 0.. 0 .0020. .202 2 . .202 .0 I... 2. .3... 22.22.0220! 0002.22 200-..2Il020 . ’0‘. 2.00..0 2.0 0000290. .. 2 . 020.002.: 2 0.0 00. 9.. my . 20202220....0212 2.020 0.20020». 2.00. .. ..0 ... 5,29 .0 220.0 , 0 In: 0001-2200 0 2020000000020 2.12.0 ...-0.0!..03622000002. 2,2 v 2 0.1.0002... 0.3 . .00..J.20-. 2. 0 . 0’ I 20 0.2 000 00.0. may . .‘000 . ...-\0 24.2.0. .02. 2. 0022’? O 0 2 ....22 ..2 2 .. . 2... 2.. 2....228222JI3UN20 (2201220213200... .fi.3'o.20nl3023 0300 .0 .2 2 0 . 00 ...-0.0 .2 02 0.0. 0.20 0 ‘22 (202.23 2 2.002. 2 :0 03.0002. .00 0.02 2003.10.02. ....roi . .2 2 . .40.... . . . 1.2.020...‘I~2.22.2r2 2221) 22222230210; 222.212.22.222 200. pilligipi 2. _ 00......u 2. 0 0 .202. . .222 a 20. 02.320.020.220. .2252. 320222.32 02 2200.2’fa\302$0..122§3l(24( . .00 0 0 000 22 0 2 00. 0. .02 0 000.020. .. 2 . 0. .. 0.: 220.020. 2. .4. .1n2100002 . w . . O2 ‘ 1.222.}...20. 2 .022. (0.. .72.... 22.20022...)22)0l.2.222 22.3.1220}. .22. .22 .2220 2220. ,7. 22.2 2 .. 02 20.1003020122 22.2213522201202v32a2232 202; 050.302.25.23002flu22, 2 3223002.. . . ..I.. 002.1 020.22. 10.000 .002. 20220210305003.2320. 20.1 '5 0.2 0.2 0.0002 02. 2. . .222... . , . .. . 2 6300203022900.- 000.22.0003.23.1.202I70§:§£1’l2 2 02.0- .0 .20 0.220 .0 6 02.0 00. 20 . . . . .. . 2 . '3. O .000 00.000010200102000}; 01’ 333.5. 0 .2 .. . _ .0720 0.2200%«202.h22u 20020000373 10.200 2122,0513 .0 “2 . . 0! l0- l2 . 102,330.! ’22:: 0 .0“. 24.22.2020. .b 3 2.0. will; 2 35010.03!!1.0.)3\l0.\13209 W '..' ' 1*. .. 220.2. 2 02 .202. 242.822.... 200052.103. My 10w... ..02 0. 2.0% .322 20022005... . .2. a 2. 2.... '- .0 0. 0 2 ... . . . 2 2020: . 2’0r‘fur1hh0 222,00. 2.0.2.2120 00'2l2l..22.. 2. . .0 ‘1! 230.3 0 0 0 0 0 0. ”£0. 0 .0on00. 2 |.0‘0v2.0002 020022. 0 2&1”. \'02. . . 2'0. .0 l. 2. Cl 0 2. 00. 0-202 .2 002. ... 22 .225 ..0 o. 20.2-22.0.- .22 .002020000 2‘20. ..2 . 0.22.0. 1.02-0.00 . 0.00.2... 2.0002. . 0 2.2 .4400 I 00000. .110 023.222.3233l-13320020002 u 23.100 0200.20.22 2 222220.152. 00.31:. .20.... .20 00202.05: 2 .290 00200002070. 03.2 v0.39... 1.00’h20901‘os . 22. 2...)...2122... 2.. 00.322020023222122. 00: .3230023332202.0 .222 002. .2022... ...-00.313. 01.03.101.402! 2030' 0.92.0 00032202300261.10053023020 vg'wu 02. 000.12. ...2 .9000. 00. 2"..O. .W 21.22.023.022 10.30.320.000”.th: 0.03101. . 2. 2.22202. J 020.3100. 20220023032120.0000... . ‘0‘22233232028.-. . 00. 00.3 00. 30.. 200.02.? 2000 0 0050.,030-200 0,00 2...??3’02‘200020201 202002 2 . 20.0023210973250‘0 0‘0 20,} v 2’2i725. 2031.0;0J033'fvo‘0 .. .. 02 . .. 20 2 2 2 2 I 2 2.00 0‘ 2. 00.2. .... 2.20.3. .002. 2.0.3.2 0302000. 32 0On32030l13202128 .22 Q0 2 . 2 .. 2. 2 0 0. 2.. .00 . . . . .. . . 2 . . 2.022. I I. 0000 I330]. 000. 01‘... 03000. 22‘2ltu... 20200022. 30030: 2‘10I30l‘000 . . .2 2 2 I 20 ... . . 22.0 .2. . . . . . . .. . .. _ . . . . . . . . . 02.: to 2.220! t0§20‘31,023223(2.22¥ " "I . .0 20. 02.2. 2. 2 ..102 ... .. .2. 0 2. .. . . . . . . . . . . . . . 2 : . . . 02223i . 2 .2 . . . . . 2 . . . . . “2 . 2 2 ...-24003000 0.020.2l2..0.. . , «1H 1 0. 2.02. J. 00:22.: ‘30.. :2. . 2 ’l0.2o.1.020023.0t0 02 2 0.02. .32 .02.... .022 02. _ r 00?... 100.223.030.00 w. ...2 2.222 .50n124... 0 . 0.0.222. A. 3 . 222.02 2.2 .2 00 .2000 00200 .. . 2.0020222: 2,212.22“... 020. .0 .0 222.10 040 22.022.500.072... 2 r 0 . .0 2.2 2 J 0 20.202001}, 0. .2 00.310 £000.00. 2030000310002 1:320... . .2 2 no: . . .. 2 . 0. .2 0000130. 2‘ 0000?..“I202OO 30.23 202 ..I 32. 2| .2 . .. 2.2.. ...2... . . .2 .0”. . ..o ou.luw.2.2..) 2 200.1 203....032L022l 3220. 034 2 {020.22.501.22}. 2:; 00022.20. \ .12! A0... .u‘Ib.2. 020.30.332.3020': 9‘20. . . 0 SI 0200 00.00000220‘.002 3.232. .V0‘000 32...!!3‘000 22-4. .. 0‘ 0 “2. .. I 20202 0 ... I.2 ..0... ‘2 202 20-. .27... 02.0. A , ..20.’ 2'2 .2 2 . .. 2 A". 3 O .2“ 0.. 0 0 2 2|. 2 2 0 .CI >390 2 . v. . . u . .. . . 2 2 5.0.. . 0 0 0 22 n :2. . . . . aw]. 0;. up 2 . . . . 0 02 . ...... I ”I. . 2.00 0 u A a _ 0 ... . 00 .2. 0 2.22. . 0 . 2 2 .00.. 0.. 20. . 2 u 2 0 ”2.4 0 0. 0 0 2 2 0 . . 0. O .2 0 .0 0 2 2 0 .0 0 . O. . 2 2. 0 2 20 Q . 0 0 u 0. 0 0.0 .v... ..0.2.2 2 ... 2. 2 .2. .2. .2. . 2 .2. . . a . ..02. . 2 .. 0 \ ..0. . ‘ 02 . 2 0. 2 0 o . 2 I. 2 0 0.22 0.9.2 . 0 .0. ..0 2 .0 _ 2 '2 .02 .. . 2 0 . ... 2 .0 2. . . . D 0.2 0 2 0 0 2 . . 0 2 . . 2 2 2 .2 . . ... 2 . 2.. . 2 2 0 0 . v «:02 .2 0....020 ....a .0 ... . . . . .032. l .. .. _ . 0.1. "...!!IuI. 0-- ' .O ' i0 ., - 2 ' ' ., I 2 . .2 2 2 O D 2 ' n ‘ '0. I . - O 2 J 2 V .- I . . . 2. 0'1 . ... . ‘ 1 1 I 2 ‘ 0 2. . .2 b . '0 ' 2 . . 2 2 .. 2 . . 2 2 U 2 $2 0.22. 0......‘2.. .....2: .22.... I 2 0.20.0 .2 3. . 2Z0... 2.. 2. ..... f? 2 -.'§992§?§ ‘.-- 22 '02.. - 02. . ’20v00. 20. 2. 0 220 0.02. . 00.22 0. ...‘000.... 2 . 2 29...: 2. 2.2 . . .22. 0.2 3.22 .03.. .2002 ......0.0-0.0'. . 0020.00.- 0.00. .2 70.2.0 I.h2.32,222 00..." . .2. O... ..I. u. i; 0’ 2 O .../2222‘... .. 0.00 N210...“ .0. .- ..x‘..2...0.042 2. . . .2 2. .. .. .0 00.10. ...00 ...... 0 ..2 . 2 .2222. 00.0: 22.20.. . iv..- 2242.. .20 . 0'21... 2.. [0.3 2 22002002. 0 ‘0... 202052 ‘2 ‘0! 00" 0. 1.00 .2 2 2.0102020. .00.! .2 It. 0 2 . v . 20. o .0. O 0.00 2.0 v . . I a l . . 2 . .1032?! at. 1 .22 2.. .22. 0 2|. .2 .2 .0 2 2 . .00.. .0 2 02 .20... 2. ‘.0.H0020Klp.i0}.§000 D2 2\.. 0.2. 02. 20.: _ 2 l 2 .2 an 202 ..0 0 9.2.2.2 .2. . 2.2.02.2 “V202 I20 20,222.... 2002‘. .. ......IQ 40001:..52000 0 00 0.... 2. 2 . n 2 2 .. 0 .22. 0.0. ....v‘ D 0. .. .22... 0 .2 . 0.-.... 23.2 2 2 . 22.0. 2 . f. 002. .20. .. 00 02.. . 2 .... 0 2 .v . 2 I . I 20 2 I I 0' h I. l . , . . . - 2 . 2 0 . u 2. 20 0. . . . . . . . . .... .. .. . .239... .. . . . . . . 2-0 50.. . 222.22. . 2000i This is to certify that the dissertation entitled BIOMECHANICAL COMPARISON OF THREE METHODS OF BACK SQUATTING presented by Adam James Bruenger has been accepted towards fulfillment of the requirements for the Ph.D. degree in Kinesiology (lg/map; W/ Major Professor’ 5 Signature /Z7€(//w~ b/Ir /Lj Z. 00/ Date MSU is an Affirmative Action/Equal Opportunity Employer LIBRARY Michigan State University ._ -—--.-.-.—.—.- eckout from your record “.5qu r4~ 0 (i- BIOMECHANICAL COMPARISON OF THREE METHODS OF BACK SQUATTING By Adam James Bruenger A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Kinesiology 2009 Copyright by ADAM JAMES BRUENGER 2009 ABSTRACT BIOMECHANICAL COMPARISON OF THREE METHODS OF BACK SQUATTING By Adam James Bruenger The purpose of this study was to evaluate if the box squat, which is used by many high school athletes, provided any advantage in training when compared to the parallel or partial squat. Specifically, these three lifts (parallel, box, and partial) were evaluated for differences in: (a) joint/body segment angles (ankle, knee, and lower back) at the lowest point of descent; (b) joint forces and moments (ankle, knee, hip, and lower back) at the lowest point of descent; (c) muscle activity (as measured by electromyography) for the muscles believed to be primarily recruited during squatting (rectus femoris, vastus lateralis, gastrconemius, biceps femoris, gluteus maximus, and erector spinae); ((1) recovery of power, measured by maximal vertical jumps 15 minutes and 3 hours after a workout; and anaerobic endurance, measured by a 80300 jump test 3 hours after a workout, and (e) ratings of perceived exertion (RPE) as measured by a modified ten point Borg scale. Seventeen weight trained male athletes (age: 16.8i1.4 years; box squat experience: 2.4i1.8 years; parallel squat experience: 2.4i1.7 years) participated in this study. Each participant completed two preliminary sessions followed by three workout sessions. Each session was a minimum of 48 hours and a maximum of three weeks apart. Each workout session consisted of performing three sets of 10 repetitions of either parallel, box, or partial squat using the same absolute weight. The workouts were counterbalanced to prevent an order of testing effect. Participants exhibited significantly different (p<.05) joint angles (ankle, knee, and lowerback), lower forces and moments (ankle, knee, hip, and lower back), and lower, normalized, average muscle activity (rectus femoris, vastus lateralis, biceps femoris, and erector spinae) when performing box squats compared to either the parallel or partial squats. However, only the decrease in maximum vertical jump height after the performance of parallel squats was significantly different (p<.05) than the decrease in maximum vertical jump height after the performance of box or partial squats. Participants also perceived the parallel squat workouts to be more intense than either the box or partial squat workouts (p<.05), but there was not a significant difference in perceived exertion between the box and partial squat workouts. Furthermore, performance of the parallel squat created greater moments at the knee and hip (p<.05), but not greater normalized, average muscle activity when compared to the partial squat. There was no significant difference in anaerobic endurance, compared to a non-fatigued reference test, three hours after completion of any of the three workouts (parallel, box and partial squat). These results show that the box squat; when performed using the same absolute intensity, volume, and recovery; does not provide any faster recovery than either the parallel or partial squat. Furthermore, average muscle activity was lower when performing the box squat compared to the parallel and partial squat. This lower average muscle activity may lead to less training adaptation over time. Thus, it does not appear that the box squat provides any advantage over either parallel or partial squats. Furthermore, if an alternative lift to the parallel squats is desired to allow for more weight to be used in training, the partial squat appears to be an appropriate alternative to the box squat. ACKNOWLEDGEMENTS First, I would like to thank my committee: Dr. Eugene Brown, Dr. Gail Dummer, Dr. Roger Haut, and Dr. Mark Reckase for their support, help, guidance, and patience. Second, I would like to thank all my friends for their help. Jerrod Braman, Ryan Francis, Keke Yang, Mark Villwock, and Tony Moreno thank you for helping with data collection. The dissertation would never have been completed without your time and efforts. Kimbo,. thanks for helping with the behind the scene aspects and being willing to help when needed. I also would like to thank Ken Mannie and Mike Vorkapich for letting me borrow testing equipment from the athletic department. Finally, I would like to thank my my family: my children, J oslyn and Sebastian, for letting me work when you really wanted to play, and my wife, Jennifer, for all the love and support she has provided and for what she has sacrificed to allow me to complete my degree. TABLE OF CONTENTS LIST OF TABLES ............................................................................................................. ix LIST OF FIGURES .......................................................................................................... xii CHAPTER 1 ....................................................................................................................... 1 INTRODUCTION .............................................................................................................. 1 Overview ..................................................................................................................... 1 Recovery ................................................................................................................. 7 Hip Development .................................................................................................... 9 Significance of the Problem ...................................................................................... 10 Statement of the Problem .......................................................................................... 1 1 Need for the Study .................................................................................................... 12 Research Questions ................................................................................................... 13 Hypotheses ................................................................................................................ 14 Limitations ................................................................................................................ 1 5 Assumptions .............................................................................................................. 16 Definitions ................................................................................................................. 16 CHAPTER 2 .............................. ' ....................................................................................... 22 REVIEW OF LITERATURE ........................................................................................... 22 Overview of the Box Squat ....................................................................................... 23 The Box Squat ....................................................................................................... 23 Safety Concerns of Strength Training and the Box Squat .................................... 30 Analysis of Weight Training Technique ................................................................... 34 EMG Evaluation ................................................................................................... 34 Kinematic and Kinetic Analysis ........................................................................... 47 RPE and Intensity ................................................................................................. 54 Effect on Tests of Performance ............................................................................. 57 Evaluation of Weight Training Protocols ................................................................. 59 CHAPTER 3 ..................................................................................................................... 63 METHODS ....................................................................................................................... 63 Research Design ........................................................................................................ 63 Participants ................................................................................................................ 64 Selection Criteria ...................................................................................................... 65 Recruitment ............................................................................................................... 65 Sample Size ............................................................................................................... 66 Instrumentation ......................................................................................................... 67 EMG ...................................................................................................................... 67 Motion Analysis .................................................................................................... 7O Force Platforms ..................................................................................................... 77 Anthropometric Measurements ............................................................................. 78 vi Vertec .................................................................................................................... 81 Bosco Jump Test ................................................................................................... 82 Borg Scale ............................................................................................................. 86 Testing Procedures .................................................................................................... 88 Session One-Familiarization and IORM Testing .................................................. 90 Session Two- Reference Bosco J urnp Test ......................................................... 102 Sessions Three through Five ............................................................................... 103 Squat Lift Techniques ......................................................................................... 107 Data Analysis .......................................................................................................... 108 EMG .................................................................................................................... 108 Motion Analysis and Force Platform Data ......................................................... 109 Vertec .................................................................................................................. 126 Bosco Jump Test ................................................................................................. 126 Borg Scale ........................................................................................................... 127 Data Management ................................................................................................... 127 CHAPTER 4 ................................................................................................................... 128 RESULTS ....................................................................................................................... 128 Participants’ Characteristics .................................................................................... 128 Research Questions ................................................................................................. 131 RQl. How do the joint angles of the ankle and knee, and orientation of the lower back, at the lowest point of descent, differ among the three squat lifts (parallel, box, and partial squat)? ................................... 131 RQ2. How do the forces and moments, calculated using a two dimensional model, at the ankle, knee, and hip joints, as well as the forces and moments experienced in the lumbar region, differ among the three squat lifis at the lowest point of descent? ...................... 135 RQ3. How does recruitment of the vastus lateralis, rectus femoris, biceps femoris, gluteus maximus, gastrocnemius, and erector spinae muscles differ among the three squatting lifts (parallel, box, and partial)? ...................................................................... 146 RQ4. Is there a relationship among the electrical activity of selected muscles and the forces and moments experienced at the lowest pointof descent? ....................................................................................... 170 RQS. How do selected performance parameters (maximum vertical jump and anaerobic endurance as measured by a Bosco jump test) of participants change due to completing workouts of the three different squatting exercises? ................................................................................. 170 RQ6. How do participants’ perceived effort, immediately after bouts of the three different squat exercises, differ? ............................................... 176 RQ7. Is there a relationship between participants’ perceived effort and the rate of recovery? ................................................................................. 179 CHAPTER 5 ................................................................................................................... 180 DISCUSSION ................................................................................................................. 180 Minimizing Threats to Validity .............................................................................. 180 vii Minimizing Threats to Internal Validity .............................................................. 180 Minimizing Threats to External Validity ............................................................ 184 Research Questions ................................................................................................. 184 RQl. How do the joint angles of the ankle and knee, and orientation of the lower back, at the lowest point of descent, differ among the three squat lifis (parallel, box, and partial squat)? ................................... 184 RQ2. How do the forces and moments, calculated using a two dimensional model, at the ankle, knee, and hip joints, as well as the forces and moments experienced in the lumbar region, differ among the three squat lifts at the lowest point of descent? ...................... 187 RQ3. How does recruitment of the vastus lateralis, rectus femoris, biceps femoris, gluteus maximus, gastrocnemius, and erector spinae muscles differ among the three squatting lifts (parallel, box, and partial)? ....................................................................... 191 RQ4. Is there a relationship among the electrical activity of selected muscles and the forces and moments experienced at the lowest point of descent? ....................................................................................... 194 RQS. How do selected performance parameters (maximum vertical jump and anaerobic endurance as measured by a Bosco jump test) of participants change due to completing workouts Of the three different squatting exercises? .................................................................................. 195 RQ6. How do participants’ perceived effort, immediately after bouts of the three different squat exercises, differ? ................................................ 197 RQ7. Is there a relationship between participants’ perceived effort and the rate of recovery? ................................................................................. 197 Implications for Coaches and Athletes .................................................................... 198 Future Research ....................................................................................................... 199 Limitations ............................................................................................................... 201 APPENDIX A IRB Applications and Consent/Assent Forms ......................................................... 203 APPENDIX B Questionnaires and Data Collection Sheets ............................................................. 224 APPENDIX C ‘ Inter- and Intratester Evaluation of Anthropometric Measurements ....................... 234 APPENDIX D Order of Workout Sessions ..................................................................................... 239 APPENDIX E Squat Model Validation ........................................................................................... 241 BIBLIOGRAPHY ........................................................................................................... 254 viii Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8 Table 9 Table 10 Table 11 Table 12 Table 13 Table 14 Table 15 Table 16 Table 17 LIST OF TABLES Summary of EMG Evaluations of Squatting Exercises ................................... 42 Summary of Kinematic Evaluations of Squatting ........................................... 50 Scale for Ratings of Perceived Exertion (Modified Borg Scale) ..................... 56 Scale for Ratings of Perceived Exertion (Modified Borg Scale) ..................... 87 Outline‘of Experimental Sequences and Procedures ....................................... 88 Temporal and Sequential Order for 10RM Testing (Modified from Baechle & Earle, 2000) .......................................................... 99 Dempster’s Body Segment Parameters (as found in Robertson et a1., 2004) ............................................................... 118 Characteristcs of Participants (N=17) ............................................................ 130 Multivariate Analysis of Variance for the Joint Angles at the Lowest Point of Descent (N=16) ................................................................................ 133 Analysis of Variance for the Joint Angles at the Lowest Point of Descent (N=16) .............................................................................................. 133 Tukey Post-hoc Values for Joint Angles (N=16) .......................................... 134 Multivariate Analysis of Variance for the Horizontal and Vertical Forces of the Ankle and Lower Back at the Lowest Point of Descent (N=16) ......... 136 Analysis of Variance for the Ankle and Lower Back Reaction Force Data at the Lowest Point of Descent (N=16) ....................................... 136 Tukey Post-hoc Values for Ankle Joint Reaction Forces (N=16) ................. 139 Tukey Post-hoc Values for Low Back Reaction Forces (N=16) ................... 140 Multivariate Analysis of Variance for the Joint Moments at the Lowest Point of Descent (N=16) ................................................................................ 143 Analysis of Variance for the Joint Moments at the Lowest Point of Descent (N=16) ......................................................................................... 143 ix Table 18 Table 19 Table 20 Table 21 Table 22 Table 23 Table 24 Table 25 Table 26 Table 27 Table 28 Table 29 Table 30 Table 31 Table 32 Table 33 Table 34 Table 35 Tukey Post-hoc Values for Joint Moments (N=16) ....................................... 144 Analysis of Variance for the Session EMG Data as a Percent of Total Muscle Activity (N=16) ................................................................................. 150 Analysis of Variance for the EMG Data as a Percent of Total Muscle Activity (N=16) .............................................................................................. 155 Tukey Post-hoe for the EMG Data as a Percent of Total Muscle Activity (N=16) .............................................................................................. 157 Analysis of Variance for the EMG Data Normalized to Reference Test Session Check (N=16) ........................................................................... 160 Analysis of Variance for the EMG Data Normalized to Reference Test (N =1 6) .................................................................................................... 165 Tukey Post—hoe Values for the EMG Data Normalized to Reference Test (N =1 6) .................................................................................................... 167 Analysis of Variance for Order Effect of Difference from Pre-Workout Vertical Jump (N=17) .................................................................................... 171 Analysis of Variance for Order Effect of Bosco Jump Test (N=17) ............. 171 Analysis of Variance for Vertical Jump Post—workout (N=17) ..................... 174 Tukey Post-hoc Values for Vertical Jump Post-workout (VJ 15 and VJ 180 Combined) (N=17) .......................................................... 174 Analysis of Variance for Bosco Jump Test (N=17) ....................................... 176 Analysis of Variance for Order of Workout Comparison of Perceived Exertion. (N=17) ............................................................................................ 177 Analysis of Variance for Workout Condition Comparison of Perceived Exertion. (N=17) ............................................................................................ 177 Tukey Post-hoe Values for Perceived Exertion (N=17) ................................ 178 Pearson Correlations Comparing RPE to Recovery ...................................... 179 Inter- and Intratester Comparisons ................................................................ 236 Intraclass Correlation Coefficients for Inter- and Intratester Reliability ....... 238 Table 36 Table 37 Table 38 Random Assigned Orders of Workouts ......................................................... 240 Summation of Reaction Forces for a Single Participant at One Given Time Frame .................................................................................................... 243 Comparison of BodyBuilder Joint Moment Values Compared to Excel Calculations .................................................................................................... 244 xi LIST OF FIGURES Figure 1. Example of a parallel squat. ............................................................................... 4 Figure 2. Example of a box squat without plantar flexion at the end of ascent. ................ 5 Figure 3. Example of a box squat with plantar fiexion at end of ascent. ........................... 5 Figure 4. Example of a partial squat. ................................................................................. 6 Figure 5. Back squat starting position in which the barbell is supported behind the neck. ............................................................................................... 24 Figure 6. Anterior frontal plane view of EMG electrode placement and portable belt unit. ............................................................................................. 68 Figure 7. Sagittal plane view of EMG electrode placement and position of two force platforms ...................................................................................... 69 Figure 8. Posterior frontal plane view of EMG electrode placement and portable belt unit .............................................................................................. 70 Figure 9. Arrangement of infrared cameras and force platforms for data collection. ..... 71 Figure 10. Arrangement of infrared cameras, Vicon computer, and force platform amplifiers. ...................................................................................................... 72 Figure 11. Anterior frontal plane view of reflective marker placements ......................... 74 Figure 12. Sagittal plane view of reflective marker placements. ..................................... 75 Figure 13. Force platforms and calibration wand at global reference point. ................... 76 Figure 14. Arrangement of force platforms and adjustable box for box squat session. .. 78 Figure 15. Maximum reach test using a Vertec. .............................................................. 83 Figure 16. Participant performing maximal vertical jump test using a Vertec. ............... 84 Figure 17. Proper jump depth for the Bosco jump test. ................................................... 85 Figure 18. Calf stretch ...................................................................................................... 91 xii Figure 19. Figure 20. Figure 21. Figure 22. Figure 23. Figure 24. Figure 25. Figure 26. Figure 27. Figure 28. Figure 29. Figure 30. Figure 31. Figure 32. Figure 33. Figure 34. Figure 35. Figure 36. Figure 37. Standing quadriceps stretch. ........................................................................... 92 Gluteus maximus stretch. ............................................................................... 93 Hip flexor stretch. ........................................................................................... 94 Groin stretch. .................................................................................................. 95 Hamstring stretch ............................................................................................ 96 Example of proper bungee cord placement so that the top of the thighs are parallel to the ground at the low point in the squat .................................. 98 Proper box squat depth. ................................................................................ 101 Comparison of lowest point of descent for (a) box, (b) parallel, and (c) partial squats. .......................................................................................... 102 Henne dye markers showing the perimeter of the pairs of electrodes used on the vastus lateralis and rectus femoris ............................................ 106 Five segment sagittal plane model to evaluate joint angles and forces and moments of the low back and right ankle, knee, and hip. .......... 111 Virtual points (knee center and hip) in comparison to reflective markers. .. 1 14 Local coordinate systems of the foot and shank ........................................... 115 Determination of lower back angle offset. ................................................... 116 Determination of knee angle offset. ............................................................. 117 Quasi-static model of the foot to calculate ankle reaction forces and moments for all squats. ................................................................................ 120 Quasi-static model of the shank to calculate knee reaction forces and moments for all squats. ................................................................................ 121 Quasi-static model of the thigh to calculate hip reaction forces and moments for all squats. ................................................................................ 122 Quasi-static model of the pelvis to calculate low back reaction forces and moments for the parallel, partial, and Box2 squats. .............................. 123 Quasi-static model of the pelvis to calculate low back reaction forces and moments for the Boxl squat. ................................................................ 124 xiii Figure 38. Figure 39. Figure 40. Figure 41. Figure 42. Figure 43. Figure 44. Figure 45. Figure 46. Figure 47. Figure 48. Figure 49. Figure 50. Figure 51. Figure 52. Means and standard deviations ($03) of joint angles at the lowest point of descent. ........................................................................................... 132 Means and standard deviations ($03) of horizontal forces normalized to body weight at the lowest point of descent. .......................... 137 Means and standard deviations (SDs) of vertical forces normalized to body weight at the lowest point of descent. .......................... 138 Means and standard deviations (SDs) of joint moments at the lowest point of descent. ........................................................................................... 142 Typical rectified EMG pattern for single repetition of (a) parallel and (b) box squat. ......................................................................................... 147 Means and standard deviations (SDs) of eccentric muscle activity as a percent of total muscle activity (outliers retained in the analysis). ........... 151 Means and standard deviations (SDs) of eccentric muscle activity as a percent of total muscle activity (outliers removed from the analysis) ....... 152 Means and standard deviations (805) of concentric muscle activity as a percent of total muscle activity (outliers retained in the analysis). ........... 153 Means and standard deviations (SDs) of concentric muscle activity as a percent of total muscle activity (outliers removed from the analysis) ....... 154 Means and standard deviations (SDs) of eccentric muscle activity normalized to reference test (outliers retained in the analysis) .................... 161 Means and standard deviations (SDs) of eccentric muscle activity normalized to reference test (outliers removed from the analysis) .............. 162 Means and standard deviations (SDs) of concentric muscle activity normalized to reference test (outliers retained in the analysis) .................... 163 Means and standard deviations (SDs) of concentric muscle activity normalized to reference test (outliers removed from the analysis) .............. 164 Means and standard deviations (SDs) of the decreases in vertical jump height from pre-workout at 15 minutes and 180 minutes post-workout. ..... 173 Means and standard deviations (SDs) comparison of anaerobic endurance as measured with the Bosco jump test. ....................................... 175 xiv Figure 53. Means and standard deviations ($05) of average set RPE values after the three workout conditions using the modified Borg scale. .............. 178 XV CHAPTER 1 INTRODUCTION Overview Weight training is viewed as an important tool to improve athletic performance and to prevent injury (Faigenbaum & Micheli, 1998; Kraemer et al., 2000). It is often suggested that weight training should be emphasized during the off-season while a weight training maintenance program should be used during the in-season (Fleck & Kraemer, 2004). The intensity and volume of a weight training program need to be modified during an athletic season to allow for recovery from the stresses of the actual sport. Consequently, this time frame of weight training is often referred to as a maintenance phase because the goal is to maintain the strength levels achieved during the off-season. Failure to maintain a weight training program during the course of an athletic season has been shown to result in decreases in strength (Campbell, 1967; Hoffman, Fry, Howard, Maresh, & Kraemer, 1991). Many athletic programs include weight training twice a week during the maintenance phase (Fleck & Kraemer, 2004). However, high school coaches, especially those whose sports have multiple competitions per week, may find it difficult to schedule time for weight training during the season. This difficulty is related to the potential adverse effects of an acute bout of weight training on performance in an upcoming competition (Woolstenhulme, Bailey, & Allsen, 2004). Due to this concern, coaches often will not maintain a regular weight training schedule for their athletes during the competition season or will search for alternative methods/programs of weight training, that promise to minimize fatiguing effects, for their athletes. One such alternative program of weight training that is marketed to high school coaches is the Bigger, Faster, Stronger (BF S) program. BF S is also the name of an organization that provides weight training education to individuals involved in high school athletic programs across the United States in the form of workout programs for athletes, clinics for coaches and athletes, and certification programs for coaches. Promotional literature for BF S states that over 9,000 high school athletic programs have implemented their weight training program and that BFS has been a weight training consultant for many professional teams, such as the Green Bay Packers of the National Football League and Utah Jazz of the National Basketball Association (Shepard, 2004b). The BFS program is philosophically different from many other marketed programs and/or typical weight training methods used in high school athletic programs. Many high school athletic weight training programs vary the intensity of workouts during a week, both in- and out of season, by having a “heavy” day and a “moderate or light” day of weight training to reduce the total amount of fatigue and allow for full recovery from the training (Arthur & Bailey, 1998; Baechle & Earle, 2000; Fleck & Kraemer, 2004). Heavy days are often scheduled when there are several days between a weight training session and a competition, while the moderate or light training occurs when there are only a few days between the two. Moderate or light days may consist of less weight being used per set, reduction in the number of sets and repetitions performed, or a combination of both variations when compared to the heavy workout days. The BFS program, however, chooses to use different exercises as a means of weight training stimulus variation instead of changing intensity and volume. An example of this variation of lifts used in the BFS program for the lower extremity would be that parallel squats (Figure 1) are performed when there are several days between weight training and competition while box squats (Figures 2-3) are performed when there are few days between weight training and competition. Parallel squats consist of athletes descending to a depth where the tops of the thighs are parallel with the floor. At this point, the athletes would then ascend back to the starting position. Box squats consist of athletes descending onto a box that is high enough to put them into a position with the tops of their thighs slightly above parallel (Shepard, 2004a, 2004c, 2004d). The athletes come to a complete stop in their descent by sitting on the box, and then ascend back to the starting position. This style of squat has been advocated by BFS to be performed with plantar flexion of the ankles at the end of the lift (Figure 3) or without plantar flexion (Figure 2). This style of squat is very similar to what is often referred to as a partial squat in which athletes pause (Figure 4) for a moment when the knees reach an angle of flexion of approximately 90 degrees to mark the end of the their descent (end of eccentric phase). After this momentary pause, the performer lifts the weighted bar back to the starting position (concentric phase). A difference between the partial squat and the box squat occurs during the transition phase from descent to ascent. During the pause in the partial squat, athletes must maintain this position via isometric contraction of the ankle plantar flexors and knee, hip, and spinal extensor muscles. In contrast, the performance of the box squat may permit the plantar flexors of the ankles and the extensors of the knees and hips to substantially reduce their force of isometric contraction. In both of these lifts, during the transition from descent to ascent, the spinal extensors are called upon tO support the weight Of the body above the hip joint and the weight being lifted. (a) (b) (C) Figure 1. Example of a parallel squat. (a) Start, (b) maximum descent or end of eccentric phase, (c) end of ascent or end of concentric phase. (a) (b) (C) Figure 2. Example of a box squat without plantar flexion at the end of ascent. (a) Start, (b) maximum descent or end of eccentric phase, (c) end of ascent or end of concentric phase. (a) (b) (C) ~+’-" ‘ :- nth-«MI "' Figure 3. Example Ofa box squat with plantar flexion at end Of ascent. (a) Start, (b) maximum descent or end of eccentric phase, (c) end of ascent or end Of concentric phase. (a) (b) (C) Figure 4. Example of a partial squat. (a) Start, (b) maximum descent or end Of eccentric phase, (c) end of ascent or end of concentric phase. BF S and other proponents of box squats believe that box squats are beneficial to strength development. They suggest that athletes are able to lift more weight performing a box squat than a parallel squat because of the mechanical advantage created by not descending as deep in the box squat and also, possibly, because a lesser isometric force is exerted in the performance of the box squat during the transition from the eccentric to concentric portion of the lift to control the same load. The BF S program suggests that no more than 100 to 150 additional pounds should be used when box squatting compared to what is normally used during a parallel squat workout (Shepard, 2004a, 2004c, 2004d). Additionally, proponents state that one of the main benefits of using box squats is that recovery after a similar workout, in terms of volume and relative intensity, is much quicker than from the use of regular parallel squats, even though an athlete used more weight in the box squat (Shepard, 2004a, 2004c, 2004d; Simmons, 1998). It is believed that because of this faster recovery, box squats can be used the day before an athletic contest without adversely affecting performance in the contest (Shepard, 2004a, 2004c). Finally, box squats are believed to be beneficial in developing “the hips” to a greater extent than parallel squats (Goss, 2004; Shepard, 2004a, 2004c, 2004d; Simmons, 1998). Recovery What is meant by faster recovery is not well defined in the BF S literature. Acute neuromuscular fatigue that occurs as a result of weight training can be due to decreased neural activity (central fatigue) and may be evidenced by a decreased force production of the muscles (peripheral fatigue) (Woolstenhulme et al., 2004). The reasons for the conjectured faster recovery that is said to occur when weight training via box squats in comparison to weight training via partial or parallel squats has not been established in research literature. Three questions need to be answered: (a) Is there a faster recovery from weight training via box squats in comparison to similar training, in terms of sets and repetitions, via parallel or partial squats? (b) If athletes recover more quickly from training via box squats in comparison to similar training via parallel or partial squats, what are the reasons for this response? (c) If faster recovery exists, is it due to differences in recruitment of muscles, neurological fatigue, physiological response to the exercises that result in varying peripheral fatigue, and/or muscle damage? The few studies, examining the time rate of recovery after weight training, suggest that a “moderate weight training protocol” would not affect game performance given relatively short recovery times between the weight training session and the athletic competition (Kauranen, Siira, & Vanharanta, 1999; Raastad & Hallen, 2000; Schoenfelt, 1991; Woolstenhulme et al., 2004). Quantification of a moderate training protocol is difficult because many researchers have defined it differently; however, it is often considered to be the performance of multiple sets (three-four) using an 8 to 12 repetition maximum (RM) or performance of 8 to 12 repetitions using 67 to 80% of 1 repetition maximum (1RM)(Baechle & Earle, 2000). For example, Kauranen et al.’s (1999) study of untrained women showed no change in motor performance as measured by reaction time, speed of movement, tapping speed, and coordination immediately after acute neuromuscular fatigue was produced by a circuit workout. The circuit workout consisted of 12 exercises where three sets of 15RM were performed for each exercise. Likewise, Raastad and Hallen (2000) observed recovery of knee extension strength and jump squat performance three hours after a bout of moderate intensity exercise with strength trained men. The moderate workout in this training protocol was defined as three sets of three repetitions using 70% of 3RM for back squats and front squats and three sets of six repetitions using 70% of 6RM for leg extension. Schoenfelt (1991) found no significant decrease in free throw performance immediately after a weight training session performed by collegiate women. Finally, Woolstenhulme et al. (2004) observed that vertical jump, power output as measured with a Wingate test, and basket shooting accuracy as measured with a multiple position shooting test were equivocal to rested performances six hours after a total body weight training session performed by female collegiate basketball players. The protocol in this experiment consisted of three to four sets of 8-12RM for seven exercises (hang clean, push jerk, bench press, back squat, overhead press, prone leg curl, and dumbbell incline press). These studies would suggest that, at a moderate intensity, weight training with box squats would not be any more or less advantageous in subsequent athletic activity than any other type of moderate intensity weight training protocol for the lower extremity. However, no known studies have looked at the recovery rate of high school athletes after an acute bout of weight training of the lower extremity using box squats, partial squats, or parallel squats. Hip Development Bigger Faster Stronger does not specify which muscles they are referring to when they talk about greater “hip” development from performing box squats compared to other squat exercises and data supporting/refuting this claim is limited. Other statements allude to the notion that the amount of gluteal involvement is greater in box squats compared to parallel squats. The suggested greater gluteal involvement by performing box squats is in conflict with research done by Caterisano et a1. (2002), who observed that the electromyographic (EMG) activity of the hip extensors, primarily the gluteus maximus, increased with a larger descent during regular squats (ie., parallel squats had more gluteal activity than partial squats when analyzed as a percent of total muscle activity). Caterisano et al.’s study would suggest that the box squat, in which the descent is similar to the partial squat and not as deep as the parallel squat, would have less gluteal recruitment. No known studies have been performed to evaluate hip extensor activity via EMG for box squats compared to parallel or partial squats. Additionally, no known studies have examined the muscle recruitment changes in the back extensors and the lower extremity muscles during the performance of squats with different levels of depth associated with different amounts of maximal knee flexion. Significance of the Problem The profession of weight training is inundated with training techniques that are believed to isolate specific muscles or provide a specific training stimulus. Previous research has refuted commonly held beliefs of weight training such as a wider grip in the bench press significantly increases the activity of the pectoral muscles (Barnett, Kippers, & Turner, 1995; Cogley et al., 2005), adjusting the position of the feet can significantly change the emphasis of quadriceps muscle activity during squatting (Signorile, Kwiatkowski, Caruso, & Robertson, 1995), and weight training should not be performed on the same day as a competition (Woolstenhulme et al., 2004). However, research has supported some training beliefs such as the triceps muscle becomes more active during close grip bench presses in comparison to wide grip bench presses (Barnett et al., 1995) and wide grip lat-pull down exercises more effectively engage the latissimus dorsi in comparison to narrow grip lat-pull down exercises (Signorile, Zink, & Szwed, 2002). The proposed benefits of performing box squats (i.e., faster recovery, greater hip development) is another one of these training beliefs that has not yet been scientifically evaluated. Predictions of what would be expected from box squats can be gleaned from studies of squatting to different depths (Caterisano et al., 2002; Wretenberg, Feng, Lindberg, & Arborelius, 1993) and with the use of different weights (McCaw & Friday, 1994). However, no know studies have specifically evaluated the box squat to determine if there is faster recovery or greater development of the hip extensors. Many of these untested training beliefs, including the performance of box squats, are practiced in high school weight training programs. BFS cites a study performed at the University of Minnesota in which 40% of all high school football coaches polled stated 10 that their primary source of weight training information was through BFS (Shepard, 20043). Currently, over seven million students participate in high school athletics (NFHS, 2008). Unfortunately, census data does not provide exact amounts of how many of these high school athletes weight train as part of their athletic training program. However, BFS claims that over 9,000 high schools use their program and over 250 clinics are performed each year for high school athletes by BFS staff (Shepard, 2004b, 2004d). Over half a million athletes have participated in these clinics and over one million athletes have used or currently are using the BFS program (Freebom, personal communication, 2006). Statement of the Problem The overall purpose of this study was to evaluate if the proposed benefits of box squatting, compared to parallel or partial squatting, are valid. Specifically, the purposes of this study was to: (a) compare the kinematics and kinetics at the ankle, knee, hip, and lower back throughout these lifts; (b) evaluate the differences in recruitment patterns and activation of the muscles primarily thought to be involved in squatting (vastus lateralis, rectus femoris, biceps femoris, gluteus maximus, gastrocnemius, and erector spinae) during acute performances by volunteers of the three lifts (parallel, box, and partial squat); (c) evaluate the difference in various performance parameters (maximal vertical jump and anaerobic endurance as evaluated by a Bosco jump test (Bosco, Luhtanen, & Komi, 1983) after bouts of parallel squats, box squats, and partial squats; and (d) compare these parameters to perceived exertion and fatigue as measured by the modified Borg scale (Foster et al., 2001). ll Need for the Study Unanswered questions about the proposed benefits of box squats raised a concern for the use of this method of weight training by high school athletes. Concerns about the safety of box squats and their effect on the lower back have been expressed (Brown, 1998 & 2003), but proponents state that with proper technique, box squats are as safe as any other squat (Goss, 2004; Shepard, 2004a, 2004c, 2004d; Simmons, 1998). Without scientific evaluation and publication of the potential benefits and/or potential detriments of such lifts, coaches of athletes are left to make uninformed or even falsely informed choices about incorporating such lifts into their athletes’ weight training programs. Coaches must then make decisions based on conflicting testimony, about such programs as BF S, on the basis of anecdotal evidence to both their potential benefits and potential detriments (Goss, 2004; Shepard, 20043, 20040; Simmons, 1998). Furthermore, many of the current athletes that use box squats will become future coaches. Since sport often maintains its traditions, these athletes who become coaches are likely to use the same weight training techniques that they used as athletes. This “academic inertia” may perpetuate the use of such unproven lifts. Because this technique is taught to thousands of high school athletes each year, it is imperative that a thorough investigation was done to examine if box squats provide any advantage or detriment compared to other methods of performing squat lifts. 12 Research Questions This study was conducted to answer the following research questions about high school athletes performing the three squats in question (parallel, box, and partial): RQ1. RQ2. RQ3. RQ4. RQ5. How do the joint angles of the ankle and knee and orientation of the lower back, at the lowest point of descent, differ among the three squat lifts (parallel, box, and partial squat)? How do the forces and moments, calculated using a two dimensional model, at the ankle, knee, and hip joints, as well as the forces and moments experienced in the lumbar region, differ among the three squat lifts at the lowest point of descent? How does recruitment of the vastus lateralis, rectus femoris, biceps femoris, gluteus maximus, gastrocnemius, and erector spinae muscles differ among the three squatting lifts (parallel, box, and partial)? a. How does the sequencing of muscle activity differ throughout the squat lifts? b. How does the percentage contribution of total muscle activity differ throughout the squat lifts? c. How does the electrical activity of the muscle differ throughout the three squat lifts when normalized to a reference activity? Is there a relationship among the electrical activity of selected muscles and the forces and moments experienced at the lowest point of descent? How do selected performance parameters (maximum vertical jump and anaerobic endurance as measured by a Bosco jump test) of participants change due to completing workouts of the three different squatting exercises? a. Does maximum vertical jump height differ after a bout of exercise? 13 RQ6. RQ7. b. How does a participant’s ability to perform a Bosco jump test change with different training protocols? How do participants’ perceived effort differ immediately after bouts Of the three different squat exercises? Is there a relationship between participants’ perceived effort and the rate of recovery? Hypotheses The following hypotheses were proposed for this study with regard to the high school athletes in question: H1. H2. H3. H4. H5. H6. There will be differences in joint angles (ankle, knee, hip, and lower back) at the lowest point of descent between the three modes of squatting. The moments at the hip and knee, as calculated using a two dimensional model, will differ at the lowest point of descent between the three modes of squatting, mainly due to the joint angles being different. The muscle activity (both relative activity and percent muscle contribution) will differ between the three modes of squatting. As the forces and moments increase, there will be an increase in muscle activity. The rate of recovery, as measured by the maximum vertical jump and Bosco jump test, will differ, both at the 15 minute test and three hour test, following the three modes of squatting. Athletes will report that their exertion levels differed among exercise sessions. 14 H7. Athletes will have less recovery (as measured by the change in maximal vertical jump and power output measured by the Bosco jump test) when their perceived effort is higher. Limitations The participants in this study were high school athletes or college students (freshmen or sophomores) who had at least one year of weight training experience and at least six months of experience using the box squat and parallel squat as part of their weight training protocol. These participants may not be representative of all athletes that perform different methods of squatting in their workouts. Athletes unfamiliar with the techniques being used or with lower levels of overall training could have different biomechanical performance parameters and physiological responses. A particular technique (style) of box squatting was being evaluated. This technique wOuld not fully represent the multitude of variations that could be performed as a representation of box squatting. However, the technique used was the most prevalently suggested in the literature on the subject of performing box squats. The process of evaluating the lifts and standardizing movements may have changed how the athletes performed the lifts during the testing compared to how they normally performed the lifts during their weight training programs. 15 neck. Assumptions The subjects have bilateral symmetry in the sagittal plane in their movement and forces produced during the course of performing the three squat lifts. All movements during the squat lifts occur in the sagittal plane. It is appropriate to model the body as a five link (foot, shank, thigh, pelvis, trunk) rigid system. It is appropriate to model the joints as frictionless and hinged (Brown & Abani, 1985) The feet will remain planted on the floor during the entire lift. It is appropriate to consider the movements during all lift as slow and constant such that a “quasi-linear”/“semi-dynamic” method of evaluation, where segmental linear and angular accelerations are equal to zero, does not substantially alter the kinetic results (Wretenburg et al., 1993). Definitions Acute performance. A single workout session of an exercise. Back squat. A squat lift where a barbell is supported on the shoulders behind the Box squat. A squat lift that consists of an athlete descending onto a box that is high enough to put the athlete into a position with the tops of the thighs slightly above parallel to the ground when seated on a box (Shepard, 2004a, 2004c, 2004d). The athlete comes to a complete stop, sits on the box, and then ascends back to the starting position (Figure 2). l6 Central fatigue. Attenuation of the force response of contracting muscles due to failure in the central nervous system as opposed to failure at the muscle or other factors in the activation that lie outside the central nervous system (N i gg, Maclntosh, & Mester, 2000) Concentric. Muscle is shortening during the contraction (Fleck & Kraemer, 2004). It has also been defined as when the force of resistance is less than the force of the contraction. Closed chain exercises. Exercises where the terminal joint is restrained from free motion (Baechle & Earle, 2000). Deadlift. Weight training or weightlifting exercise where a person stoops forward to lift a barbell from the ground until he/she is in a standing position and the lower extremities and trunk are completely extended. Eccentric. Muscle is lengthening in a controlled manner during its contraction (Fleck & Kraemer, 2004). It has also been defined as when the force of resistance is greater than the force of contraction. Electromyography (EMG). Measurement of a muscle’s electrical activity. Front squat. A squat lift where the bar is held in front of the neck. Full squat. A squat lift where a person descends until the back of the thighs are in contact with the calves. The person then ascends to the starting position. Half squat. Another name for partial squat. l7 Heavy, medium, and light workouts. Methods used to vary the intensity of the workout during the course of a week. Use of heavy, medium, and light workout days will depend on the number of workouts per week and the goals of the workout. Heavy days often consist of performing sets to failure. Medium days often use 85-90% of the weight used on heavy workout days while light workout days often use 70-80% of the weight used on heavy workout days. Medium and light workout days can also be produced by maintaining the intensity but reducing the volume (number of sets and/or repetitions). Intensity. Level of muscle activity that can be quantified in terms of power (Baechle & Earle, 2000). Alternatively, effort expended during training (Baechle & Earle, 2000). Isokinetic. Movement occurs without acceleration (at constant velocity). Isometric. No movement occurs at the joint, but force is produced by the muscle to maintain joint angle (Fleck & Kraemer, 2004). Kinematic. Evaluation of movement with respect to time. Kinetic. Study of the action of forces. Learning eflect. An increase in performance due to having performed the test previously. Linear envelope. Method of quantifying an EMG signal where the electrical activity is full wave rectified and a low pass filter is then used on the signal. This method “is a type of moving average indicator of EMG magnitude” (Robertson, Caldwell, Hamill, Karnen, & Whittlesey, 2004, p. 172). Maximal voluntary isometric contraction. Measurement of the electrical activity of a muscle while the muscle is isometrically contracted. 18 Multiple repetition maximum (XRM). The maximum amount of weight that can be lifted “X” times, but not “X+l times”. For example, a 10RM is a weight that can be lifted 10 times, but not 11. One repetition maximum (IRM). The amount of weight that can be successfully lifted only once. Open chain exercises. Exercises where the terminal joint is free to move (Baechle & Earle, 2000). Parallel squat. A squat in which the top of the thigh is parallel to the ground during the lowest position of the squat (Figure 1). It is often determined at the point when the inguinal fold is at the same level as the superior aspect of the knee (Fry et al., 2003) Partial squat. Typically defined as squat lift in which the there is a 90 degree angle at the knee at the lowest position of the squat (Figure 4). For the purposes of this study, the depth was the same as for the box squat. Peripheral fatigue. Attenuation of the force response of contracting muscles due to factors in muscle activation that occur outside the central nervous system (Ni gg et al., 2000) Phasic muscle fibers. Another name for fast twitch muscle fibers. Powerlifting. Competitive weightlifting where maximal weights are lifted in the squat, deadlift, and bench press. 19 Rectification of EMG. Process of mathematically manipulating an EMG signal so that it may be quantified. Two methods may be used: (a) Full wave rectification-the negative EMG values are made positive. (b) Half wave rectification-the negative EMG values are removed from evaluation. Repetition (Rep). A single complete movement of an exercise (Fleck & Kraemer, 2004) Root mean squared. Method of quantifying amount of muscle activity in EMG signal. The formula for root mean squared evaluation is: 1 t+T 1/2 RMS(EMG(t) = (T f EMG2 (0dr) t Where (t) represents each moment of time, t represents the initial time, and T represents to total time evaluated (Robertson et al., 2004). Sets. A group of repetitions performed without rest (Fleck & Kraemer, 2004). Sets X reps. Common notation for a workout indicating both the number of sets performed and the number of repetitions in each set. For example, 3 X 10 would mean that three sets are to be performed and each set consists of 10 repetitions. Stretch shortening cycle. A muscle is eccentrically stretched followed immediately by a concentric contraction. The eccentric/concentric coupling causes a more powerful concentric contraction than if the concentric contraction was performed without the eccentric phase (Nigg et al., 2000). Training specifity. Theory that weight training movements should closely mimic competition movements to allow for the greatest adaptation (Baechle & Earle, 2000). 20 Tonic muscle fibers. Another name for slow twitch muscle fibers. Volume. Measure of total weight lifted during a training session. Volume is usually calculated by multiplying the number of sets times the number of repetitions times the weight used (Sets X Reps X Weight). However, volume has also been defined as the total number of repetitions performed. In this case, volume would be calculated by multiplying of the number of sets times the number of repetitions (Sets X Reps). Wingate cycle test. A test used to measure anaerobic endurance. Subjects perform a 30 second, maximal effort cycle test against a normalized resistance equal to .75 body weight. 21 CHAPTER 2 REVIEW OF LITERATURE The first section of this review will provide an overview of box squats and formal definitions of the weight training techniques (parallel, box, and partial squat) being addressed in this study. The proposed benefits and concerns associated with the use of these weight training techniques will also be discussed. Finally, possible dependent variables that could be used to assess these proposed benefits and concerns will be identified. The second section of this review will contain a discussion of the different analytical tools that are useful in the analysis of weight training techniques. The strengths and weaknesses of these devices shall be evaluated. During the course of this section, several studies pertaining to other “common beliefs” of strength training will be discussed to show their prevalence. These studies will also be reviewed to form a basis of what should be expected for other studies that incorporate these techniques. The final section of this review will be a synthesis of the methods to evaluate lifting and what should be evaluated in the particular case of the box squat. Reasons for choosing dependent and independent variables will be presented. 22 Overview of the Box Squat The Box Squat Weight training lore, like all forms of physical training and conditioning, is filled with long held traditions about the proper methods and techniques to cause improvement. Likewise, several new training methods and training devices are periodically introduced touting to produce superior physical development. Many of these techniques focus on isolating specific muscles or tout that greater muscle activity is produced. While some of these methods and devices have been tested scientifically, many are based on “common sense” and have anecdotal evidence for justification of their use. Several trends, such as the use of chains, bands, and stability training devices, have recently come into vogue with little scientific evidence validating the claims of the proponents who support their use (Ebben & Jensen, 2002; McBride, Cormie, & Deane, 2006). The use of box squats is also one of these non-validated training techniques. Squatting is one of the most used exercises for strength training of the lower extremities and lower back. There are many variations in technique and equipment used to perform squats. The most common form of squatting in strength training is the back squat, where a barbell is supported on the shoulders behind the neck (Figure 5). For the purposes of this paper, the term “squat” will imply that a version of the back squat is being performed. Individuals performing a squat start in an erect position and then allow the knees and hips to flex (i.e., “squat”) and then return to the erect starting position. The amount of flexion, particularly of the knees, can be used to describe different techniques of squatting. A squat where the top of the thighs are parallel to the floor at the point of greatest descent is known as a parallel squat (Figure 1). Likewise, a squat where 23 the posterior surface of the thighs come into contact with the posterior surface of the calves, restricting further knee flexion is known as a full squat. Finally, partial squats (Figure 4) are often defined as having a maximum knee flexion of 90 degrees, but any squat in which the anterior surfaces of the thighs do not descend below parallel to the surface of the floor is likely to be called a partial squat by weight training participants. Figure 5. Back squat starting position in which the barbell is supported behind the neck. 24 The box squat (Figure 2) is another variation of the squat. Several different techniques have been qualified as a box squat. The first method consists of the athlete descending in a controlled manner until the posterior surface of the thighs and buttocks come in contact with a box. The athlete does not sit on the box. Instead, the athlete immediately starts the ascent (concentric portion of the lift) following contact with the box. This same method can be used with any restraint (e. g., chairs, benches) positioned to come into contact with the thighs or buttocks. The second method of box squatting consists of the athlete descending onto and sitting on the restraint before returning to a standing position. In this method, the act of sitting separates the eccentric and concentric portions Of the lift. There is a time of partial unloading of the muscles of the lower extremity, and the stretch-shortening cycle is interrupted due to the pause on the restraint. The box squat method that will be studied in this research is this second method. There are two notable proponents of the use of box squats: Louie Simmons and Bigger Faster Stronger (BF S). Louie Simmons is a recognized expert in powerlifting, having authored several papers on training, created several training videos, and consulted for the Cleveland Browns, Green Bay Packers, Seattle Seahawks, and New England Patriots of the National Football League (Simmons, 2006). Bigger Faster Stronger is an organization that provides strength training education to participants in high school and small college athletic programs across America in the form of workout programs, clinics, and certification programs for coaches (Shepard, 2004b, 2004d). Promotional literature for BFS states that over 9,000 high schools have implemented their strength training program and lists professional teams, such as the Green Bay Packers of the National 25 Football League and Utah Jazz of the National Basketball Association, as teams that they consult (Shepard, 2004b). Although both Mr. Simmons and BF S promote the use of box squats, their method of performance of the box squat is different. In Mr. Simmons’ method, a box that will allow the athlete to sit with his/her anterior surfaces of the thighs at a level that is slightly lower than parallel to ground is used and a weight lower than what is normally used during a parallel squat workout (approximately 60%) is employed. Athletes descend in a controlled manner, sit on the box, and pause for a brief period of time (approximately a second) and return to their standing position. In contrast, The BF S box squat technique consists of athletes descending onto a box that is high enough to put them into a position with the thighs slightly (5 cm) above parallel and using more weight (50- 150 pounds) than what is normally used in a parallel squat workout (Shepard, 2004a, 2004c, 2004d). Athletes can use more weight because the squats are performed above parallel and possibly because of the reduced isometric force needed during the transition from the eccentric descent to concentric ascent portion of the lift. The BFS program suggests that no more than 100 to 150 additional pounds should be used when box squatting compared to what is normally used during a parallel squat workout (Shepard, 2004a, 2004c, 2004d). The BFS program has also promoted slight variations of their method of box squatting. Currently, athletes are encouraged to finish the lift with a plantar flexion of the ankles or “toe raise.” This is supposed to simulate the explosive movement an athlete would perform during a sporting movement such as a sprint start (Shepard 2004a). However, BFS has also taught the box squat without the ankle plantar flexion at the end 26 of the ascent and so there is variation in the performance of the box squat depending on how it was implemented. It is the author’s opinion that the BF S literature is more readily available than Mr. Simmons’ literature for the average high school coach. Because the main intent of this study was to evaluate the effectiveness of the BF S method of box squat as used by high school athletes, the rest of this literature review will be directed to the technique taught by the BFS program. There is some concern about the use of box squats and possible injury to the lower back. This has been the topic of discussion for two point/counterpoint articles in the Strength and Conditioning Journal (Brown, 1998 & 2003). These arguments have only provided anecdotal evidence for and against possible injurious effects of box squats on the lower back. One author stated that a study showed that there were more hemiations and disc compressions in football players who performed box squats compared to those who only performed regular squats (Brown, 2003). However, the study was not formally cited and could not be found using publication search engines. BF S does address this concern in their literature; however, they only present anecdotal evidence to the safety of the lift. BFS states that no one has been injured performing box squats in over 3,000 clinics (Shepard, 2004a). Likewise, they have published an article where an orthopedic surgeon states that there are no dangers in performing box squats (Goss, 2005). However, no study was performed or published. The surgeon makes this statement after only performing the exercise himself. These methods of support placate the average reader and provide authoritative proof to the users of the program. 27 Bigger Faster Stronger provides several reasons why they choose to perform box squats. Box squats are believed to be easier to teach to a beginning weight trainer than a regular parallel squat (Shepard, 2004b). Also, the concept of training specificity is cited as a reason to perform the box squat. Athletic training specificity is the belief that strength training methods are better when they closely mimic the same actions that athletes are called upon to perform in their sports settings. The pause in the middle of the lift removes the stretch shortening cycle component of the lift. This would mimic the movement that occurs from a static start position such as a track sprint start and a football lineman exploding out of a stance. Box squats are believed to develop greater “hip strength” than parallel squats (Shepard, 2004a). Additionally, it is believed that box squats allow for faster recovery of the legs after a workout (Shepard, 2004a). Only anecdotal evidence is available to support these claims. For example, BFS does not specify which muscles they are referring to when they talk about greater “hip” development from performing box squats and data supporting/refuting this claim is limited. Other statements allude to the notion that the amount of gluteal involvement is greater in box squats compared to parallel squats. This statement appears to be contradictory to research studies that have been performed on back squats, but without actual analysis of the box squat, it cannot be confirmed or contradicted (Caterisano et al., 2002). Probably the most perplexing statement is that box squats allow for faster recovery of the legs after a workout. It is believed that because of this faster recovery, 3 weight training program which includes box squats can be used by athletes the day before their athletic contest and not adversely affect athletic performance during the contest 28 (Shepard, 2004a, 2004c). What is meant by faster recovery is not well defined in the BFS literature. Anecdotal evidence is provided where an athlete is tested for maximum vertical jump height prior to a set of box squats. The athlete then performs one set of box squats and, after approximately an hour, the maximum vertical jump is retested. The performance is equivocal at the post-test. Shepard (2004c) believes that this would not be possible after a set a parallel squats, but it is not mentioned whether a subject has ever been tested in this manner. The type of fatigue that is created due to performing either the box or the parallel squat has not been completely explored. The acute neuromuscular fatigue that occurs due to weight training can be due to decreased neural activity (central fatigue) or due to decreased force production of the muscles (peripheral fatigue) (Woolstenhulme, et al., 2004). Neither of these types of fatigue are addressed in any of the literature that was found on box squats. Although box squats have not been analyzed, analysis of other squatting methods allow for some conjecture of the BFS claims. Many different dependent variables have been used in these studies. The dependent variables that were addressed in the current study are: (a) muscle activity, (b) joint forces and moments, (c) perceived exertion, and ((1) evaluation on performance tests after bouts of weight training exercises. In the current study, the independent variables were the different methods of squatting (parallel, box, and partial). The differences in these methods that have been analyzed in previous studies are the depth of descent and the amount of weight used to perform the exercise. What had not been analyzed was what changes occur when there is an unloading of the lower extremities during the transition from the eccentric to concentric phases of the squat associated with sitting on a box or other restraint at the lowest point of the descent. 29 There were two primary issues that needed to be addressed. The first was the concern over the safety of performing box squats. The second was what has been learned about the dependent variables of interest from previous studies of squatting and what can possibly be learned by analyzing these dependent variables with respect to the three different types of squats of interest (parallel, box, partial). In the following sections, there will first be a discussion of safety concerns associated with box squats and then a summary analysis of the different dependent variables. Strengths and weaknesses of each analysis method will be addressed. Finally, a summary of what was expected from this study and what will still be unanswered will be discussed. Safety Concerns of Strength Training and the Box Squat Although weight training is used as a means of improving sports performance, there is great concern over the possible negative effects due to the heavy loads imposed on the body. As mentioned previously, there is a concern about the use of box squats and possible injury to the lower back. However, no known studies have evaluated the safety of the box squat. Assumptions may be made from studies that have evaluated other weight training techniques, in particular the back squat and the deadlift. The deadlift is a lifting technique similar to the squat; however, instead of the barbell being supported on the shoulders behind the neck, the barbell is held in the hands in front of the body. Additionally, the deadlift only has a concentric phase, while the squat has both eccentric and concentric phases. The deadlift develops the posterior trunk muscles to a greater extent than the squat (Escamilla, Lander, & Garhammer, 2000). Before analyzing what has been learned about strength training and the stresses on the back, a review of spinal anatomy may be beneficial. The spinal column consists of 24 30 articulating vertebrae and nine fused vertebrae (Anderson & McNeil, 1989). Of these vertebrae, the lumbar are the most studied due to the concern of possible injury from the forces and moments that are placed on the lumbar region during lifting. The lumbar vertebrae are the most inferior, mobile vertebrae, and range in number between four and six (Goel & Weinstein, 1990). Additionally, there are four main curvatures of the spine. The cervical and lumbar regions are in lordosis (convex forward) and the thoracic and sacral regions are kyphosis (convex backward) (Saladin, 2001). Normal curvatures of the spine should be maintained during lifting techniques such as the squat and deadlift. (McGill, 2002; Siff, 2003). The main reason for trying to maintain these curvatures is that injury is more likely if the spine is placed in extreme flexion or extension. In reality, flexion of the spine will occur during both the squat and the deadlift, and this flexion may allow the spine to better handle the compressive forces exerted on it, as long as complete flexion of the spine does not occur (Adams & Hutton, 1985; McGill, 2002). Injuries may occur to the invertebral discs or to the vertebral bodies. The injuring of the discs occurs most often when the spine is both in flexion and compression (Hamill & Knutzen, 1995). Conversely, when there is compression without flexion/extension, it is more likely that the vertebral body will break before the disc will rupture (Hamill & Knutzen, 1995). Both the squat and deadlift have been analyzed to estimate the stresses placed on the lumbar spine. Because of the invasive nature of measuring actual intradisc pressure, models have been used to determine the compressive forces and moments on the spine. These models have revealed that the loads experienced by the lower back are significant in magnitude. For example, Cholewicki, McGil and Norman (1991) reported that in the 31 deadlift forces on the spine could be in excess of 10 times body weight. Likewise, Cappozzo, Felici, Figura, and Gazzani (1985) reported that the compressive load acting on the L3-L4 joint during a half squat exercise ranged between 6-10 times body weight for their four participants. Granhed, Jonson, and Hansson (1987) measured the compressive load created on the L3 joint in eight Swedish powerlifters. The peak compressive loads were reported to be between 18,800 and 36,400 N. Surprisingly, these values were greater than the calculated maximal in vitro forces for failure of the vertebral bodies (Hansson, Roos, & Nachmeson, 1981). One reason for the discrepancy between these reported experienced values and the maximal forces before failure is the complexity of modeling the forces acting on the spine. Multiple muscles with various directions of pull, intraabdominal pressure, and intrathoracic pressure must all be taken into account when modeling spinal forces. In most cases, models are created by reduction or optimization methods. Accurately measuring these forces increases the invasiveness of the measurement and are still only an approximation of the actual forces. For example, Lander, Simonton, and Giacobbe (1990) and Lander, Bates, and Devita (1986) measured intraabdominal pressure by insertion of a balloon catheter 5 cm into the rectum of their participants. While this method increases the accuracy of the model, it may limit the number of people willing to participate in such an experiment. Although the aforementioned studies may cause concerns about the use of squats and deadlifts, further studies by Cholewicki and McGill have not shown injury when using these methods unless firll flexion of the spine occurs (McGill, 2002). 32 Box squats further complicate these concerns about stresses produced on the lower back due to the fact the athlete sits down completely on a box and allows for some unloading of the lower extremity. The previously discussed studies have not addressed how the pressures exerted on the spine would change if a person were to sit down and unload the lower extremities. Furthermore, no known studies have evaluated and compared stresses on the spine for both a seated and loaded condition. However, several studies have evaluated the stresses on the spine in an unloaded condition. For example, Nachemson and Morris (1964) observed that, in vivo, lumbar disc pressure was 35% greater while sitting without lumbar back support than when standing. These findings were supported by the Andersson et al. (1974a, b, c, (1) series of seated studies. Andersson et al. (1974a) evaluated both EMG and intradisc pressure at the third lumbar disc. Four participants were evaluated in the following conditions: standing, sitting relaxed, sitting relaxed with arm support, sitting relaxed with feet unsupported, sitting straight up, sitting with an anterior lean, and sitting with a posterior lean. Intradisc pressure was evaluated by insertion of a piezoresitive needle between the third and fourth vertebrae and another needle into the psoas muscle. Electrodes were placed 3 cm lateral on both sides of the spine at the C4, T5, and L1 levels. Additionally, electrodes were also placed on the left side of the spine at the T8, T10, and L3 levels for two of the participants. After preparation, participants were seated in the previously mentioned positions, both with and without support for the lower back. Unsupported sitting had higher intradisc pressure compared to regular standing. Andersson et al. (1974a) suggested that the primary reason for the increase in pressure was due to the change in spinal curvature with sitting. Chaffin, Anderson, and Martin (1999) have 33 stated that intradisc pressure is greater in the seated position as long as there is no support, such as a back rest for the lumbar region of the spine. The back rest would help maintain the curvatures of the spine found in normal standing. From these findings, it is reasonable to assume that there is an increase in intradisc pressure while sitting during the box squat. Technique suggestions, provided by Shepard (2004a), of “keeping the back tight” (i.e., attempting to maintain normal curvature of the spine) and “not dropping hard onto the box” would minimize these increased pressures, but there would still be an increase because there would be some change in the spinal curvature due to sitting. However, it cannot be determined if the increase is enough to cause damage to either the vertebrae or the invertebral discs. Actual measurements of these changes would be extremely invasive and models of the pressures would suffer from the problems mentioned in previous studies. Therefore, although the question of whether or not box squats are dangerous to the spine is of utmost importance, it may be more realistic to address the question of whether or not there is a different rate of recovery from a box squat workout compared to a parallel squat workout and if there is a difference in muscle activity between the two lifts. Determination of whether to use box squats could then be made on basis of comparison of benefits to possible dangers. Analysis of Weight Training Technique EM G Evaluation EMG is a means of measuring muscle activity. For a muscle to contract, it must receive a signal from its corresponding motor neurons. A motor neuron and all of the muscle fibers it innervates is known as a motor unit. The number of muscle fibers 34 innervated by a motor neuron is dependent upon the function of the muscle. No matter the size the motor unit, it is the chemical release of acetylcholine, the neurotransmitter responsible for muscle contraction, from the motor neuron at the neuromuscular junction that causes changes in the permeability of the muscle membrane and ultimately, a change in electrical potential. This change in electrical potential then propagates the length of the muscle fiber, causing the fiber to contract. It is this propagation of the change in electrical potential that is recorded by EMG. EMG can be a useful tool to determine whether an exercise is recruiting the desired muscles. The raw EMG signal only allows for an understanding of when a muscle is active. This information can be beneficial in understanding the sequencing of muscle actions and also whether an activity incorporates the muscle in question. For example, Sands (2004) showed that a commonly used exercise to train gymnasts for the iron cross position on the rings did not recruit the same muscles as the actual iron cross activity. This type of evaluation would be the most ideal use of EMG because it evaluated only whether the muscles were active and did not interpret the level of activity of the muscles. The magnitude (amplitude) of the EMG signal gives some indication about the relative amount of muscle recruited to perform an activity, but many factors contribute to the interpretation of the amplitude of the signal. The change in amplitude of an EMG signal can be due to an increased rate at which a motor unit is recruited, increased number of motor units being recruited, and/or synchronization of the motor units. Motor units are recruited by the size principle (Winter, 1990). Smaller motor units that are more resistant to fatigue and that create smaller action potential are recruited first. As more 35 force is required to perform an activity, these fibers are stimulated more frequently to maintain a contraction. Likewise, other motor units can be recruited as the need for force increases. When multiple motor units are recruited, the action potentials of these motor units that are recorded by EMG are summated into a single wave. Unfortunately, unless fine wire EMG, which can be used to monitor smaller muscles or even single motor units, is used, determination of which of these factors is causing the change in amplitude is impossible. Several other factors contribute to the amplitude of the recorded EMG signal, which further complicates the evaluation of muscle activity. Skin, connective tissue, other muscles, and even blood flow can reduce the amplitude of the recorded signal. Likewise, the location of the electrodes on or in a muscle will change the recorded amplitude. Therefore, if a motor unit that is close to the electrode, or that has minimal tissue between it and the electrode, is recruited, the signal recorded will have a larger amplitude than a same size motor unit that is recruited farther away from the electrode. Thus, although larger recorded EMG amplitudes often imply that more effort was required to perform a movement, EMG signals cannot be directly compared between individuals. Results should only be interpreted to the individual being studied and in comparison to other movements that were performed in that testing session in which the position of the electrodes were not changed. Another factor is the interpretation of the EMG signal changes during a dynamic movement. The amplitude and frequency of the signal is dependent upon muscle length and position on the muscle, both of which are constantly changing during a dynamic movement (Robertson et al., 2004). Ideally, 36 evaluation should occur in an isometric condition, such as the aforementioned evaluation of the iron cross by Sands (2004). Even with the difficulties of interpreting the EMG signal, a preferred use is to quantify the amount of relative muscle exertion in an activity. The raw EMG signal must be modified for this to occur. The action potentials create sinusoidal waves that, when averaged over time, would equal zero due to equivalent positive and negative portions of the wave. One of the most common means of modifying the signal is to rectify it. EMG recordings can be modified so that the negative signal is either converted to positive value (full wave rectification) or is removed (half wave rectification). Full wave rectification is the preferred method of modification as it maintains the entire EMG signal. The signal can then subsequently be evaluated by several methods. Once the signal has been rectified, there are multiple calculations that can be performed to interpret the signal. The most common interpretation method is integration which involves calculating area under the EMG signal as volt seconds. This is done by integrating for either a set amount of time and defining the time units, or by integrating until a set amount of “energy” is reached prior to re-setting. A method close to integration is the use of a “linear envelope.” In this method, a low pass filter is applied to the EMG signal and the resulting wave is a representation of the average EMG signal at any given moment (Winter, 1990). A third method that is used to estimate average muscle activity, that does not involve rectification of the signal, is the root mean squared amplitude. The root mean squared (RMS) amplitude is calculated by the use of the following formula: 37 1 t+T 1/2 RMS(EMG(t) = (T I EMG2 (0dr) Where (t) represents each moment of time, t represents the initial time, and T represents to total time evaluated (Robertson et al., 2004). The electrical activity of a muscle during different movements may be quantitatively compared by the use of any of these methods. Interpretation of EMG signals is difficult due to the dynamic nature of the movements. Muscle contractions are often evaluated isometrically and the resulting EMG analysis is then assumed to reflect what would occur in a dynamic movement. However, this will not allow for interpretation of the muscle activity over the whole range of movement and does not represent how the activity will be used in training. A second method to limit the amount of variability in the signal due to movement is the use isokinetic machines. These machines keep the velocity of movement constant, yet still permit the performance of the movement through the full range of motion. This method also is not a completely ideal answer. Isokinetic dynarnometers are limited in the number of movements that can be evaluated. Moreover, the controlling of the rate of movement does not necessarily control for the rate change in length of the muscle. A third method is to perform the activity under a guided tempo. This method does not restrict movement due to having to use a machine and thus may be more realistic to what occurs normally. However, changing the temporal movement may not be representative of how the activity is performed in a “normal” setting. Additionally, participants may not comply with the guided tempo. 38 Thus, it should be evident that, although EMG can be useful in describing the activity of muscle, more caution is needed when trying to interpret the EMG signal activity in terms of exertion. All efforts should be made to regulate the movement during a study. Additionally, comparison of studies should only be performed between studies that used similar methods of regulation and recording. EMG has been used to evaluate several common training techniques of strength training. Most of these techniques are based on assumptions of how changing the position of the body or the means of performing an exercise will affect muscle recruitment. Several commonly held training beliefs have been supported or refirted using EMG. The majority of these studies have been performed on the upper body and in particular, on the bench press. For example, Barnett et al. (1995) observed that pectoralis major recruitment was greatest with a narrow grip and the use of decline and incline presses did not significantly increase upper and lower pectoralis muscle recruitment. The rate of movement in this study was not directly controlled, but had been practiced at a rate of approximately two seconds (one second eccentric, one second concentric) to complete the lift and was then monitored during the lifting to verify it was consistent. Likewise, Glass and Armstrong (1997) observed that the upper pectoral muscle was not less engaged in the performance of a decline press when compared to an incline press. This was also a dynamic evaluation, but, unlike the previous study, the rate of movement was set at three seconds (1.5 seconds eccentric, 1.5 seconds concentric) and was regulated by metronome. Many bodybuilding books advocate the use of regular, incline, and decline presses to develop the middle, upper, and lower portions of the chest, 39 respectively. However, these studies suggest that these different lifts may not be as beneficial to specialized development as previously thought. Another suggested technique is to increase hand width during bench pressing or push-up exercises to increase pectoralis involvement. However, Cogely et a1. (2005) observed that pectoralis recruitment was greater with a narrow hand placement during a push-up. A standard cadence of three seconds for the concentric portion of the lift was used and only the concentric portion was evaluated. Furthermore, Barnett et al. (1995) was not able to show increased pectoralis recruitment with an increase in grip width for the bench press. However, Clemons and Aaron (1997) observed that there was an increase in pectoralis recruitment with increasing width of grip while performing the bench press. Rate was not controlled in this experiment, but was monitored by videography. To try to explain the discrepancies in the above studies, Lehman (2005) evaluated changes in chest and upper arm muscles using isometric contractions. Greater EMG activity was observed in the triceps with a narrower grip, but, in contrast to the studies of Cogely et a1. (2005) and Barnett et a1. (1995), Lehman did observe lower pectoralis activity with a narrower grip. Other training suggestions for upper body lifts have been evaluated. McCaw and Friday (1994) found support for the concept that weight training with free weights requires more muscle activation than training with machines. A six second (three second eccentric, three second concentric) movement was used for both the machine and the barbell bench press. Signorile et a1. (2002) observed that muscle recruitment was different for different grips in the lat pull-down exercise. In particular, the latissimus dorsi was most activated during a wide grip performance of the exercise. Movement was 40 controlled so that both eccentric and concentric movements each occurred in two seconds. EMG studies of the lower body have also been performed, but the methods used to evaluate the EMG signal with the lower body have been more variable than for the upper body. Table 1 includes a summary of several studies of the EMG activity during squatting exercises. Many of these studies have not accounted for the rate of movement during the squatting exercise even though it has been shown that the rate of movement affects the recorded EMG signal (Robertson et al., 2004; Winter, 1990). Even those that have controlled for the timing have not always kept it completely consistent. Escamilla et a1. (1998) and Esarnilla et a1. (2001) encouraged a consistent movement in which the eccentric phase was between 1.5 and 2 seconds while the concentric phase was between 1 and 1.5 seconds. The muscles that have been evaluated have varied across many of the studies. Many studies have evaluated two or more of the quadriceps muscles (e. g., rectus femoris, vastus lateralis, vastus medialis) and have shown similar behavior for these muscles across different conditions. However, there is often greater activity for the vastus muscles compared to the rectus femoris (Bosco et al., 2000; Escamilla et al., 1998; Isear et al., 1997; Wretenberg et al., 1993, 1996). Part of the reason for the different results is due to differences in what aspects of the lift were being evaluated. Some of the studies were only interested in the activity of the quadriceps (Signorile et al. 1994, 1995), while others were also interested in the activity of the antagonists, such as the harnstrings and gastrocnemius, during the lift (Ebben & Jensen, 2002; Escamilla et al. 1998; Caterisano et al., 2004; Wretenberg et al., 1993, 1996). 41 Table 1 Summafl of EMG Evaluations of Squatting Exercises Author Participants Muscles Movement Method of Evaluation (Date) Evaluated* Regulation” in seconds (s) Wretenberg 8 male VM, VL, Not specified Averaged, full wave et a1. (1993) national BF rectified, low pass weightlifters filtered, and normalized to reference lift Signorile et 10 males VM, VL Not specified RMS*** for the duration a1. (1994) of the entire lift Signorile et 10 males VM, VL, ECC: 2 3 Average RMS a1. (1995) RF CON: 2 s normalized to the highest average RMS recorded Wilk et a1. 10 males VM, VL, Not specified Normalized to (1996) RF, LH, MVIC**** MH, G Wretenberg 8 male VM, VL, Not specified Averaged, fiill wave et a1. (1996) weightlifters BF rectified, low pass 6 male filtered, and normalized powerlifters to reference lift Isear et a1. 20 males GM, VM, Metronome: RMS EMG signal (1997) 21 females RF, VL, G, ECC: 1.2 s normalized to MVICs of H Pause: 1.2 3 each muscle CON: 1.2 s * VM = vastus medialis, VL = vastus lateralis, RF = rectus femoris, GM = gluteus maximus, G = gastrocnemius, BF = biceps femoris, MH = medial hamstrings, H = hamstrings, Q = quadriceps. ** ECC = eccentric, CON = concentric. ***RMS= root mean squared. ****MVIC=maximal voluntary isometric contractions. 42 Table l Continued Author Participants Muscles Movement Method of Evaluation (Date) Evaluated* Regulation“ in seconds (3) Ninos et al. 14 males VM, VL, Metronome RMS*** EMG signal (1997) 11 females BF, MH, ECC: 2 s normalized to CON: 2 s MVICs**** of each muscle Escamilla et 10 males RF, VM, Slow continuous Normalized to MVIC a1. (1998) VL, BF, manner (approx. MH, G 1.5-25 for ECC, 1-1.5 s for CON) but not controlled Bosco et a1. 6 male RF, VL, Not specified RMS (2000) sprinters VM 6 female sprinters 6 male bodybuilders Escamilla et 10 males RF, VM, Slow continuous Normalized to MVIC a1. (2001) VL, BF, manner (approx. MH, G 1.5-28 for ECC, 1-1.5 s for CON) but not controlled * VM = vastus medialis, VL = vastus lateralis, RF = rectus femoris, GM = gluteus maximus, G = gastrocnemius, BF = biceps femoris, MH = medial hamstrings, H = hamstrings, Q = quadriceps. ** ECC = eccentric, CON = concentric. ***RMS= root mean squared. ****MVICmuimal voluntary isometric contractions. 43 Table 1 Continued Author Participants Muscles Movement Method of Evaluation (Date) Evaluated* Regulation** in seconds (5) Caterisano et 10 males VL, VM, Not specified Peak and mean al. (2002) BF, GM integrated EMG normalized to total EMG activity of the 4 muscles Ebben and 5 males Q, H Not specified Mean full wave Jensen 6 females rectified integrated- (2002) EMG * VM = vastus medialis, VL = vastus lateralis, RF = rectus femoris, GM = gluteus maximus, G = gastrocnemius, BF = biceps femoris, MH = medial hamstrings, H = hamstrings, Q = quadriceps. ** ECC = eccentric, CON = concentric. ***RMS= root mean squared. ****MVIC=maximal voluntary isometric contractions. Finally, the methods used to interpret the EMG also varied greatly. From these studies it is difficult to find a consensus as to what would be the proper method of EMG use. This difficulty stems from the underlying problem that the method used may vary depending on what particular questions need to be answered. These studies also have evaluated common training suggestions and, as with the upper body, varying amounts of support were found. In squat lifts, Signorile et a1. (1995) did not find significantly different EMG activity in the different muscles of the quadriceps for different alignments of the feet on the ground. It is commonly taught that different orientations of the feet during the squat results in different development of the 44 muscles of the quadriceps (e. g., turning the feet outward will develop the vastus medialis to greater extent). Likewise, Ebben and Jensen (2002) did not find any statistical difference in quadriceps or hamstring EMG activity when squats were performed using bands or chains in addition to the regular weight. The use of bands and chains has become popular in performing squats to allow athletes to have less weight on the bar (i.e., a portion of the chain is supported by the ground) when they are in the lowest squat position, where they are the weakest, and an increasing amount of weight as they ascend back to the starting position. Finally, Escamilla et a1. (2001) found no difference in quadriceps activity from using a wide stance compared to a narrow stance. However, slight differences were found in hamstrings activity, suggesting that a change in stance may be precipitate a change in the recruitment of the hamstring muscles. Depth of squatting is a highly studied topic because of the concern for potential damage to the knees with full squats. Wretenberg et a1. (1993) reported that quadriceps activity was greater in a parallel and deep squat compared to a partial squat. However, the amount of EMG activity was not significantly different between the parallel squat and the deep squat. From these findings, Wretenberg et al. (1993) suggested that a parallel squat may be as beneficial for quadriceps development as a full squat and parallel squats may have less potential for causing knee damage since they did not create as great of moment at the knee. Caterisano et a1. (2002) evaluated the commonly taught belief that hamstring activity increases with depth of squat. Ten male lifters were evaluated in their performance of three different depths of squats. EMG of the vastus lateralis, vastus medialis, biceps femoris, and gluteus maximus were recorded. The integrated EMG was 45 then summed for the four muscles to create a “total muscle activity” value. The mean integrated muscle activity of each individual muscle was normalized to the total muscle activity. The biceps femoris did not have greater activity with greater depth, but there was greater muscle activity in the gluteus maximus with increasing depth. Although the focus of the study was not squat depth, Bosco et al. (2000) reported that EMG activity of the quadriceps, evaluated using RMS, decreased during a bout of half squats, but did not decrease during a bout of parallel squats when compared to initial values. Bosco et a1. (2000) suggested that a possible reason for this observation could be that the half squats initially recruited phasic muscle fibers and as the set progressed, tonic fibers, which have smaller action potentials, were more highly recruited to perform the work. Likewise, it was suggested that the parallel squats recruited primarily the tonic muscle fibers and that peripheral fatigue of the muscle caused the decrease in power output since the EMG activity did not change. EMG has also been used to help model the forces experienced at the knee during squatting. Escamilla et al. (1998) evaluated the stresses upon the knee during open chain (leg extension) and closed chain (squat and leg press) exercises using EMG, force transducers, and videography. Ten experienced weightlifters were evaluated in this experiment. EMG analysis was evaluated for the vastus lateralis, rectus femoris, vastus medialis, biceps femoris, medial hamstrings, and gastrocnemius. Rate of movement was monitored, but was not completely regulated. It was estimated that both the concentric and eccentric actions each occurred in 1.5-2.0 seconds. Rest time between exercises was chosen by the participants. EMG was rectified and then averaged using a .01 s moving window. The data were then normalized to maximal voluntary isometric contractions 46 (MVIC) that had been performed prior to the exercises. The MVICs for the quadriceps and hamstring muscles were performed on a seated leg extension machine with the knee at 90 degrees of flexion. Three trials of three seconds occurred for each MVIC. This normalized data were then used to calculate the forces exerted by the quadriceps in Escamilla et al.’s (1998) model of the knee. Kinematic and Kinetic Analysis The use of kinematic evaluation has led to a greater understanding of lifting technique. Table 2 includes summaries of several studies that have used kinematic analysis to evaluate squatting or deadlifting techniques. Methods reported in the literature have varied greatly. Analysis of film (Andrews Hay, & Vaughn, 1983; Brown & Abani, 1985; Lander et al., 1986; Lander et al. 1990; McLaughlin et al. 1977, 1978; Russell & Phillips, 1989) has been the primary means of evaluation; however, as technology has progressed, the use of videography and infrared cameras has replaced the use of film. This change is due to the easier evaluation of digital data from video or infrared images in comparison to the need to physically digitize film images prior to subsequent computer analysis. Evaluation of these summaries reveals that there have not been any established standards to analyzing and evaluating squatting techniques. Most studies of the squat have used a three or four segment model of the lifter. However, Russell and Phillips (1989) chose to use a five segment model when comparing the back squat to the front squat to allow for evaluation of the stresses placed on the lower back region. Their methods were drawn into question by Fry et al. (1993) because the end of the bar was used to represent the shoulder for all lifts. Fry et al. demonstrated that using the end of 47 the bar to represent the shoulder in the front squat significantly changes the calculated angle of the trunk when compared to using a fixed landmark on the body such as the seventh cervical vertebrae. These studies show that it is important to state and define what landmarks are being used for the model. The methods of analyzing the kinematic and kinetic data has also varied greatly. Some studies only used kinematic data and then calculated the kinetic parameters using inverse dynamics (Andrews et al., 1983; Brown & Abani, 1985; Lander et al., 1986; Lander et al. 1990; McLaughlin et al., 1977, 1978; Russell & Phillips, 1989). Others combined kinematic data with ground reaction forces measured via force platform (Lander et al. 1986, 1990; Wretenberg et al., 1993, 1996). The most common evaluation of kinetic stresses on the body has been done using static or “quasi-static”, otherwise known as “semi—dynamic”, methods. In a quasi-static evaluation, ground reaction forces are incorporated into the model calculation of forces at the joints; however, limb translational and angular accelerations are considered minimal and are not included. Several studies have compared data from both static or semi-dynamic evaluation and true inverse dynamic evaluation. McLaughlin et al. (1978) stated that their static evaluation of data was within 10% of the dynamic evaluation. Lander et al. (1990) found a 1% difference between their quasi static evaluation and hill dynamic evaluation of a squat lift. Lindbeck and Arborelius (1991) observed a 3% difference between the two methods of calculation. These studies suggest that the use of semi-dynamic methods of evaluating forces and moments at the joints during squatting exercises are justifiable when compared to the extra time and effort needed to perform true dynamic evaluation. 48 Kinetic evaluation has been primarily used to assess the forces and moments experienced at the knees and hips. McLaughlin et al. (1978) observed that higher skilled powerlifters created lower trunk moments by maintaining a more erect posture during squatting. This observation was obtained from twelve national powerlifters, divided into highly skilled (n=8) and less skilled (n=4) groups, who were evaluated from a sagittal view during a powerlifting competition. From this study, recommendations have been made to maintain a small trunk angle and to limit the amount of excursion of the knee over the feet (Chandler & Stone, 1991). 49 Table 2 Summary of Kinematic Evaluations oquuatting Author Kinematic Method of (Date) Participants Model Method Evaluation Squat Studies McLaughlin, 24 senior 3 segment Locam 2-D Kinematic Dillman, & AAU (shank, thigh, 16 mm Film evaluation of bar Lardner competitors trunk) 96.3-97.6 fps* and limb movement (1977) (gender not specified) McLaughlin, 12 senior 3 segment Locam 2-D Inverse Lardner, & AAU (shank, thigh, 16 mm Film dynamics and static Dillman competitors trunk) 96.3-97.6 fps evaluation divided (1978) (gender not into 6 phases specified) Andrews, 3 males 4 segment Locam 2-D Inverse Hay, & (foot, shank, 16 mm Film dynamics Vaughn thigh, trunk) 50 fps (1983) Cappozzo et 2 males and 5 segment COSTEL 2-D Inverse al. 2 females (foot, shank, Optoelectric dynamics (1985) thigh, pelvis, Infrared trunk) Camera Lander, Bates, 6 experienced 4 segment Locam 2-D Semi-dynamic & Devita males (foot, shank, 16mm Film evaluation (1986) thigh, trunk) 50 fps lift divided into 6 and force phases plate Hattin, 10 males 4 segment 3 Infrared 3-D Inverse Pierrynowski, (foot, shank, cameras dynamics & Ball thigh, pelvis) 50 Hz** (1989) *fps=frames per second. ** Hz=sample rate in samples per second. 50 Table 2 Continued Author Kinematic Method of (Date) Participants Model Method Evaluation Squat Studies Russell & 8 college 5 segment 2-D Inverse Phillips males (foot, shank, 16mm Film dynamics (1989) thigh, 50 fps* pelvis, trunk) Lander, 6 males 4 segment Locam 2-D Semi-dynamic Simonton, & (foot, shank, 16mm Film evaluation Giacobbe thigh, trunk) 40 fps lift divided into 6 (1990) and force phases plate Lindbeck & 10 males 6 segment (foot, Inflated 2-D Semi-dynamic Arborelius shank, thigh, cameras and dynamic (1991) head and trunk, 200 Hz** arm, forearm) Fry, Aro, 6 males 5 segment Digital video- 2-D Static Bauer, & (foot, shank, taken at 60 evaluation at lowest Kraemer thigh, Hz, analayzed position (1993) pelvis, trunk) at 20 Hz Wretenberg, 8 male 3 segment (foot, Video camera 2-D Semi-dynamic Feng, Linberg, national shank, thigh) 25 Hz & Arborelius weightlifters (1993) Wretenberg, 8 male 3 segment (foot, Video camera 2-D Semi-dynamic Feng, & national shank, thigh) 25 Hz Arborelius weightlifters (1996) 6 male national powerlifters *fps=frames per second. **Hz=sample rate in samples per second. 51 Table 2 Continued Author Kinematic Method of (Date) Participants Model Method Evaluation Sguat Studies Escamilla et 10 males 2 segment (foot Four charged 3-D Inverse al. (1998) and shank) couple device dynamic with force cameras plate and EMG data 60 Hz** Escamilla et 10 males 2 segment (foot Four charged 3-D Inverse al. (2001) and shank) couple device dynamic with force cameras plate and EMG data 60 Hz Fry, Smith, 7 trained 4 segment Video camera 2-D Static & Schilling males (foot, shank, (rate not evaluation at lowest (2003) thigh, trunk) stated) position Deadlift Studies Brown & 21 teenage 6 segment Locam 2-D Inverse Abani (1985) males (shank, thigh, 16 mm Film dynamics trunk, head, arm, 40 fps forearm) McGuigan & 29 elite 6 segment Video camera Kinematic analysis Wilson powerlifters (shank, thigh, 50 Hz of angles and (1996) trunk, head, arm, velocities of body forearm) segments and the bar Escamilla et 39 male 15 point spatial Two 3-D and 2-D al. (2000) master level model synchronized Inverse dynamic powerlifters video cameras 60 Hz **Hz=sample rate in samples per second. Fry, Smith, and Schilling (2003) have debated the suggestion to limit the excursion of the knees over the feet. Fry et al. studied seven men performing the back squat exercise in two different methods. The first was a parallel squat with no restrictions that allowed the knees to extend over the toes as the participants descended. The second was a squat where the knees were not allowed to extend over the toes (by placing a barrier in front of the knees) and requiring the same depth as the first parallel squat. The participants were videotaped in a sagittal view and the reactive forces and moments were calculated at the lowest position of the squat in two different situations. A two dimensional static model was used to evaluate the torques experienced at the hip and knees during the back squat. Fry et al.’s (2003) evaluation supported McLaughlin et al.’s (1978) findings of lower knee moments with less knee excursion, but the authors argued that the reduced knee stress resulted in increased stress to the hips and lower back and thus the recommendation to not allow knee excursion over the toes may be too strict. While excessive motion of the knees in front of the feet is not recommended, it may be more beneficial to allow some latitude to reduce the stresses experienced in the hips and lower back. Knee and hip moments are dependent upon the techniques used to perform the squat. For example, Fry, Aro, Bauer, and Kraemer (1993) observed there was less forward trunk lean in the performance of a front squat compared to a back squat. This study evaluated six subjects who were videotaped in a sagittal view and were evaluated using a static model only at the lowest point of descent. Though not quantified in the paper, this trunk lean would change the moments experienced at the hip during lifting. Futhermore, Wretenberg et al. (1996) used a two dimensional quasi-static approach to 53 evaluate the moments experienced on the knees and hips during parallel and full squats and also when the bar was held in a high shoulder position and low shoulder position. Video footage was recorded of the left side of the body and ground reaction forces were collected via force platform. It was discovered that powerlifters, who use the low bar position, experience relatively larger moments at the hips, but relatively smaller moments at the knee compared to Olympic weightlifters, who use a high bar position. It was also shown that while hip moments did not change dramatically from the parallel squat to the full squat, there was a significant increase in moments at the knee when performing the full squat compared to the parallel squat. RPE and Intensity Rating of Perceived Exertion (RPE) is a means of subjectively quantifying the intensity of a workout. This method of evaluation has primarily been used to evaluate aerobic and anaerobic exercises such as cycling and running. Individuals are asked to personally rate the level of exertion or perceived intensity of exercise based on a number scale with accompanying descriptors. The most common scale used to quantify this intensity is the Borg scale. The original Borg scale was a 15 point scale with a measurement of 6 being the lowest perceived effort (i.e., at rest) and 20 being the highest (i.e., maximal effort) (Noble et al., 1983). A modified Borg scale that ranges from O to 10 (Table 3) has also been adopted in many research studies (Corder, Pottieger, Nau, Figoni, & Hershberger, 2000; Day, McGuigan, Brice, & FOster, 2004; Foster et al., 2001; Noble, Kraemer, & Clark, 1982; Sweet, Foster, McGuigan, & Brice, 2004). Recently, RPE has been used to evaluate the intensity of resistance training workouts. This has been done both as a means of evaluating a single set of exercise and 54 also an entire workout session. In general, use of higher intensity (i.e., more weight) with lower repetitions has been perceived to be more difficult than use of lower intensity (i.e., less weight) performed with high repetitions. For example, Gearhart et al. (2001) reported that initial RPE values were significantly higher for a workout consisting of one set of five repetitions at 90% of lRM compared to one set of 15 repetitions at 30% of lRM. These workouts were designed so that the total work performed was equal. Furthermore, Day et al. (2004) and Sweet et al. (2004) reported that participants rated a set of four repetitions at 90% lRM to be more difficult than a set of 15 repetitions at 50% lRM. In both of these studies, more work was performed in the higher repetition sets, yet the lower repetition sets were perceived to be more difficult. Likewise, the entire higher intensity/lower repetition workout, when evaluated 30 minutes after completion, was rated more difficult compared to the lower intensity/higher repetition workout. Sweet et al. (2004) stated that the session RPE may underestimate the RPE response after each individual set, but RPE does seem to be a valid measure of intensity of the workout. 55 Table 3 Scale for Ratings of Perceived Exertion (Modified Borg Scale) Rating Descriptor 0 Rest 1 Very, Very Easy 2 Easy 3 Moderate 4 Somewhat Hard 5 Hard 6 _ 7 Very Hard 8 _ 9 _ 10 Maximum Rozenek, and Stone (1993) compared RPE values during a workout before and after eight weeks of training. There was a significant decrease in reported RPE values from pre- training to post-training. Additionally, Corder et al. (2000) reported lower RPE values, when moderate (25% maximal voluntary oxygen consumption (MVO2)) active recovery was used between sets compared to no active recovery, and high (50% MVOZ) active recovery. As a whole, RPE appears to be a valuable tool in measuring the perceived RPE is dependent on more than just the intensity of the exercise. Pierce, effort and difficulty of a workout. 56 Effect on Tests of Performance Probably one of the most practical means of evaluation of recovery from a workout of box squats would be to examine the decrements in performance after a weight training workout. However, the determination of what tests of performance to use is difficult due to the limited previous studies evaluating recovery after weight training. Most studies that have evaluated recovery from a weight training session have used tests that are common predictors of ability, rather than assessing actual sport skill performance. This is most likely due to (a) being able to evaluate the results in an objective manner and in a controlled environment and (b) participants not wanting to perform an actual sporting event after a training session. Variables that have commonly been measured are power and maximal force generating ability. Power is often measured by performing maximal vertical jumps. Likewise, maximal force has been measured by isometric contractions against a dynamometer or performance of RMS of weight lifting movements. Few studies have performed actual activities observed in the sport (Kauranen et al., 1999; Linnamo, Hakkinen, & Komi, 1998; Schoenfelt, 1991; Woolstenhulme et al., 2004) while only one known study has investigated changes in anaerobic power due to the weight training (Woolstenhulme et al., 2004). The few studies examining the time rate of recovery after lifting suggests that a moderate strength training protocol would not affect game performance given relatively short recovery times between the session and the competition. Quantification of a moderate training protocol is difficult because many researchers have defined it differently; however, it is often considered to be performing multiple sets (3-4) using an 8 57 to 12 repetition maximum (RM) or performing 8 to 12 repetitions using 67% to 80% of lRM. For example, Kauranen et al.’s (1999) study of untrained women showed no change in motor performance as measured by reaction time, speed of movement, tapping speed, and coordination immediately after acute neuromuscular fatigue was produced by a strength training protocol. The protocol was a circuit workout of twelve exercises where three sets of 15RM were performed for each exercise. Likewise, Raastad and Hallen (2000) observed recovery of knee extension strength and jump squat performance three hours after a bout of moderate intensity exercise with strength trained men. The moderate workout in this training protocol was defined as three sets of three repetitions using 70% of 3RM for back squats and front squats and three sets of six repetitions using 70% of 6RM for leg extension. Additionally, Schoenfelt ( 1991) found no significant decrease in free throw performance immediately after a weight training session in collegiate women. Finally, Woolstenhulme et al. (2004) observed that vertical jump, power output as measured with a Wingate teSt, and basketball shooting accuracy were equivocal to rested performances six hours after a total body strength training session in female collegiate basketball players. The protocol in this experiment consisted of three to four sets of 8-12RM for seven exercises (hang clean, push jerk, bench press, back squat, overhead press, prone leg curl, and dumbbell incline press). These studies would suggest that box squats, performed at a moderate intensity, would not have faster post-training recovery than any other type of moderate strength training of the lower extremity. However, all of these studies have been performed on collegiate students or adults. No known studies have evaluated high school athletes’ ability to recover from a weight training session. Additionally, these studies have not 58 evaluated possible reasons for the decrement in performance after the weight training workouts. Bosco et a1. (2000) reported that partial squats, which are performed at the same depth as box squats, might initially recruit different muscle fibers than parallel squats. This suggestion was due to the fact that averaged EMG values for the quadriceps significantly decreased over several repetitions during the partial squat exercise, while the averaged EMG signal did not significantly decrease during the set of full squats. From this observation, Bosco et al. (2000) concluded that the reduction in force that occurred during the set of partial squats was due to decreased recruitment of muscle fibers, while the reduction in force that occurred during the set of full squats was due to fatigue of the muscle. Evaluation of Weight Training Protocols The questions as to what could be the possible reasons for the differences in adaptations (i.e., faster recovery, greater hip development), if there are differences, between box squats and parallel squats can be speculated on fiom the previously mentioned studies. The amount of EMG activity of the quadriceps should be less for the box squats due to the shallower descent (Wretenberg et al., 1993). However, this may be offset by the fact that more weight is being used (McCaw & Friday, 1994). Analysis of the EMG activity of the muscles of the quadriceps during both of these exercises, and also of partial squats, would allow for a determination if the increase in weight was great enough to require more muscle recruitment regardless of the shallower descent. Comparison of the recruitment of other lower extremity musculature is also of interest due to Caterisano et al.’s (2002) findings that greater gluteal activity occurred with a 59 deeper squat. This would conflict with the statements that box squats “develop the hips to a greater extent.” It can be assumed that moments experienced at the hips and knees should be different due to the different depths of the squat (Wretenberg et al., 1993). These may also be different due to the trunk angle and shank angles that occur when performing the box squat. Anecdotally, it appears that the athletes keep a more upright posture and do not have as much forward excursion of the knees during the performance of box squats. This observation needs to be validated through videographic assessment. These different moments on the lower extremity could be the difference in why fatigue of the legs is less. This evaluation could also lend some determination to the forces experienced on the spine, but as has already been discussed, this could not be truly determined without increasing the invasiveness of the study. It would appear that the differences would be more neurological in nature than hormonal. Differences in hormone response are predominately affected by volume, intensity, and rest periods (Kraemer & Ratamess, 2005). Performing workouts that have equivalent number of sets, repetitions, and rest periods should evoke similar hormonal and metabolic response. The issue that needs to be addressed is determining what would be an equivalent intensity for the two exercises because more weight can be lifted using the lower descending box squats. Thus, even if more weight is used with box squats, but the relative intensity is lower, a slight difference in hormonal and metabolic changes might be observed. Likewise, this difference may require less overall energy expenditure and create a smaller lactate build-up (Linarno et al., 1998). Although unlikely, this acute response difference could be a possible reason for the supposed faster recovery. 60 Monitoring of metabolic changes in blood lactate should be performed to remove this variable from consideration. Assumptions about the changes in testosterone, growth hormone, and cortisol can be made due to the correlation between blood lactate levels and these hormones. The amount of muscle damage may be a more viable indicator in the difference between the two lifts. In theory, more muscle damage should occur performing box squats because of the greater weight used, even if the number of sets, number of repetitions, and length of rest periods were equivocal. This may not be true if the relative intensity of the two lifts is not equivocal. However, these lifts are often performed using multiple repetition maximums and so the relative intensities should be equivocal. Monitoring of the amount of muscle damage as assessed by serum creatine kinase levels should be performed to address this issue. However, this benefit may also be psychological in nature. If the lift is perceived to be less strenuous, then the athlete may experience a “placebo effect.” Perceived exertion during box squats has not been evaluated to determine if it would differ from perceived exertion during parallel squats or any other type of squat. It could also very well be that the box squats are perceived to be more strenuous due to the greater weight being used. Evaluation of RPE needs to be performed to allow for understandings to both of these questions. Simple comparisons of athletes’ ability to recovery via measurement of performance would provide greater insight into differences between box squats and parallel squats. As stated previously, the few studies of performance recovery would suggest there would be no difference. However, tests of power (vertical jump) and 61 maximum force production (maximal isometric leg extension) would validate or refute claims made by BFS. Additionally, a test of anaerobic power endurance would more specifically address the issues of weight training on prolonged performance. Woolstenhulme et al. (2004) used the Wingate test to evaluate this anaerobic endurance. However, a better test may be the Bosco jump test. This test may be more specific to the activities that would be performed in a sporting event requiring prolonged power output such as basketball, volleyball, and gymnastics (Sands et al., 2004). However, this test cannot be directly compared to the Wingate test for anaerobic capacity (Sands et al., 2004) 62 CHAPTER 3 METHODS Research Design This study used a pre-test, post-test, randomized, counterbalanced repeated measures within subject design. It consisted of five sessions (Table 5) which can be summarized as follows: (a) familiarization session and parallel squat 10RM testing, (b) Bosco reference jump test, and (c-e) workout and performance testing sessions 1-3. The purpose of the parallel squat 10RM test was to determine the weight to be used during the workout sessions. The second session provided a measure of anaerobic endurance (i.e., Bosco jump test) in an unfatigued state that could then be compared to post-workout tests. The final three sessions evaluated changes in maximal vertical jump height and anaerobic power, as measured by a Bosco jump test, after completion of each of the three workouts using the different squat lifts (parallel, box, and partial). The workouts consisted of a warm up, reference test, and three sets of 10 repetitions using the parallel squat 10RM weight. During each Of the three workout sessions, electromyographic (EMG), motion analysis, and force platform data were collected. A non-random sample of high school athletes from the greater Lansing area and college fieshmen and sophomores, who were currently weight training and had experience with the squat lifts (parallel, box, and partial), were recruited for participation in this study. All participants had either signed an assent form if they were under the age of 18 years (and parents had signed a consent form), or a consent form if they were above the age of 18 years (Appendix A) prior to participation in the study. 63 The purposes of this study were to: (a) compare the kinematics and kinetics at the ankle, knee, hip, and lower back throughout these lifts; (b) evaluate the differences in recruitment patterns and activation of the muscles primarily thought to be involved in squatting (vastus lateralis, rectus femoris, biceps femoris, gluteus maximus, gastrocnemius, and erector spinae) during acute performances by volunteers of the three lifts (parallel, box, and partial squats); (c) evaluate the pre- to post-squat lift (parallel, box, and partial) differences in various performance parameters (i.e., maximal vertical jump and Bosco jump test); and ((1) compare these performance parameters to perceived exertion and fatigue as measured by the modified Borg scale. Participants Participants were male high school students who were currently using the Bigger Faster Stronger program (BFS) as a method of weight training at their high schools or college freshmen and sophomores who were currently lifting and had experience with the three squat lift techniques (parallel, box, and partial). Males were chosen because the BFS program tends to be more prevalently used by football coaches to train their athletes. All high school athletes were between their sophomore and senior years, were currently weight training, and had a minimum of one year experience weight training and six months experience performing both parallel and box squats. The college students were expected to meet the same criteria and, in addition, were also expected to have been lifting at least twice a week for six months immediately prior to participating in this study. All participants were currently free from orthopedic injuries; in particular, injuries to the lower back and lower extremities. 64 Selection Criteria High school participants were recruited from schools that use the BF S program or that incorporate box squats into their weight training programs. College students were recruited by flyers posted in their campus intramural buildings and by an investigator soliciting students in undergraduate Kinesiology courses. It was required that the participants had six months experience with the techniques of box and parallel squats. A questionnaire (Appendix B) was designed to screen participants for injuries to the lower back and extremities (shoulder, arm, elbow, forearm, wrist, hands, hip, thigh, knee, shank, ankle, and foot) that may influence their squat lift techniques. Parents of the high school athletes filled out this questionnaire while the college athletes were permitted to fill out their own questionnaires because they were all 18 years of age or older. Recruitment Athletic directors, coaches, and/or athletic trainers of local high schools were contacted and were asked if their weight training programs were based on the BFS program or if their weight training programs included the box squat and parallel squat. Athletic directors/coaches/trainers of the schools that did incorporate these two lifts in their weight training programs were initially asked if they would be willing to discuss the proposed study and determine their willingness to allow their athletes to be recruited before proposing the study to their school boards. After receiving permission from the athletic directors and the school boards, times and dates were arranged to make presentations about the study to the potential student participants. Parents/ guardians of students that were interested were then contacted via phone and were asked if the permission forms (Appendix A) could be sent home with the potential participants. A 65 second call or a meeting was then scheduled to answer all questions prior to parents and participants filling out and signing the consent/assent forms (Appendix A). Signed consent and assent forms were required for each high school student before permitting participation in this study. College students were recruited by flyers posted in their campus intramural buildings and by an investigator soliciting students in undergraduate Kinesiology courses. An initial meeting was scheduled with potential participants where the details of the experiment were explained. The participants were then provided with the consent form and screening questionnaire (Appendix B). Forms were signed and returned prior to permitting participation in the study. Sample Size Sample size was determined by power analysis (Cohen, 1988). It was desired to have between 18-36 participants due to evaluating power from previous squatting studies that evaluated muscle activity and/or joint moments. This goal was not met. The primary reason for the limited number of participants was the time commitment required. Athletes that were currently participating in a sport could not participate due to practice commitments and the possible effects of their practices and games on the testing. Many potential participants who were not participating in sport had other commitments that made it impossible to complete all five testing sessions in the desired time frame. Likewise, the extended length of the last three testing sessions (approximately five hours) was a deterrent to many participants. Additionally, the fact that four testing sessions had to be completed at Michigan State University, instead of at the high schools that these athletes were being recruited from, caused even more disinterest. A monetary reward and 66 T-shirt were offered for participation in the study, but these incentives were still not enough to increase participation. Even though the initial sample size goal was not met, a minimum power level of .80 or greater was obtained on 19 of the 25 dependent variables with the sample size of seventeen that was Obtained. Instrumentation Instrumentation used in this study included electromyography (EMG), motion analysis equipment, reflective markers, force platforms, weight bar, weights, anthropometers, Vertec, and ratings of perceived exertion (RPE) scale (Borg Scale). EMG EMG was collected using a MYOPAC telemetric system (Run Technologies, Mission Viejo, CA). EMG was recorded on the right side of the body for the erector spinae (3 cm lateral to the L2 through L4 spinous processes), gluteus maximus (halfway point between the sacrum and greater trochanter), biceps femoris (halfway point between the ischial ramus and lateral epicondyle of the femur), gastrocnemius (one hand width below the popliteal crease on the lateral mass of the calf), vastus lateralis (one hand width above the patella and then the lateral, central portion of the muscle belly), and rectus femoris (halfway point between the anterior superior iliac spine (ASIS) and patella) (Perotto, 2005) . Additionally, a single electrode was placed on the left clavicle to serve as a ground reference. Figures 6-8 provide illustrations of the electrode placement. Prior to the placement of the electrodes, the skin at the electrode sites was prepared by shaving, abrading, and using rubbing alcohol to reduce electrical resistance. Silver chloride 67 electrodes (Ambu Blue Sensor SE, SE-OO-SSO, Ballerup, Denmark) were placed 3 cm apart on muscle bellies of selected muscles. A portable EMG belt unit was strapped around the torso of the participants (Figures 6 & 8). Electric leads were then attached from the portable belt unit to the electrodes and the signals were transferred to the MYOPAC system via optic cable. The EMG system was synchronized with output from the force platforms and motion analysis cameras and data were sampled at 1000 Hz. Gain was set at 1000 while input impedance was one megaohm and common mode rejection ratio was 110 dB minute at 60 Hz. EMG Electrode for the Ground Reference iii.» :$1.fu ‘ ' 3 Portable ' l“ ‘ Belt Unit EMG Electrode Pair for the . - , - ....-W ' ‘ Z” Rectus Femoris EMG Electrode " Pair for the Vastus Lateralis Figure 6. Anterior frontal plane view of EMG electrode placement and portable belt unit. 68 ~,r......,.-. Fair for the y . Erector Spinae "'1': ' I , ,' f Erik-....- i. ""4””! ‘ $21111 ' ' ' "3531!. EMG Electrode .2 J i Pair for the f Gluteus ; ‘ i H . - EMG Electrode "E..- Pair for the EMG Electrode ""7? Rectus F emoris Pair for the t ,- Biceps Femoris ~ ' 5 4351-3 ‘2' Hr.- mu. . ¢ .1113: 2 ~.' “:11:- ‘i '.i':~ ' EMG Electrode . ' Pair for the if. t. 5; EMG Electrode f‘} " ". Pair for the ...-.1 '- w-J. {gi‘é' 3.2.335. I 3: :2: -. Gastrocnemius x- Heat’s. {£33333 Figure 7. Sagittal plane view of EMG electrode placement and position of two force platforms. L... ..‘r ..-. . ... » '4‘- ‘.;ie.-.. "it'd-EEE‘S‘ZR . ti; 69 E G Electrode EMG Electrode Pair for the Pair for the ' Gluteus aximus Erector Spinae Portable EMG Belt Unit 3 "_ if; Pair for the 1 - -- ‘1 Vastus Lateralis maze 1:322: EMG Electrode Pair for the Biceps Femoris .. ‘.~ ’ ‘ ‘ . ' EMG Electrode i "1‘“. Fair for the . ’ ‘ Gastrocnemius \ 4, _., . _ , A .-. I .. Figure 8. Posterior frontal plane view of EMG electrode placement and portable belt unit. Motion Analysis Two dimensional digital motion analysis of the sagittal plane was performed on the squat lifts. Data were collected from the right side of the body. Six Vicon Mx3+ infrared cameras with 6-8 mm variables lenses (Vicon, Los Angeles, CA) were placed at 70 variable heights approximately three meters from the participant’s right side (Figures 9- 10). Two participants were analyzed with only three cameras because only three cameras were available at the time of their data collection. In addition, a Basler 602f digital video camera (Basler Vision Technologies, Exton, PA) was used on some trials to provide video images of the workouts. These video images were not recorded for every trial due to the size of the image files created and the Basler camera causing technical problems with the Vicon computer. The video was not needed for analysis Of the exercises and only provided a qualitative reference. ,1_'.'..i.rr ‘r‘“ ;, .. {2.34, .. .. . ”1.3:” 9.1,». ’1‘ 4. (1 \ )1 v \I, " damask? ..I ’ Infrared Cameras Figure 9. Arrangement of infrared cameras and force platforms for data collection. (Note that the view of the sixth camera (denoted by the dashed arrow) is blocked by the lab wall. See Figure 10.) 71 4 MfiWWZT‘Hi'PT‘tLHE-k‘n. i ‘,'.;"v‘P'.-..n . _ . ....-. Vicon EMG ContrOI Unit 13’3““ Control Unit Force Platform 11: Amplifiers . , ,. . , \v ’7.' 5 L ., J ‘ ‘ a" x‘ -;7‘,‘ b ., Figure 10. Arrangement of infrared cameras, Vicon computer, and force platform amplifiers. Reflective markers were placed on the second metatarsal, lateral portion of the fifth metatarsal head, lateral malleolous, calcaneous, mid-shank (anterior and lateral), lateral epicondyle of the femur, mid-thigh (anterior and lateral), greater trochanter, anterior superior iliac spine, and superior aspect of the iliac crest (Russell & Philips, 1989) on the right side of the body (Figures 11-12). Markers were also placed on the jugular notch and xiphoid process of the sternum and the end of the weightlifting bar. Markers placed on wand extensions were placed on the mid-thigh (lateral) and sacrum (Figures 11-12). The wand extension was used on the mid-thigh so that there would not 72 be three co-planar points which would not allow the Vicon software to determine the direction of the angle. The wand extension was used on the sacrum to prevent EMG wires from blocking the marker. These markers were recorded by the infrared cameras and were used to create the reference model of the participants. The distance from the end of the bar to the shoulder was measured via tape measure and recorded for future analysis. 73 Superior phiod Process 2 . i Iliac Crest Greater Trochanter Anterior Superior Lateral Mid-thigh Lateral Epicondyle An . of Femur .terior Mid-thigh Lateral Mid-Shank ”w“ Anterior Mid-shank Lateral ' A Malleolus 5th Metatarsal Head Figure I I. Anterior frontal plane view of reflective marker placements. 74 End of Bar Superior Iliac Crest 4 Xiphoid Process Sacrum Anterior Superior Iliac Spine Greater Trochanter _.- ‘ ' Anterior ‘ Mid-thigh Lateral k Mid-thigh . Lateral Epicondyle of the Femur Lateral Mid-shank V. Anterior .. :s‘ Mid'Shank Lateral Malleolus 2"d Metatarsal Head Calcaneus '-* 5th Metatarsal Head Figure 12. Sagittal plane view of reflective marker placements. 75 Prior to data collection, the infrared cameras were calibrated using a calibration wand (Figure 13). The wand was initially placed at the global origin to aim the Vicon cameras. The wand was then moved in curvilinear patterns throughout the space in which the exercises would take place (capture volume) to calibrate the Vicon system. Each camera recorded 1000 fields of the five reflective markers for calibration. Calibration was considered satisfactory if less than .15 pixels per pixel error was reported. The Vicon system was recalibrated until this level of calibration was achieved. Calibration Wand with Reflective Markers Figure 13. Force platforms and calibration wand at global reference point. 76 Force Platforms On all workouts, vertical and horizontal ground reaction force data were collected from the interface between the right foot and the force platform imbedded in the walkway platform. Additionally, reaction data were collected from the interface between the buttocks and a second force platform during the box squats. Participants stood with their right foot on an Advanced Mechanical Technology Incorporated (AMTI) force platform model OR6-5-1000 (AMTI, Watertown, MA) that was embedded into a walkway platform. A second AMTI force platform (model OR6-5-2000) was mounted on an adjustable box located directly behind the participants during the box squat session (Figure 14). These commercially marketed force platforms were calibrated by the manufacturer. The box was braced against the elevated walkway platform using an adjustable jack to minimize movement of the box during the exercise. Data were collected at 1000 Hz and was synchronized with the EMG and motion analysis data. One participant had his force platform data collected at 100 Hz due to an unexpected problem with the Vicon system. However, this did not affect the analysis because the force platform data were reduced to 100 Hz when combined with the motion analysis data to determine the reaction forces and moments at the joints. 77 ‘t‘rii‘ _ Platform Extension r.. . 1 ‘ . ' ‘1. _-R¢ Adjustable Box Walkway Platform Figure 14. Arrangement of force platforms and adjustable box for box squat session. Anthropometric Measurements Anthropometric data were collected to provide a general description of the participants’ bodies. A scale, stadiometer, and short anthropometer were used during the collection of the anthropometric data. The following describes the procedures that were used to collect the anthropometric data (Brown, 2004). 1. Weight: Weight was measured on a standard electric scale while the participants were in athletic attire (shorts and t-shirt only). 78 2. Standing height: The participants stood erect with body weight evenly distributed on both feet. Heels were placed together and in contact with the wall. The wall was free of molding and formed a right angle with the floor. Arms were hung freely at the sides of the body. The head was positioned in the Frankfort plane. The participants were asked to take in a deep breath and get as tall as possible without their heels leaving the floor. The sliding bar of the stadiometer was brought down on the vertex of the head with sufficient pressure to depress the hair. 3. Sitting height: The participants sat on a bench with the hips and back against the wall making sure to sit upright as much as possible without contracting the muscles of the buttocks or thigh. The participants were asked to take in a deep breath and get as tall as possible. The sliding bar of the stadiometer was brought down on the vertex of the head with sufficient pressure to depress the hair. 4. Foot length: The participants stood erect with both upper extremities fully extended at the sides of the body and the palms positioned medially. The right foot was placed on a bench that allowed the knee to be flexed to approximately 90 degrees. The anthropometer was placed in the transverse plane. The distance from the lower part of the heel (calcaneous) to the tip of the big toe was measured. 5. Ankle width: The participants stood erect with both upper extremities fully extended at the sides of the body and the pahns positioned medially. The right foot was placed on a bench that allowed the knee to be flexed to approximately 90 degrees. The anthropometer was placed in the transverse plane. The distance from the medial to lateral malleolus was measured. 79 6. Shank length: The participants stood with the right foot on a bench that allowed the knee to be flexed to approximately 90 degrees with the shank perpendicular to the top of the bench. A pen mark was made on the lateral ridge of the tibia. The anthropometer was positioned in the sagittal plane and perpendicular to the floor. The fixed end of the anthropometer was placed underneath the lateral malleolus. The sliding bar of the anthropometer was then raised to the pen mark. 7. Knee width: The participants stood erect with both upper extremities fully extended at the sides of the body and the palms positioned medially. The right foot was placed on a bench that allowed the knee to be flexed to approximately 90 degrees. The anthropometer was placed obliquely in the transverse plane. The distance from the medial to lateral epicondyles of the femur was measured. 8. Femur length: The participants stood with their feet shoulder width apart and body weight evenly distributed on both feet. The anthropometer was positioned in the sagittal plane and perpendicular to the floor. A mark/piece of tape was place on the lateral portion of the greater trochanter. The fixed end of anthropometer was placed on the tape mark. The sliding bar of the anthropometer was then lowered to the pen mark placed on the lateral ridge of the tibia. 9. Bi-iliac breadth: The participants stood erect with their back to the examiner. Body weight was evenly distributed on both feet, which were shoulder width apart. The iliac crests were palpated with the index fingers. The ends of the bow caliper were placed on the lateral sides of the crests at those points that resulted in the greatest hip breadth. The caliper was held in the transverse plane. Pressure was applied to the ends of the caliper to compress the skin and adipose tissue. 80 10. Trunk length: The participants stood with their feet shoulder width apart and body weight evenly distributed on both feet. The anthropometer was placed in the sagittal plane. The distance from the top of the lateral projection of the superior portion of the humerus (just below the lateral projection of the acromion) to the most superior point of the iliac crest was measured. 11. Bi-acromion breadth: The participants stood erect with their back to the examiner. Body weight was evenly distributed on both feet, which were shoulder width apart. The acromion processes were palpated with the index fingers. The ends of the bow caliper were placed on the lateral sides of the processes at those points that resulted in the greatest shoulder breadth. The caliper was held in the transverse plane. Pressure was applied to the ends of the caliper to compress the skin and adipose tissue. V ertec A commercial Vertec (Sports Imports, Columbus, OH) vertical jump device was used to determine maximal vertical jump height. The Vertec allows vertical jump height to be measured in half inch increments. The Vertec was set so that a participant could touch the measuring vanes while standing with his dominant arm fully outreached over his head (Figure 15). The highest vane reached was pushed forward and recorded. The Vertec was then adjusted to accommodate the potential maximum jump height of the participant. The participant then performed a two legged countermovement jump without a stutter step (Bachle & Earle, 2004). The participant jumped as high as possible and reached to displace the vanes of the Vertec (Figure 16) with the fingers of his dominant hand. The height of the highest vane moved out of position was subtracted from the standing reach to determine the maximum vertical jump. Three attempts were performed 81 on all occasions and the maximum of the three attempts was used as the maximum jump height of the participant. Over the course of all vertical jump testing, measurements were performed by three individuals, who recorded the data either by themselves or as a group at the time of testing. All testers had training prior to data collection using the methods outlined previously (Baechle & Earle, 2004). Although no formal intertester reliability was performed, two testers were often present for the pre-workout vertical jumps and these testers confirmed each other’s ability to determine the height of the jump. The vertical jump test has been shown to have test-retest reliability of .977, objectivity of .99, and concurrent validity (horse power) of r=.989 (Tritschler, 2000). Furthermore, the vertical jump test is long standing test of power in sport testing that has well established norms for various levels of athletes (Baechle & Earle, 2004). Bosco Jump Test Participants started with their right foot situated on a force platform (AMTI ORG- 5-2000). Prior to initiating the test, each participant was positioned so that he had a reference of proper depth to obtain on each counterrnovement. The method to determine this depth was similar to determining proper depth for the parallel squat. Participants squatted until a 90 degree angle was formed at the knee. This angle was measured by a manual goniometer. The depth was referenced by placing a bungee cord such that the bottom of the thighs came into contact with the taut bungee cord at the proper depth (Figure 17). 82 Figure 15. Maximum reach test using a Vertec. 83 ’Wn "w Figure I 6. Participant performing maximal vertical jump test using a Vertec. 84 Figure 17. Proper jump depth for the Bosco jump test. 85 The Bosco jump test then commenced. Participants maintained their hands on their hips during the entire testing session. On the command to start, participants repeatedly performed countennovements to the 90 degree depth followed by maximal vertical jumps for 60 seconds. During this time, the force platform collected vertical ground reaction force data from the right foot at a sampling rate of 100 Hz. These data were saved on a computer for future analysis. The Bosco jump test has been tested for reliability and validity with athletic populations. Bosco et al. (1983) reported test-retest reliability correlation of F.95 when the Bosco test was performed in an unfatigued state. This study was performed by an Italian male volleyball student team (n=12, mean age = 21.7). Likewise, Sands (2000) reported an intraclass correlation coefficient of .87 when evaluating test-retest reliability (tests one month apart) on athletes preparing for the Olympic games. Furthermore, Sands et al. (2004) reported that college male track athletes had statistically significant correlation between average power produced in a Wingate cycle test compared to average power produced in a Bosco jump test (r=.89, p<.001). The Wingate test has had more extensive validation and this correlation would suggest that the Bosco jump test is a valid and reliable measure of anaerobic endurance. Borg Scale A modified ten point Borg rating scale of perceived exertion (RPE) was used (Table 4). RPE’s were obtained from participants after each set of the workout and immediately after the entire workout. The participants were shown the modified ten point Borg rating scale. The verbal cue used after each set was “rate your overall effort.” The verbal cue after the entire workout was “rate your overall workout.” 86 RPE has been shown to be a reliable and valid method of assessing intensity Of a weight training session. Day et a1. (2004) reported intraclass correlation coefficients of .88 for test-retest reliability using a modified Borg scale to measure weightlifting intensity performed on two separate testing days. Furthermore, Day et a1. (2004) and Sweet et al. (2004) have reported that RPE values increase with increasing intensity (i.e., weight) during resistance training even when volume decreases. Table 4 Scale for Ratings of Perceived Exertion (Modified Borg Scale) Rating Descriptor 0 Rest 1 Very, Very Easy 2 Easy 3 Moderate 4 Somewhat Hard 5 Hard 6 _ 7 Very Hard 8 _ 9 _ 10 Maximum 87 Testing Procedures An outline of the testing procedures is provided in Table 5. A detailed description of each session follows. Table 5 Outline of Experimental Sequences and Procedures Session One- F arniliarization and 10RM Testing 1. 5. 6. Returning of assent, consent, and screening questionnaire forms (Appendixes A & B) Completing previous 48 hour activity questionnaire (Appendix B) Warming up/stretching Farniliarizing participant with testing protocols Testing of 10RM for parallel squat Practicing of the Bosco jump test Session Two- Reference Bosco Jump Test (Minimum of 48 hours after Session 1) l. 2. Complete activity questionnaire (Appendix B) on previous 48 hours Warm up/stretching Bosco jump test Weight recorded Possible taking of anthropometric measurements 88 Table 5 Continued Sessions Three through Five - Workouts and Performance Testing (Sessions minimum of 48 hours apart) 1. 2. 10. 11. 12. 13. 14. 15. 16. COmplete activity questionnaire (Appendix B) on previous 48 hours Weight recorded Placement of EMG electrodes Warm up/stretching Vertical jump pre-test Placement of reflective infrared markers 2 static trials 2 warm up sets using 50% of parallel 10RM (1 minute rest between each) Reference test using parallel 10RM (3 minutes rest after completion) Workout (3 sets of 10 repetitions (using parallel 10RM weight) of either box, parallel, or partial squats) RPE evaluation between workout sets and after entire workout Vertical jump post-test Participants’ EMG electrodes marked with Henne dye Possible taking of anthropometric measurements 3 hours post-exercise-maximum vertical jump test 3 hours post-exercise-Bosco jump test * Henne dye was placed around the perimeter of EMG electrodes during session three and, if the prior dye marks had faded, it was re-applied during session four. 89 Session One-Familiarization and 10RM Testing Each participant had previously been informed of the testing procedures and had either previously turned in the consent and/or assent forms or turned the forms in prior to the start of the session. Procedures were reviewed and any questions about the procedures were clarified. Parents and coaches (if present) were allowed to observe the rest of the testing session. Each participant filled out a 48 hour exercise questionnaire prior to the start of the session (Appendix B). The testing session then consisted of a warm up, ten repetition maximum (10RM) test, and practice of the Bosco jump test. Warm up. The following warm up was used for each session. Each participant performed a five minute warm up on a cycle ergometer at a comfortable pace. Stretching followed, with each stretch being held for 30 seconds for each side of the body except the groin stretch, which was only performed once with both legs at the same time (Shepard, 2004a). The following is a description of each stretch for the right side of the body. 90 Figure 18. Calf stretch. 1. Calf stretch: The participants stood with the soles of both feet flat on the ground in a staggered stance. The right lower extremity was extended in a straight line behind the torso while the left lower extremity was out in front of the torso and the left knee was in approximately 30 degrees of flexion. The torso was held upright and both hands were placed against a wall to provide support. The hips were moved forward to cause a stretch in the muscles of right calf. The lower extremity positions were switched and the stretch was repeated for the other side of the body. 91 Figure 19. Standing quadriceps stretch. 2. Standing quadriceps stretch: The participant stood on the left foot while the right foot was brought to the buttocks. One hand may have been placed on a wall for support. The participant had the choice of which hand was used for support and which hand was used to hold the right forefoot. The right forefoot was grasped and pulled straight back to stretch the quadriceps. The lower extremity positions were switched and the stretch was repeated for the other side of the body. 92 Figure 20. Gluteus maximus stretch. 3. Gluteus maximus stretch: The participant was seated with both lower extremities extended straight out in front of the body. The right lower extremity remained straight and supported by the floor, while the left lower extremity was bent to approximately 90 degrees and placed over the top of the right lower extremity. The participant attempted to place the left foot on the ground. The right arm then reached across the midline of the body. The torso was twisted by pressing the right arm against the left thigh. The lower and upper extremity positions were switched and the stretch was repeated for the other side of the body. 93 Figure 21. Hip flexor stretch. 3. Hip flexor stretch: The participant started in a kneeling position. The right thigh was brought to a position in front of the torso so that the foot was flat on the ground and the shank made a 90 degree angle with the floor. The left knee was slightly behind the torso with both the left knee and toes in contact with the floor. The hands were placed on the right knee to help maintain an upright torso. The hips moved slightly forward and down. The lower extremity positions were switched and the stretch was repeated for the other side of the body. 94 Figure 22. Groin stretch. 5. Groin stretch: The participant was in a seated position with the bottom of the feet pressed together. The feet were then pulled in toward the body while the elbows pressed down on the thighs. 95 'fl ("1"? fr‘b‘fi‘flb“ "_ N . .6 . z . 2‘ E I 3 . . . i T u t} . ,‘ i . ~. I r‘ l a I"._ Figure 23. Hamstring stretch. 6. Hamstring stretch: The participant sat with the right lower extremity extended straight out in front of the body and supported by the floor. The left lower extremity was bent at the knee and the sole of its foot was placed against the inner thigh. The participant leaned forward while keeping the back straight to cause a stretch in the hamstring. The lower extremity positions were switched and the stretch was repeated for the other side of the body. 96 F amiliarization to testing protocols. Each participant was shown proper procedures and movement patterns for the 10RM testing session. Afterwards, each participant was measured for proper depth of parallel squat. This was accomplished by having the participant place a barbell on the back/shoulders and perform a squat so that top of the thighs were parallel to the ground. This depth was recorded by placing a taut bungee cord at the desired height so that the bottom of the thighs came into contact with the bungee cord at this low point in the squat (Figure 24). 10RM testing. A 10RM test for the parallel squat was performed. An outline of the 10RM test is included in Table 6. A minimum of two experienced spotters were present for all attempts. One spotter was directly behind the participant while the other monitored from the side and confirmed proper depth was reached. If other spotters were present, they were placed on both ends of the bar and followed the movement of the lifter, keeping their cupped hands approximately 5-8 cm below the bar throughout the movement and assisting with the lifting of the bar during a failed attempt (Baechle & Earle, 2000). Participants were also measured for box and partial squat depth. This was sometimes performed after the parallel squat test, but happened more often after the second session. The box height was adjusted in increments of one half inch so that the knee angle was as close to 90 degrees as possible when the buttocks contacted the box (Figure 25). Partial depth was determined in the same manner as the parallel squat except the criteria was a knee angle of 90 degrees at the low point in the squat (Figure 26). 97 Bungee Cord - ’ Figure 24. Example of proper bungee cord placement so that the top of the thighs are parallel to the ground at the low point in the squat. 98 Table 6 Temporal and Sequential Order for 10RM Testing (Modified from Baechle & Earle, 2000) Warm Up 1 set of 10 repetitions at 50% estimated 10RM followed by 1 minute rest 1 set of 5 repetitions at 75% estimated 10RM followed by 2 minutes rest 1 set of 5 repetitions at 85% estimated 10RM followed by 3 minutes rest 10RM Test 1 set of 10 repetitions at estimated 10RM Completion Criteria: A. If the participant completed 9 out of 10 repetitions with proper form and the 10‘h repetition had minimal loss in form (within v2 inch of proper depth, only mild increase in forward trunk lean), the testing was stopped and the weight used was recorded as the 10RM. B. If the participant completed 10 out of 10 repetitions with proper form, the 10RM test was repeated after 3-5 minutes rest using a weight between 101-110% of the weight that had just been completed (participant’s choice). If this second 10RM test was successfirl (met the criteria described in B.), the 10RM test would be repeated again using the same procedures as in B. above (this step not repeated more than two times). If the second 10RM only met the criteria described in A., then the testing was stopped and the weight used in the second 10RM test was recorded as the 10RM. If the second 10RM met the criteria described in C., then either the testing was stopped and the weight that was completed in the previous 10RM test was recorded as the 10RM or the 10RM test would be repeated using the procedures described in C. 99 Table 6 Continued Completion Criteria: C. If the participant had more than minimal loss of form on the last repetition or could not complete the 10 repetitions, the test was repeated after 3-5 minutes rest using 90-100% of the weight from the previous set (participant’s choice). If this second 10RM test was successful (met the criteria described in B.), the 10RM test would be repeated again using the procedures described in B. (this step not repeated more than two times). If the second 10RM only met the criteria described in A., then the testing was stopped and the weight used in the second 10RM test was recorded as the 10RM. If the second 10RM met the criteria described in C., the testing would be repeated using the procedures described in C. (not repeated more than two times). No participant performed more than three sets of the 10RM test even though a maximum of four sets could have been performed. 100 ‘I ‘31:.“ ‘f .\ Au. 1923522" Figure 25. Proper box squat depth. 101 (a) (b) (C) Figure 26. Comparison of lowest point of descent for (a) box, (b) parallel, and (0) partial squats. Practice Bosco jump test. The participants were allowed full recovery (i.e., typically five minutes) from the 10RM testing and then performed a familiarization session for the Bosco jump test. The purpose of practicing this test at the end of session was to reduce the possibility of a “learning effect” (increase in performance due to having performed the test previously) in the subsequent testing sessions. Performing a familiarization trial allowed for a “truer” baseline value. Session T wo- Reference Bosco Jump Test The purpose Of the second session was to perform a Bosco jump test in an unfatigued state that could be used as a baseline comparison to the Bosco tests that occurred after the workouts (i.e., after sessions three — five). This session was scheduled a minimum of 48 hours after the first session and a minimum of 48 hours before the third session. Each participant filled out a 48 hour exercise questionnaire (Appendix B) prior to the start of the session and had his weight measured prior to performing the Bosco 102 jump test. Participants performed the same warm up as described in the session one workout. The participants performed the Bosco jump test as described in the Instrumentation section of this chapter. After the Bosco jump tests, participants’ weights were measured, proper box and partial squat depth were determined (if not determined during session one) and, if time allowed, anthropometric measurements were taken. Anthropometric measurements were taken at the end of the second session or during the recovery time of one of the last three sessions. Each participant was measured for specific anthropometric parameters previously listed. The secondary investigator performed all anthropometric measurements. Appendix C provides information about the anthropometric measurement ability of the secondary investigator. Sessions Three through Five Sessions three through five had the same format. The participants arrived at the Biomechanics Research Station and reviewed the procedures for the testing session. Each participant filled out a 48 hour exercise questionnaire (Appendix B) prior to the start of the session. Participants then had their weight measured and the EMG electrodes applied to the muscles of interest after the skin was shaved, abraded, and cleansed. These procedures are described in the Instrumentation section of this chapter. Warm up, as previously described, was performed after all EMG electrodes were in place. The participants then performed three maximum vertical jumps using the Vertec and methods described in the Instrumentation section of this chapter. After completion of the three vertical jumps, the participants were prepared for the workout and motion analysis recording. Reflective markers (as described in the Instrumentation section) were placed on the participants and the EMG instrumentation 103 was attached to the electrodes. Two static trials were recorded prior to the start of the testing. The first static trial consisted of the participant standing upright with his hands on his head. The purpose of this trial was to determine the angle offsets for the ankle and knee (described in the Data Analysis section of this chapter). The second static trial was of the participant standing erect with an unweighted bar across the back/shoulders. The distances between the reflective markers of the shank (lateral malleolous and lateral epicondyle), thigh (lateral epicondyle and greater trochanter), and pelvis (greater trochanter and superior iliac crest) were calculated using the Vicon motion analysis system. These distances were used as a reference distance for placement during sessions four and five. Markers were adjusted during sessions four and five until they were 0.5 cm or less different from the original placement. The marker on the iliac spine was removed after the static trials. Two warm up sets often repetitions each using 50% of the 10RM (workout weight) were then performed. These warm up sets were performed using the type of lifting that was randomly assigned for that day for each specific participant. One minute rest was allowed between warm up sets. Reference test. The reference test was performed immediately after the two warm up sets. The reference test was a single repetition using the 10RM weight held in the parallel squat position for three seconds at the lowest point of descent. In other words, participants were instructed to descend to the parallel squat depth and hold that position for four seconds to ensure that a three second isometric contraction was held. Three minutes of recovery was allowed before starting the workout. 104 A workout using either parallel, box, or partial squats was then performed. Participants were randomly assigned to one of the six possible orders that could occur (Appendix D). All workouts consisted of three sets of ten repetitions using the parallel squat 10RM weight. RPE was recorded after each individual set and after the entire three set workout. Three minutes rest was allowed between each set of squats during the workout. Fifteen minutes after the completion of the third workout set, three more maximum vertical jumps were performed. This time frame was maintained on all but one occasion. On that occasion, the jumps occurred 25 minutes after completion of the third workout set. It was determined to include this maximum vertical jump data because the decrease in jump height (i.e., post-workout height compared to pre-workout height) for this particular participant was not statistically different (2 score >3.0) than the decrease in vertical jump experienced by the other participants performed at 15 minutes post- workout. The participants were allowed to eat and rest for three hours after these tests. The three hour time was started from the moment of finishing the last set of 10 repetitions. A room was provided to allow participants to eat, read, watch movies, and engage in relaxing activities during this rest period. Some participants had their anthropometric measurements taken during the rest period. At the end of the three hour recovery time, the maximum vertical jump test was again performed and the Bosco jump test immediately followed. The participants were marked using Henne dye after the third session (Figure 27). The dye was placed around the perimeter of the pairs of electrodes on the participants 105 after the 15 minute post-vertical jumps and was left on between one to two hours to stain the skin. These marks were then used to place the electrodes during sessions four and five. The marks were re-dyed, replicating the former dye mark locations, after session four if they were deemed to have faded drastically. Figure 27. Henne dye markers showing the perimeter of the pairs of electrodes used on the vastus lateralis and rectus femoris. 106 [I si Squat Lift Techniques Each participant started with the right foot on a force platform imbedded in the walkway platform. A second force platform was mounted on an adjustable box, located directly behind the participant when the box squat was performed (Figure 25). The researchers and spotters reminded all participants to “not let their back relax” when in the seated position on the force platform and to keep their back in a “natural position.” A “natural position” was understood to be when the normal curvature of the spine was maintained in the seated position. This was facilitated by using the BF S terminology of “sitting tall and spreading the chest” (Shepard, 2004b). Descent occurred in a self selected pace. The goal was to mimic the lifting pattern that occurred in each participant’s normal workout. Beginning in a standing position, the participant sat down completely on the box, paused for an instant, and then completed the concentric portion of the lift by returning to the original starting position. Several of the participants completed the box squat with a “toe raise” (plantar flexion at the ankles) at the end of the ascent as this was how they normally performed the exercise in their workouts. The partial and parallel squats were also tested using the parallel squat 10RM load. For the partial squat, depth of descent was the same as the box squat, but instead of sitting down on a box, a taut bungee cord was placed behind the participant to signal the appropriate depth of descent. The partial and parallel squats were performed without a pause because that is how they were normally performed in training. The technique of the parallel squat differs from the partial squat only in the depth of descent (Figure 26). All other aspects were performed as normally would be done in training. 107 al. Data Analysis EMG Time points of the important events of the lift (start of the eccentric phase, start of the concentric phase, finish of the lift) for the first set and the reference test (start and finish of isometric hold) of each participant were identified using the Vicon motion analysis system. The eccentric phase was the time between the start of the squat and the attainment of the lowest position and the concentric phase was the time between the start of the ascent and the attainment of the original starting position. The start of the eccentric phase was identified by evaluating when the knee angle started to decrease (i.e., the knees started to flex). The start on the concentric phase was identified by determining when the end of the bar started to ascend. The finish of the lift was identified by determining when the bar was no longer ascending (i.e., the bar’s vertical position no longer increased). The EMG data were analyzed using DATAPAC software (Run Technologies, Mission Viejo, CA). The data were filtered using a 10 Hz high pass Butterworth filter and then full wave rectified. Repetitions three through nine of the first set were used for analysis. Each eccentric and concentric portion of the EMG signals of the seven repetitions were integrated (IEMG) and then divided by the time of each phase to get an average integrated value for each phase. EMG was analyzed in two different methods. First, it was evaluated for relative contribution of each muscle to the repetition. The protocol was the same as Caterisano et a1. (2002) except the erector spinae muscle was added into the total muscle activity and the contribution was calculated for the eccentric and concentric portions of each 108 repetition. Total muscle activity was calculated as the sum of all average IEMG for the six recorded muscles for each phase of the testing. Each muscle’s contribution was divided by the total muscle activity to give a normalized contribution to the repetition and these values were compared across workout conditions. Second, the muscle activity of each repetition (eccentric and concentric portions) was normalized to the reference test and compared across workout conditions. In both cases, 2 X 3 (eccentric/concentric X workout condition) ANOVAs with repeated measures on both variables for each muscle were used to determine if muscle activity was statistically different. A Bonferoni adjustment was used for the six muscles and so an alpha level of .008 was the criteria for statistical significance in all cases. Motion Analysis and Force Platform Data Data were analyzed using Vicon Nexus and BodyBuilder software (Vicon, Los Angeles, CA). The center of pressures of the ground reaction forces from the force platforms were identified using the Nexus software. Marker positions were analyzed using a model created in BodyBuilder software (Appendix E). A five segment model (foot, shank, thigh, pelvis, and trunk) was used for analysis of joint angles, forces, and moments. The reflective markers placed on the 2"d metatarsal head, lateral malleolous, lateral epicondyle of the femur, lateral and anterior mid-thigh, greater trochanter, and end of the bar were used to develop this model (Figures 11-12). Figure 28 depicts this model. The BodyBuilder software required use of all three dimensions (X, Y, and Z) to define the body segments; however, due to the restrictions of the laboratory space and camera placement, it was decided to evaluate movement only in the sagittal plane where the majority of movement occurs during squatting exercises. The global reference was 109 set so that the X direction was in the frontal plane and was positive going from right to left across the body. The Y direction was in the sagittal plane and was positive going from anterior to posterior. The Z direction was the vertical direction and was positive from the ground up. 110 Trunk ’ Shoulder / (Virtual Point) W Top of Pelvis (Virtual Point)* Greater Trochanter Hip (Virtual Point)* Thigh . Knee Center (Virtual Point)* Shank +Z A +X 2nd Metatarsal Ankle Center . / +Y (V1 \ Globgl Coordinate Axis Pomt)* Vertical ground Foot reaction forces (GRV) Horizontal ground reaction forces (GRH) Figure 28. Five segment sagittal plane model to evaluate joint angles and forces and moments of the low back and right ankle, knee, and hip. *Determination of the location of the virtual points is explained in detail on pages 1 1 1-1 12. 111 Several virtual points were created in this model. The virtual points that were created were the ankle center, knee center, thigh center, hip (proximal end of the femur), shoulder, and top of the pelvis. The ankle center was created from the lateral malleolous position data and was defined to be half the ankle width'in the positive X direction from the lateral malleolous. The knee center was defined to be located half the knee width from the lateral epicondyle in the X direction. It was assumed that any outward rotation of the foot or hip would have minimal affect on these locations of the ankle and knee centers and, thus, minimal effect on the calculated angles, forces, and moments. The thigh center was defined to be a point with the same X coordinate position as the anterior mid-thigh, and Y and Z coordinate positions of the lateral mid-thigh. The purpose of creating the thigh center point was to create a reference point that could be used to help define the local coordinate system of the thigh. The hip (end of femur) was defined as a point the same distance as the greater trochanter from the lateral epicondyle, but located in the line created by the knee center and thigh center (Figure 29). Distance in the X and Z direction from the shoulder (acromion process) to the end of the bar were measured via tape measure during each testing session. The virtual shoulder point was then created in the BodyBuilder software using the end of the bar marker’s coordinate positions and adjusting the X and Z coordinate positions by the tape measured distances while assuming that the Y coordinate position was the same as the bar’s. Finally, the top of the pelvis was defined to have the same X coordinate position as the greater trochanter. The Y coordinate position of the top of the pelvis was calculated by multiplying the cosine of the lower back angle by the length of the pelvis (the distance from the greater trochanter marker to the iliac crest marker as measured by the Vicon system during the first static 112 trial) and subtracting this value from the Y coordinate position of the greater trochanter. The Z coordinate position of the top of the pelvis was calculated by multiplying the sine of the lower back angle by the length of the pelvis and adding this value to the Z coordinate position of the greater trochanter. Again, it was assumed that the participants were perpendicular to the global sagittal plane when performing the squat lifts (parallel, box, and partial). Each segment was created by using the reflective markers or virtual points (Figure 28). The foot was defined as the segment that connected the second metatarsal marker and the virtual right ankle center. The shank was the segment between the virtual ankle and knee centers, while the thigh was the segment between the virtual knee center and the virtual hip point. The pelvis was defined as the segment between the greater trochanter and the virtual top of the pelvis point. Finally, the trunk was the segment from the virtual top of the pelvis point to the virtual shoulder point. Local coordinate axes were defined on each segment to determine joint angles. The BodyBuilder software used Euler angle equations (which determine how much rotation about the X,Y, and Z axes, respectively, must occur for the two sets of axes to be aligned) to assess the angles between segments. Rotations about the X axis (which would represent rotations in the sagittal plane) were evaluated. An example of the local coordinate axes for the foot and shank are provided in Figure 30. The lower back angle was calculated by comparing the local axis of the trunk to the global axes (Figure 31). 113 Greater Trochanter I W. n e C m. h T. Lateral Epicondyle of the F emur ive markers. flect in comparison to re Figure 29. Virtual points (knee center and hip) 114 The static trials were used to determine angle Offsets for the workout trials (i.e., calibrate the angle measurements). For example, the static ankle angle, as measured by the BodyBuilder program, would be subtracted from 90 degrees and this difference would then be added to all ankle angle measurements during the workout repetition evaluation (Appendix E). The static knee angle was subtracted from 180 degrees to determine the knee offset (Figure 32) while the static trunk angle was subtracted from 90 degrees to determine the lower back offset (Figure 31). Lower Local . d' t portion :OSZJIHE: Local of shank Z y coordinate the shank system for the foot X Y Z X Ankle Y \V center FOOt 2"d Metatarsal head Figure 30. Local coordinate systems of the foot and shank. 115 Angle Offset ‘1 — 2‘.‘ I"; ‘2. r‘ "'1." ' .I~‘._ . ‘ .,”. ._\{.~:_.’}.J.cx.& .n.» ‘ '_ .4 . - , l c 4 T '. u Actual Measured Static Lower Back Angle Assumed 90 Degree Angle during Static Trial Figure 31. Determination of lower back angle offset. 116 ”i Knee Angle Offset Measured Static Knee Angle Actual Measured Static .. Ankle Angle Assumed .. l. g 180 Deg.Tee “W"?t' Knee Angle Figure 32. Determination of knee angle offset. 117 A quasi-static analysis of forces and moments was performed. Ground reaction forces from a force platform were used in conjunction with estimated segment masses to determine static equilibrium at each recorded time point in the lifts. The mass and center of mass of each lower extremity segment were estimated using Dempster’s data (Robertson et al., 2004) (Table 7). The BodyBuilder software was used to calculate the forces and moments at the ankle, knee, and hip (Appendix E). However, calculations also were performed in Excel (Microsoft, Redmond, WA) for two trials (the box workout of participant 5 and parallel workout of participant 10) and for all lower back forces and moments. Comparisons of Excel calculated moments and BodyBuilder calculated moments were performed to verify that the same values were produced (Appendix E). Figures 33-37 illustrate how the forces and moments were calculated in Excel. All forces and moments were normalized to body weight to try to account for variation in these variables due to body weight alone (Moisio et al., 2003; Winter, 1991). Table 7 Denyster ’s Body Segment Parameters (as found in Robertson et al., 2004) Segment Segment Mass/Body Mass Location of Center of Mass/Segment Length from Distal End Foot .0145 .500 Shank .0465 .567 Thigh .100 .567 Pelvis .142 .895 118 The knee moment was adjusted to account for the changing length of the distance between the markers of the shank. This distance changed due to: (a) skin and clothing movement and (b) markers not being exactly at the center of rotation of the knee. The length of the shank, as measured by the Vicon system during the first static trial of session three, was considered to be the fixed length of the shank for each participant. The following formula was then used to account for the changing length of the shank: fixed length of shank k) current length of shan adjusted knee moment = original knee moment( Using the session three length as the fixed length also then accounted for differences in shank length between sessions due to marker placement. The hip moment did not need this adjustment because the virtual hip point was used as the end of the femur instead of the greater trochanter. However, the femur length as measured in session three was used for the remaining two sessions for the same reason that the shank length from session three was used. The lower back forces and moments were adjusted to account for the left leg. It was assumed that the horizontal and vertical forces and moment created by the left leg would be equal to that of the right leg. Thus the hip reaction forces and moments were, doubled (Figures 36-37). 119 l RAH fl RAC [MA I I -< J M“! : COMF ' -------- ‘Ill / ll/IAV MGH FWI GRH GRV Z I '- x—V—J MT MGV COP GRH=Horizontal Ground Reaction Force GR V=Vertical Ground Reaction Force COP=Center of Pressure of the Foot on the Force Platform MT =2nd Metatarsal Head COMF=Center of Mass of the Foot F W=F oot Weight MA=Reaction Moment at the Ankle RAH= Horizontal Reaction Force at the Ankle Y MGH =Moment Arm for GRH MG V=Moment Arm for GRV MAH= Moment Arm for RAH MA V=Moment Arm for RAV F h =Forces in the Horizontal Direction F v=Forces in the Vertical Direction BM=Body Mass RAC=Right Ankle Center RA V=Vertical Reaction Force at the Ankle (Counterclockwise Moments Assigned Positive Value and Summed Around COMF) m FVPEBMX.014SX9.81 E5 MAH = RACZ — COMFZ MAV = RACY — COMFY MGH = COMFZ — MTZ MGV = copy - 60er GRH-RAH=0 GRV-FW-RAV=0 2Fh=0 2Fv=0 RAH = GRH RAV = GRV - FW ZM=0 GRVXMGV+RAVXMAV-GRHXMGH—RAHXMAH+MA=0 MA = —GRVXMGV—RAVXMAV+GRHXMGH+RAHXMAH Figure 33. Quasi-static model of the foot to calculate ankle reaction forces and moments for all squats. 120 RKH I I I I : > MKH I I Z I I I I RAH I j Y I RAH=Horizontal Reaction Force MKH= Moment Arm for RKH at the Ankle MK V=Moment Arm for RKV RA V=Vertical Reaction Force MC V=Moment Arm for SW at the Ankle BM=Body Mass MA=Ankle Reaction Moment F h =Forces in the Horizontal Direction RAC=Right Ankle Center F v=F orces in the Vertical Direction C OMS=Center of Mass of the Shank RKC=Right Knee Center S W=Shank Weight MK=Knee Reaction Moment RKH=Horizontal Reaction Force RKV=Vertical Reaction Force at the Knee at the Knee (Counterclockwise Moments Assigned Positive Value and Summed Around RAC) m SW = BM x .0465 x 9.818—2 MAV = RACY — RKCY 2Fh= 0 RAH-RKH = 0 RKH = RAH ZFv=0 RAV-SW—RKV=0 RKV=RAV—SW 2M=0 -(RKV XMKV+SW XMCV+RKH XMKH) XSLC/SL+MA —MK = 0 MK = MA — (RKV x MKV+SW X MCV+RKH XMKH) XSLC/SL SL=Current Shank Length SLC=Fixed (Constant) Shank Length Figure 34. Quasi-static model of the shank to calculate knee reaction forces and moments for all squats. 121 V RKC Y RKH RKH= Horizontal Reaction Force MHH= Moment Arm for RHH at the Knee MHV=Moment Arm for RHV RKV=Vertical Reaction Force MC V=Moment Arm for TW at the Knee BM=Body Mass MK=Knee Reaction Moment F h =Forces in the Horizontal Direction RKC=Right Knee Center F v=F orces in the Vertical Direction COMT=Center of Mass of the Thigh RH=Right Hip T W=Thigh Weight MH=Hip Reaction Moment RHH=Horizontal Reaction Force RH V=Vertical Reaction Force at the Hip at the Hip (Counterclockwise Moments Assigned Positive Value and Surnmed Around RKC) TW = BM x .100 x 9.81;"; MHH = RHZ -— RKCZ MCV = comp - RKCy RKH — RHH = 0 RHH = RKH RKV-TW—RHV=O RHV=RKV—TW MMM 3 ~11 ; " II 1: RHVXMHV+TWXMCV—RHHXMHH+MK—MH=0 MH= RHVXMHV—TWXMCV+RHHXMHH+MK Figure 35. Quasi-static model of the thigh to calculate hip reaction forces and moments for all squats. 122 RLBH Z Y RHH=Horizontal Reaction Force MLBH=Moment Arm for RLBH at the RGTR (Transposed From Hip) MLB V=Moment Arm for RLBV RH V=Vertical Reaction Force MC V=Moment Arm for PW at the RGTR (Transposed From Hip) BM=Body Mass MH=Hip Reaction Moment F h =Forces in the Horizontal Direction RGTR=Right Greater Trochanter F v=Forces in the Vertical Direction C OMP=Center of Mass of Pelvis PT=TOp of Pelvis RLBH=Horizontal Reaction PW=Pelvis Weight Force at the Low Back MLB=Low Back Reaction RLBH=Vertical Reaction Moment Force at the Low Back (Counterclockwise Moments Assigned Positive Value and Surnmed Around RGTR) m PW = BM x .142 x 9.818—2 MLBH = PTZ - RGTRZ MLBV = RGTRY — Pry MCV = RGTRY — COMPY XFh = 0 ZRHH - RLBH = 0 RLBH = ZRHH 2Fv=0 2RHV—PW—RLBV=0 RLBV=2RHV—PW 2M = 0 (RLBV X MLBV + PW X MCV + RLBH X MLBH) — MLB + ZMH = 0 MLB = RLBV X MLBV + PW X MCV + RLBH X MLBH + ZMH Figure 3 6. Quasi-static model of the pelvis to calculate low back reaction forces and moments for the parallel, partial, and Box2 squats. Box2=Instant the participant left the box. 123 \ n A - I - - - - RGTR M}? SRH=Horizontal Seat Reaction Force SR V=Vertical Seat Reaction Force C OP=Center of Pressure RHH=Horizontal Reaction Force at the RGTR (Transposed From Hip) RHV=Vertical Reaction Force at the RGTR (Transposed From Hip) MH=Hip Reaction Moment R GTR=Right Greater Trochanter RLBH=Horizontal Reaction Force at the Low Back C 0MP=Center of Mass of the Pelvis BM=Body Mass RLBH MS V=Moment arm of SRV MLBH=Moment Arm for RLBH MLB V=Moment Arm for RLBV MR V=Moment Arm for RHV MRH=Moment Arm for RHH Fh =Forces in the Horizontal Direction F v=Forces in the Vertical Direction PT=Top of Pelvis P W=Pelvis Weight MLB=Low Back Reaction Moment RLB V=Vertical Reaction Force at the Low Back (Counterclockwise Moments Assigned Positive Value and Surnmed Around COMP) PW = BM x .142 x 9.8153, MLBV = COMPY - Pry MSV = copy — COMPY ZFh=0 2RHH+MSH—RLBH=0 ZFv=o 2RHV+MSV—PW—RLBV=O ZM=O MLB = RLBV X MLBV + RHV X MRV X MSV +SRH X MRH + MLBH = PTZ — COMPZ MRV = RGTRY — COMPY RLBH = ZRHH + MSH RLBV = ZRHV + MSV — PW + RLBH X MLBH + RHH X MRH + SRV ZMH Figure 3 7. Quasi-static model of the pelvis to calculate low back reaction forces and moments for the Box] squat. Box1=Instant participant started to move forward while seated on the box. 124 It was determined to evaluate the box squat at two time points: (a) when the participants were seated on the box (Boxl) at the instant they were starting to move forward (i.e., start of concentric phase) and (b) the instant the participants left the box (Box2) during the concentric phase. The reason for the additional time frame reference was that the lower extremity joints (ankle, knee, and hip) were partially unloaded while in the Boxl condition which were biomechanically different than the parallel or partial squats. The Box2 position allowed for some determination if the forces and moments were similar throughout the unsupported portion of the lift. The following protocol was used to analyze the data: 1. Analysis of the different lifts indicated that the middle repetitions were more consistent. Therefore, repetitions three through nine were evaluated for each participant and the average of these seven repetitions was used to represent each participant’s performance. The first set was used for analysis as long as repetitions three through nine were able to be evaluated. If the first set could not be evaluated using the BodyBuilder software due to marker recognition problems, but all makers were present, the set was evaluated in Excel and the average of the seven lifts was used to represent the performance. This method was used for the box squat performance of participant #5 and the parallel squat performance of participant #10. If markers were missing and all seven repetitions could not be evaluated either using the BodyBuilder software or Excel, then the second set was used. This method was used for the parallel squat performance of participant #11. 125 5. Participant #14’s parallel squat performance did not have any sets that allowed analysis for all seven repetitions and so he was removed from the joint angle, force, and moment evaluations. Repeated measures MANOVAs were used to determine if the angles, forces, and moments were statistically different at the joints during the different workout sessions. An alpha level of .05 was the criteria for statistical significance in all cases. If the MANOVAs were significant, univariate repeated measure ANOVAs were performed with an alpha level set at .05 due to the significant MANOVA (Rencher, 1995). Vertec This evaluation provided an analysis of participants’ ability to generate maximal power. The maximum vertical jump height (best of three trials) obtained at each testing time (pre-, 15 minutes post, and 3 hours post-workout) was used for analysis. The two post-workout values had the pre-workout value subtracted from them and these differences were compared. A 2 X 3 (post-testing times X workout condition) ANOVA with repeated measure on both variables was used to evaluate if there were any differences. Bosco Jump Test Relative mean power was evaluated. The formula for relative mean power is: W: (g* T(60)*60)/(4*n(60)*(60-T (60)) where g is the gravitational constant, T (60) is the total flight time for the full 60 seconds, and n is the number of jumps that occurred during the full 60 seconds. A program written in MATLAB (The Mathworks, Inc., Natick, MA) was used to determine relative mean 126 power. Three participants each had a single step off of the force platform to catch their balance during one of their Bosco jump performances. These steps were identified in their data and were not counted as a jump nor as part of the flight time. Another participant did not land on the force platform at the end of one of his jumps. This participant repeated the jump test on another day. A repeated measures ANOVA was used to determine if there were significant differences between the three workout conditions and the reference test. Borg Scale RPEs were compared using a repeated measure ANOVA. Data Management All motion analysis, force platform, and EMG data were stored on a Vicon computer. The Bosco jump data were stored on a second computer. Additionally, the EMG data were also stored on a separate computer. All EMG, force plate, and kinematic data were stored under coded file names that could not be linked to the participants without a key. The key that matched computer data with each participant was stored in a locked file cabinet. Upon completion of the dissertation, the key will be destroyed so that the data cannot be linked to the participants. Digital videos of participants who have given consent for their use in instructional settings and presentations were copied for such purposes. Only the secondary investigator and the dissertation committee members have access to the data. 127 CHAPTER 4 RESULTS This chapter includes the characteristics of the participants and the results of the data corresponding to research questions in this study. The main focus of the first research question was to compare joint angles of the ankle and knee, and the orientation of the lower back at the lowest point of descent when participants performed parallel, box and partial squats. The second research question investigated how the forces and moments differed at the lowest point of descent in the three squat lifts. The third research question focused on the differences in muscle activity during the lifts and the fourth research question evaluated the relationship between the forces and moments and muscle activity. The purpose of the fifth research question was to evaluate fatigue after workouts. The sixth research question explored the participants’ perceived effort during ' the workouts and the seventh research question evaluated the relationships of the perceived efforts and the amount of fatigue. Participants’ Characteristics The characteristics of the participants are presented in Table 8. Nineteen athletes volunteered for this study. One participant chose to not complete the study due to conflicting commitments. Additionally, one participant was removed from analysis due to complications during his data collection. These complications included: (a) malfunction of the motion analysis equipment that caused there to be greater than three minutes between sets during one testing session and caused a repeat of a set on another session; (b) unusable EMG data; and (c) completion of a testing session after the first 128 week of football practice. Thus, data for 17 participants are reported. These 17 participants consisted of 14 high school athletes and 3 college students (two freshmen and one sophomore). All high school athletes were at least in their sophomore year, were cmrently weight training, and had a minimum of one year experience weight training and six months experience performing both parallel and box squats. The college students were expected to meet the same criteria and, in addition, were also expected to have been lifting at least twice a week for six months prior to participating in this study. All were currently free from orthopedic injuries; in particular, injuries to the lower back and lower extremities. The participants ranged in age from 15 to 20 years and ranged in experience performing parallel and box squats from six months to six years. 129 Table 8 Characteristics of Participants (N =1 7) Characteristic MeaniSD Age (years) 16.8:hl .4 Box Squatting Experience (years) 2.4i1.8 Parallel Squatting Experience (years) 2.4:I:1.7 Weight (kg) 83.01162 Height (cm) 179.1:I:6.7 Sitting Height (cm) 94.1:t3.4 Foot Length (cm) 27.53:] .4 Ankle Width (cm) 7.4i.4 Shank Length (cm) 42.2i2.3 Knee Width (cm) 10.1:t1.0 Femur Length (cm) 44.2:t3.7 Bi-iliac Breadth (cm) 29.1i2.7 Trunk Length (cm) 36.2iZ.7 Bi-acromion Breadth (cm) 41.6i2.0 130 Research Questions RQI. How do the joint angles of the ankle and knee, and orientation of the lower back, at the lowest point of descent, differ among the three squat lifts (parallel, box, and partial squat) ? The joint angle data were evaluated for normality and for outliers. None of the variables were found to have excessive kurtosis or skewness (kurtosis or skewness score/standard error >30) and no outliers (z scores <3.0) were identified. Means and standard deviations for the joint angles of the ankle and knee, and orientation of the lower back are illustrated in Figure 38. A repeated measures MANOVA was first performed summing all three joint angles into a single dependent variable. Table 9 provides the results of the repeated measures MANOVA. Subsequent univariate repeated measures AN OVAs were performed for the ankle, knee, and lower back angles, respectively due to the MANOVA being significant (p<.01). Each of these univariate ANOVAs were performed with an alpha level of .05 (Rencher, 1995). The assumption of sphericity was upheld for the knee angle (p=.07) and lower back angle (p=.l l), but not for the ankle angle (p=.03). Greenhouse-Geiser adjustments were used on the ankle ANOVA due to sphericity assumption not being upheld. Table 10 provides the results of the three AN OVAs. Tukey post-hoc comparisons were performed to determine which of the three squat lifts resulted in statistically different values at the lowest point of descent. Table 11 provides the results of the post-hoc tests. 131 120 * *Ill .2 97.7 * 6.1 (5-1) 89-1 100 i: (v) T (55) 81.5 79.0 # (9.87) (4.5) ** 72.2 ** 66.1 73 .6 (7.4) I 68.4 . 9.64 80 (5 0) I (3-1) 67.9 ( ) E 54.7 a I 8” e 60 .2 i” 40 20 0 Ankle Knee Lower Back Joint/Segment IKey: DParallel DBoxl IBox2 IPartialI Figure 38. Means and standard deviations (SDs) of joint angles at the lowest point of descent. N=16. Box1=instant the participant started to move forward while seated on the box. Box2=instant the participant left the box. *=Significantly different than parallel, partial, and Box2 (p<.05). **=Significantly different than parallel and partial (p<.05). #=Significantly different than partial (p<.05). 132 Table 9 Multivariate Analysis of Variance for the Joint Angles at the Lowest Point of Descent (N =1 6) Error Observed Source df df F p Power“ Joint Angle 9 7 27.88 <.01 1.00 * Calculated using alpha =.05 Table 10 Analysis of Variance for the Joint Angles at the Lowest Point of Descent (N =1 6) Observed Source df F p Power“ Joint Angle Ankle 1.995 52.271 <.01 1.00 Knee 3 1 12.046 <.01 1.00 Lower Back 3 87.732 <.01 1.00 * Calculated using alpha =.05 133 Table 11 Tukey Post-hoe Values for Joint Angles (N= 1 6) Comparison 9’ HSD p flkje Parallel/Boxl 12.89 4.12 <.05 Parallel/Partial 1 .78 2.67 >.05 Parallel/30x2 7.48 3 .61 <.05 Boxl/Partial 1 1.12 3.89 <.05 Boxl/Box2 5.41 2.35 <.05 Partial/Box2 5.71 2.77 <.05 mg Parallel/Boxl 21.04 4.79 <.05 Parallel/Partial 16.93 5.01 <.05 Parallel/Box2 25.48 4.99 <.05 Boxl/Partial 4.1 1 4.06 <.05 Boxl/Box2 4.45 2.23 <.05 Partial/Box2 8.55 4.01 <.05 Lower Back Parallel/Boxl 34.86 7.57 <.05 Parallel/Partial 8.01 5.70 <.05 Parallel/Box2 21.78 7.09 <.05 Boxl/Partial 26.85 7.98 <.05 Box 1/Box2 13.09 4.34 <.05 Partial/Box2 13 .76 6.82 <.05 134 RQ2. How do the forces and moments, calculated using a two dimensional model, at the ankle, knee, and hip joints, as well as the forces and moments experienced in the lumbar region, differ among the three squat lifts at the lowest point of descent? Forces. The horizontal and vertical joint forces were evaluated for the ankle joint and lower back. The reason for evaluating only these two sets of forces were: (a) The horizontal reaction forces are the same for each joint in a quasi static model and so evaluating the knee, and hip would be redundant. (b) The vertical reaction forces of the ankle, knee, and hip only differ by the weight of each limb. (c) The lower back, however, has additional forces imposed upon it by the box and thus the horizontal and vertical forces would exhibit a different result than the pattern exhibited by the ankle, knee, and hip. The force data were evaluated for normality and outliers. The horizontal reaction force during the seated box condition was found to have excessive kurtosis (kurtosis score/standard error>3.0). All other data were found to be normal and no outliers (2 >30) were identified. It was assumed that the MANOVA that was to be performed would be robust enough to compensate for the non-normal data. Means and standard deviations are reported in Figures 39-40. A repeated measure MANOVA was performed on the horizontal and vertical force data for the ankle and lower back. Results are displayed in Table 12. Univariate ANOVAs were then performed to evaluate the specific differences in the ankle and lower back data due to the MANOVA being significant (p<.01). The assumption of sphericity was not upheld for the ankle horizontal forces (p=.02), the ankle vertical forces (p=.02), nor the lower back horizontal forces (p<.01), but was upheld for the lower back vertical forces (p=.2l). Greenhouse Geisser adjustments were used on the three sets of data that had the sphericity violation. Results 135 are provided in Table 13. Tukey post-hoc comparisons were performed to determine which of the different workout conditions were statistically different. Tables 14-15 provide the results of the post-hoc tests. Table 12 Multivariate Analysis of Variance for the Horizontal and Vertical Forces of the Ankle and Lower Back at the Lowest Point of Descent (N=16) Error Observed Source df df F p Power“ Forces 12 4 166.725 <.01 1.00 * Calculated using alpha =.05 Table 13 Analysis of Variance for the Ankle and Lower Back Reaction Force Data at the Lowest Point of Descent (N =1 6) Observed _S ource df F p Power" M Horizontal 2.005 32.380 <.01 1.00 Vertical 1.901 564.819 <.01 1.00 LOvver Back Horizontal 1.809 89.967 <.Ol 1.00 Vertical 3 38.230 <.01 1.00 W Calculated using alpha =.05 136 ** 1.70 **++ (.83) .18 (.41) -1.58 (.27) (.53) .12 (46) (.23) .21 (.16) Ankle Lower Back Joint/Segment Key: DParallel DBox 1 IBox 2 I Partial Figure 39. Means and standard deviations (SDs) of horizontal forces normalized to body weight at the lowest point of descent. N=16. Positive value is in the anterior direction. Box1=instant the participant started to move forward while seated on the box. Box2=instant the participant left the box. *=Significantly different than parallel, partial, and Box2 (p<.05). **=Significantly different than parallel and partial (p<.05). H=Significantly different than boxl (p<.05). 137 30 20.53 (3.36) 19.64 25 (2.93) *4! 15.00 (31;; (2.28) I 20 12.35 (1.62) ** 11.96 10.24 “-40 15 leg (1.60) 10 Ankle Lower Back Joint/Segment Key: DParallel 080x 1 I Box 2 I Partial Figure 40. Means and standard deviations (SDs) of vertical forces normalized to body weight at the lowest point of descent. N=16. Positive value is in the downward direction. Box1= instant the participant started to move forward while seated on the box. Box2=instant the participant left the box. *=Significantly different than parallel, partial, and Box2 (p<.05). **=Significantly different than parallel and partial (p<.05). 138 Table 14 Tukgy Post-hoe Values for Ankle Joint Reaction Forces flV =1 6) Comparison 11” HSD p Horizontal Parallel/Boxl .06 .23 >05 Parallel/Partial .09 . 1 7 >05 Parallel/Box2 .76 .33 <.05 Boxl/Partial .06 .18 >05 Boxl/Box2 .70 .33 <.05 Partial/Box2 .67 .24 <.05 Xe—rtiLal. Parallel/Boxl 1 1.62 1.20 <.05 Parallel/Partial .39 .72 >05 Parallel/Box2 2.1 1 .70 <.05 Boxl/Partial l 1.22 1.12 <.05 Boxl/Box2 9.50 1.15 <.05 Partial/Box2 1 .72 .49 <.05 Table 15 Tukey Post-hoe Values for Low Back Reaction Forces (N =1 6) Comparison SI’ HSD p Horizontal Parallel/Boxl 1.82 .53 <.05 Parallel/Partial .18 .34 >05 F Parallel/Box2 l .46 .65 <.05 Boxl/Partial 2.00 .53 <.05 Boxl/Box2 3.28 .83 <.05 ' Partial/Box2 1 .28 .48 <.05 left—iced Parallel/Boxl 5.52 1.89 <.05 Parallel/Partial 1 .03 1.46 >.05 Parallel/Box2 4.77 2.19 <.05 Boxl/Partial 4.49 1.58 <.05 Boxl/Box2 .75 1.50 >.05 Partial/Box2 3 .73 2.15 <.05 Moments. The joint moment data were evaluated for normality and for outliers. The knee moments during Boxl were found to have excessive kurtosis and skewness (kurtosis score/standard error>3.0, skewness score/standard error>3.0) while the Box2 hip moments had excessive kurtosis. A single outlier (2 =3.05) was identified in the knee 140 moment seated box condition. The outlier was included in the statistical analysis because there was nothing noted during testing that would justify removal. It was assumed that the MANOVA that was to be performed would be robust enough to compensate for the non-normal data. Means and standard deviations for the joint moments of the ankle, knee, hip, and lower back are illustrated in Figure 41. A repeated measures MAN OVA was first performed for all joint moments. Results of the repeated measures MANOVA are reported in Table 16. Univariate repeated measures ANOVAs were performed for the ankle, knee, hip, and lower back moments, respectively, due to the MANOVA being statistically significant (p<.01). The assumption of sphericity was upheld for the ankle moment (p=.36), hip moment (p=.46), and the lower back moment (p=.32) but not the knee moment (p=.01). Greenhouse Geisser adjustments were used for the knee moment evaluations. Table 17 provides the results of the four ANOVAs. Tukey post-hoc comparisons were performed to determine which of the different workout conditions were statistically different. Table 18 provides the results of the post-hoc tests. 141 .335 3:88 55 scenes banneEemmmunn .333 mean nee 3:28 es: sesame baseman“: .Govs use nee .Eeee Ended 55 sesame baseman”... .xop 2: a2 Eamomtwm one ESmEHNxom .xon 05 :0 833 0:23 Eadie.“ o>oE 3 note? 283093 2.: ESmEHCBm douoofio 339628858 E0852 82? o>Emom .EHZ .Eoomov mo “Son “832 05 8 35:88 E830 €99 mcoaagon 2893 use 2862 . 3 3me _ aga- Nxem- came Enema “so: EoEwombfiea xomm 8304 BE 8qu Midas .. or $03 Semi Goo mm.m- ANY; ..Nhgmi NON- T m- 3m. :3 r. as 83 8a. N3- - a- ...... .— _ a3 :3 as - m- .. OS. 3.- an. A . - N- N e3. ...... a w no .— r Ten 4 .w o .. Chg AR: 63 . 8.- . _ . e H : ... .. ... . 85 7mg i m MVH a v0.— nn :; 142 Table 16 Multivariate Analysis of Variance for the Joint Moments at the Lowest Point of Descent W =1 6) Error Observed Source df df F p Power“ Joint 12 4 50.381 <.01 1.00 Moments * Calculated using alpha =.05 Table 17 Analysis of Variance for the Joint Moments at the Lowest Point of Descent (N =1 6) Observed Source df F p Power“ Joint Moment Ankle 3 106.324 <.01 1.00 Knee 1.919 95.195 <.01 1.00 Hip 3 154.972 <.01 1.00 Lower Back 3 47.763 <.01 1.00 * Calculated using alpha =.05 143 Table 18 Tukey Post-hoe Values for Joint Moments (IV =1 6) Comparison lI’ HSD p _A£k_l§ Parallel/Boxl 1.23 .24 <.05 Parallel/Partial .05 .18 >05 Parallel/Box2 .63 .27 <.05 Boxl/Partial 1.18 .25 <.05 Boxl/Box2 .60 .20 <.05 Partial/Box2 .63 .22 <.05 Kn_e_§ Parallel/Boxl 1.57 .41 <.05 Parallel/Partial .21 . 1 8 <.05 Parallel/Box2 .23 .27 >05 Boxl/Partial 1.36 .31 <.05 Boxl/Box2 1.34 .35 <.05 Partial/Box2 .01 .22 >05 144 Table 18 Continued Comparison 5” HSD p Hip Parallel/Boxl 3.15 .47 <.05 Parallel/Partial .36 .32 <.05 Parallel/Box2 1 .17 .49 <.05 Boxl/Partial 2.78 .51 <.05 Boxl/Box2 1.98 .50 <.05 Partial/Box2 .81 .45 <.05 Lower Back Parallel/Boxl 3.83 .79 <.05 Parallel/Partial .37 .49 >05 Parallel/Box2 1 .24 .82 <.05 Boxl/Partial 3.46 .84 <.05 Boxl/Box2 2.59 .92 <.05 Partial/Box2 .87 .83 <.05 145 RQ3. How does recruitment of the vastus lateralis, rectusfemoris, biceps femoris, gluteus maximus, gastrocnemius, and erector spinae muscles differ among the three squatting lifts (parallel, box, and partial)? One participant’s EMG data was removed due to the data being collected at 100 Hz instead of 1000 Hz. Thus, data from 16 subjects were analyzed. The amplitude and duration of the EMG data were evaluated for differences in sequencing of muscle activity and then analyzed using two methods: (a) as a percent of total muscle activity during the lift and (b) as a value normalized to a reference test. Muscle sequencing. Figure 42 illustrates the muscle activity during a typical parallel squat and box squat respectively. The partial squat activity mirrored the parallel squat activity. Thus, the partial squat was not represented in Figure 42 and it was assumed that it would have the same amplitude differences as the parallel squat when compared to the box squat. It is evident from these figures that there were differences in the activity patterns of the muscles during the box squat compared to the parallel squat. The box squat had bursts of muscle activity at the beginning of the eccentric phase followed by a decrease in activity while the participant was sitting on the box prior to the start of the concentric phase. The concentric phase was initiated and then the electrical activity of all six evaluated muscles increased as the participants left the box. During a parallel squat, the muscle activity increased as the participant descended and reached it greatest levels during the concentric phase. The muscle activity decreased as the participants returned to the starting position. 146 (a) (b) Figure 42. Typical rectified EMG pattern for single repetition of (a) parallel and (b) box squat. E = Start of the eccentric phase; C = Start of the concentric phase; F= Finish of repetition. 1 = Rectus femoris; 2 = Vastus lateralis; 3 = Gastrocnemius; 4 = Biceps Femoris; 5 = Gluteus maximus; 6 = Erector spinae. 147 Total muscle activity. Total muscle activity was determined by integrating the muscle activity during each lift and summing the values of the six muscles. This was performed for the eccentric and concentric phases of the lift respectively. The EMG data were first evaluated for outliers. Outliers were identified in the partial squat gastrocnemius data of participant 18 (F325) and parallel and box squat gluteus maximus data of participant 15 (z=3.50, 3.33, respectively). The outliers were not removed because there was nothing specific noted during testing that would lead to the removal of these data. However, if the removal of the outliers had an effect on the statistical evaluation, both sets (with and without the outliers) of data were reported. The EMG data were then evaluated for normality. EMG data for the gluteus maximus during the parallel squat; gluteus maximus and gastrocnemius during the partial squat; and gluteus maximus during the box squat were found to have excessive kurtosis and/or skewness (kurtosis score/standard error>3.0, skewness score/standard error>3.0). It was assumed that the planned ANOVAs would be robust enough to account for the non-normal data and so parametric statistics were still used. A repeated measures MANOVA was not performed on the total muscle activity data (as was done with the angle, force, and moment data) because the dependent variables were linearly dependent upon each other. The EMG data were then evaluated to determine if the order in which the workouts were performed had any effect on the EMG activity. A 2 X 3 (eccentric/concentric X session) ANOVA with repeated measures on both variables was performed for each muscle group. The assumption of sphericity was not upheld for the gastrocnemius and the erector spinae, nor the interaction effect of the rectus femoris and 148 erector spinae. There was not a significant effect (p<.008) for session nor were there any significant (p<.008) interaction effects. Table 19 provides the results for the ANOVAs. Thus the data were evaluated without accounting for order of workouts. Means and standard deviations for the EMG data are illustrated in Figures 43-46. A 2 X 3 (eccentric/concentric X workout condition) ANOVA with repeated measures on both variables was performed for each muscle group. The assumption of sphericity was not upheld for the vastus lateralis (p=.02) and gastrocnemius (p<.01). Greenhouse-Geiser adjustments were used on these two ANOVA analyses due to the sphericity assumption not being upheld. Table 20 provides the results of the six AN OVAs. Only the rectus femoris had a significant effect for workout condition (p<.001) while the biceps femoris had a significant interaction effect (p<.001) in addition to a significant workout effect (p=.004). However, the gluteus maximus had significant workout effect and interaction effect (p=.002 and p=.001, respectively) when the outliers were removed. Tukey post-hoc tests were performed on the combined eccentric and concentric EMG data of the rectus femoris because there was not a significant interaction effect between the eccentric/concentric condition and the workout conditions. Tukey post-hoc tests were performed on the eccentric and concentric portions of the biceps femoris data and the gluteus maximus data with the outliers removed due to the significant interaction effect. Table 21 provides the results of the post-hoc tests. 149 Table 19 Analysis of Variance for the Session EMG Data as a Percent of Total Muscle Activity (N =1 6) Observed Source df F p Power“ Rectus Femoris Eccen/Con (EC) 1 70.852 <.001 1.00 Session (S) 2 1.130 .34 .230 EC X S 1.322 3.532 .07 .489 Vastus Lateralis Eccen/Con (EC) 1 .823 .38 .136 Session (S) 2 1.757 .19 .339 EC X S 2 1.363 .27 .270 Gastrocnemius Eccen/Con (EC) 1 3.214 .09 .389 Session (S) 1.076 1.945 .18 .371 EC X S 2 .288 .75 .091 Biceps Femoris Eccen/Con (EC) 1 23.963 <.001 .995 Session (S) 2 1.271 .30 .254 EC X S 2 .264 .77 .088 Gluteus Maximus Eccen/Con (EC) 1 47.152 <.001 1.00 Session (S) 2 .323 .73 .097 EC X S 2 .76 .48 .167 Erector Spinae Eccen/Con (EC) 1 5.328 .04 .579 Session (S) ' 1.306 1.753 .20 .269 EC X S 1.350 2.102 .16 .320 * Calculated using alpha=.05 150 .Govs Rena one 3:88 one sesame baseman”: .Enz ABS—«5.... 65 E 358.2 20:58 538w 28:8 :38 mo :5on a 3 53:8 28:8 05:88 we $93 mcocmgow 23.8% 98 2802 .3. 3:me 9:80 o_9m=2\o_em=2 _ 3ng xomD Ezfimmfl ”mom _ ea 820 2m 4. we? 3w Dfluvmgm vaO wgavvaun§i mg mmvoew ..W mg” mafififlfidObw o wM/&HOV&J ma wcoev “W $30 o . .- m M . la _ .. . _ a . e . Ed 95.8 1 . 2 m O . . 3 Co .3 mmb v0 5 A . v No m Cumdv m— Qaw mm s A33 3 m . o . o; SOC 36 t cm J # 83¢ E e 8.” % mes . mm m Ewe .. om m E : Gog w 3.2 83: 7 mm M S5 58 $5 W one . seem .. cm H. SEC mm W. 3.3 : a fie .. .. we on: on? r O In 151 AmoVBGoEnEoo 05:00:00 95 05:88va 28 3:88 55 Eobtmw bugoumcwfiu+ $33 388 55 320:6 buéoficmaun .333 3:8 as 6:23 92: Hosanv buééewan: .EHZ .Ammmbmfiw 2: 88m @30th E0238 b338, 28:8 3050 :5on a ma 53:8 28:8 05:88 mo $98 228306 9%:me 23 £822 .3 33va 9.9.0 20322832 _ 13.8m- xomU 6:85am “3M _ 8m 9830 03m 30 mg? 09¢ 042$ 66 98%? m 9.580 w 3 385305 $6534 m3 mtofiu w as w o - W “m l. . 1 O— 3 a Q ans 5.6 h God m m? . . . ‘ $2.3 m; 3: ans aoiomc Ammomw 2 am 33 03 so E - om w Rd 8 m i B Gm: r cm m 8.2 . s 33 32v . mm m 9:: . . .. G” t ., V 5 t S vm . . 2 mm r ow m : om 55 k. 858 m” 83 83v 3% $2: ... 1 3 .M . Sam Smm r Om .lvlifl’ I’VQO‘C I‘ll! 1'-'I‘o'l4lluoi" 152 .GoVB Eta: :8: 8082:: bEwufiEwmmua .AmoVS 383 88 20:88: :05 80.:0Htv EEwocmcwmmH: .2“? $8380 05 8 808808 80:88 Eggs 28:8 139.8 8080: 0 mm 3388 28:8 28:00:00 .8 $93 8828300 8288 :80 8002 H» 088k 153 .880 28320—832 _ 1280m- xomfl 6:08am >0M _ 8W fiofifio 903m mamv «ma? 00¢ 093$ 030 3868.2 m 9.880 w m 88808008 290:5 w: 2.580 w m3 0 1 m .d a _ _ - 2 u. 3 .. w Do sod . and .w 2 3 .. 8%.... ...... . :30 ...... . . om 1 MM. WV 3;: 8.3 :Ww m . 8.2 l mmmw SE 8:3 :30 5.3:. mm w :30 NV: 8.: :3. . m 8: n. 8.2 , cm a 8.3 55 W 8:: 8.8 1 mm m” ...... a” $08 at: 9&5 r ow 3.2 8.; $8 it‘lallill.f' . 4.7.- t . .O‘Oalllnii .AmoVS xop 23 3:88 :9: Echobzu bfimocmcwmmn+ .AmoVS €3.23 98 3:83 52: “scumbag bugomawmmui .EHZ .2332“ 2: soc 8882 22:33 33:8 282: 39 mo 52% a ma 33:8 28:8 3:588 mo G93 mcosfigw 23¢me was 332 .3. 333k 9.20 23:20—93: _ 65.8m- xomD Ezfimmu whom gnaw 93¢sz 03m who ma? 00¢ oafimaw v0.5 mfifififidi w wCOEQ W wQ mfime‘ufionuvy mM/fluofiwxw ma vaOEU W was - : o .. m d - 3 I. — r 3 a 8H5 H A _. v 5.3 . 399 m 23 Amwd cmowo 9: Go 0 o? x 2 9% . Ed :.2 .... mm” w. W as Ed 9.0.3 T om m + was 3.2 m. E; Gwi $03 1 mm w 3.2 5.3 :2 on: m £2 93.8 T om 1 32 EB W vo mm 1 mm m... ..i M. F” 80.3 2:5 83V ow 2.3 2.2 ”Zn ....o‘.'|l‘l an IQ! In ol.‘u9.0.0 -1 a I 1 ¥ 1 } 154 Table 20 Analysis of Variance for the EMG Data as a Percent of Total Muscle Activity (N =1 6) Observed Source df F p Power“ Rectus Femoris Eccen/Con (EC) 1 81.718 <.001 1.00 Workout (W) 2 12.956 <.001 .994 EC X W 2 2.626 .09 .482 Vastus Lateralis Eccen/Con (EC) 1 1.037 .33 .159 Workout (W) 1.393 .979 .36 .204 ECXW 2 .817 .45 .176 Gastrocnemius Eccen/Con (EC) 1 3.228 .09 .391 Workout (W) 1.118 1.405 .26 .209 EC X W 2 4.654 .02 .740 Biceps Femoris Eccen/Con (EC) 1 24.149 <.001 .996 Workout (W) 2 6.575 .004 .880 EC X W 2 14.675 <.001 .998 Gluteus Maximus Eccen/Con (EC) 1 51.940 <.001 1.00 Workout (W) 2 3.783 .03 .645 EC X W 2 10.474 <.001 .980 Gluteus Maximus-Outliers Removed (N =14) Eccen/Con (EC) 1 81.889 <.001 1.00 Workout (W) 2 7.642 .002 .920 EC X W 2 9.597 .001 .967 T=Calculated using alpha=.05 155 Table 20 Continued Observed Source df F p Power“ Erectror Spinae Eccen/Con (EC) 1 6.725 .02 .679 Workout (W) 2 3.942 .03 .664 EC X W 2 3.510 .04 .610 *=Calcualted using alpha=.05 156 Table 21 Tukey Post-hoc for the EMG Data as a Percent of Total Muscle Activity (N =1 6) Comparison 5” HSD p Rectus Femoris Parallel/Box 3.99 2.39 <.05 Parallel/Partial 1.09 1.59 >.05 Partial/Box 5.08 2.37 <.05 Biceps Femoris Eccentric Parallel/Box 1.05 2.16 >.05 Parallel/Partial .93 l .97 >05 Partial/Box .13 l .62 >05 Concentric Parallel/Box 3.48 2.97 <.05 Parallel/Partial .17 2.61 >.05 Partial/Box 3.31 2.55 <.05 G1 uteus Maximus-Outliers Removed (N=14) Eccentric Parallel/Box 1 .23 1.47 >.05 Parallel/Partial 1 .42 1 .63 >05 Partial/Box . 19 1.53 >.05 Concentric Parallel/Box .23 1 .82 >05 Parallel/Partial 2.06 1 .97 <.05 Partial/Box 2.28 1.86 <.05 \ 157 Normalized to reference test. The EMG data were first evaluated for outliers. Outliers were identified in the partial squat gastrocnemius data of participant 18 (z=3.7), parallel squat biceps femoris data of participant 10 (F341), and parallel squat erector spinae data of participant 19 (z=3.06). The outliers were not removed because there was nothing specific noted during testing that would lead to the removal of these data. However, if the removal of the outliers had an effect on the statistical evaluation, both P sets (with and without the outliers) of data were reported. The EMG data were then evaluated for normality. EMG data for the rectus femoris, biceps femoris and erector spinae during the parallel squat; gluteus maximus, gastrocnemius, and erector spinae during the partial squat; and the erector spinae during the box squat were found to have excessive kurtosis and/or skewness (kurtosis score/standard error >3.0, skewness score/standard error). It was assumed that the planned AN OVAs would be robust enough to account for the non-normal data and so parametric statistics were still used. The EMG data were then evaluated to determine if the order that the workouts were performed in had any effect on the EMG activity. A 2 X 3 (eccentric/concentric X session) ANOVA with repeated measures on both variables was performed for each muscle group. The assumption of sphericity was not upheld for the gastrocnemius’ session condition (p<.001). A Greenhouse-Geiser adjustment was used on the gastrocnemius’ ANOVA due to the sphericity assumption not being upheld. There were not any significant effects (p>.008) for session nor any significant interaction effects (p>.008). Table 22 provides the results for the ANOVAs. Thus, the data were evaluated without accounting for order of workouts. 158 Means and standard deviations for the EMG data are illustrated in Figures 47-50. A 2 X 3 (eccentric/concentric X workout condition) ANOVA with repeated measures on both variables was performed for each muscle group. The assumption of sphericity was not upheld for the gastrocnemius nor the bicep femoris data (p<.01). Additionally, sphericity was not upheld on the interaction effect for the bicep femoris data nor the erector spinae data (p<.01 in both cases). Greenhouse-Geiser adjustments were used on these ANOVA analyses due to the sphericity assumption not being upheld. Table 23 provides the results of the six ANOVAs. Tukey post-hoe tests were performed on all significant ANOVAs to determine which specific workout conditions were significantly different. Table 24 provides the results of the Tukey post-hoe tests. 159 Table 22 Analysis of Variance for the EMG Data Normalized to Reference Test Session Check (N =1 6) Observed Source df F p Power“ Rectus Femoris Eccen/Con (EC) 1 2.542 .13 .321 Session (S) 2 .544 .59 .131 EC X S 2 .357 .70 .102 Vastus Lateralis Eccen/Con (EC) 1 147.329 <.001 1.00 Session (S) 2 .827 .45 .178 EC X S 2 .253 .78 .086 Gastrocnemius Eccen/Con (EC) 1 21.055 <.001 .990 Session (S) 1.101 .718 .42 .129 EC X S 2 .149 .86 .071 Biceps Femoris Eccen/Con (EC) 1 53.871 <.001 1.00 Session (S) 2 1.075 .35 .221 EC X S 2 .658 .53 .150 Gluteus Maximus Eccen/Con (EC) 1 36.213 <.001 1.00 Session (S) 2 .166 .85 .073 EC X S 2 .493 .62 .123 Erector Spinae Eccen/Con (EC) 1 14.335, .002 .942 Session (S) 2 .110 .90 .065 EC X S 2 .237 .79 .084 *=Calculated using alpha=.05. 160 05 E 8398 20:58 32 8:80on 9 B32250: .33ch 382: $5508 90 $98 mcoumgow vacuum use 232 N v 3wa :3 SA unwfimow ova HOV W¢E¢é2 m $330 ** . 2 33 mm _ o3 83 .. mm.~ 60$ EN a: N3 asewflomsgflumsz _ Etna- xomn. 6:880 :on 00me web we? 0on 9.58» w m0 m380¢oob $366) m3 9.68» w mg m o A V . . ma. . T _ om. h me. A. Amwv :3 . .. 63 T N ...... :m.v mm. W Avmv DNA AD»; ...... and; Hmé mmé . . T N omA T v W. m. .- m P ....A. T. 0 w T n :59 T w ww.~ .333 3:8 Ba 3:88 as: Beebe baseman”: .0 T2 .Ammmbfia Illloiii ta 3?! i. :Tl-.0lt.l.l"l Tl lilii I 161 00:5:50 0:: 05:00:00 0:0 05:0000 :05, Amo.v3 3:3: 0:: :80. SB: ::0:0w:: 3::00E:w:mn++ .Gove 3:8 2a 6:88 :2: 220.06 :zfiomewau: .m :HZ 00—003: :05: =< 05:58:: 0:033 0:0 £2882 mam? $880.: 0300: :0: EHZ $6305: 0:: 80:: 00580: 0:02:58 :00: 00:0:000: o: 00:20::0: 53:00 200:8 05:88 :0 $98 0:03:30: 0:00:80 0:: 0:002 .23. Bumrm :520200522032 35$ I xom D 320:0: D 0:3: 05 3:30 3m 000 007 004: 009.:m :90 0:86:02 0 €080 w 30 0:66:00: 380:4: 03 90060 w 03 . c :1 3:: Am: T _ ...... AVNQ ...... ANN; . ...... 7 N N 33 . ~:.: 0:: Em: 2:3 .0. ~:.: Wm.” 51 _ E: om. 2.: Am: m 8.: mm: 3:: 0:: T m m .. 83 a: A mm.~ ++ W. .. v w .. ,. m God hm.N T o 162 $33 .2000 :05 0:20:06 :_:§oc::0_0u§ 30.x: E00: 0:0 0:000 :20 0:20.00 20500000": .072 0:00:05 0:: E 00::0:0: 0:02:30: :00: 00:0:0.:0: 0: 00:20:50: 33000 2000:: 05:00:00 .:o 0va 0:2:0300 0:00:80 0:0 0:002 60 0:030: 95:”: 0.00=E0_00=E _ _0_::0ml xomD _0=0:0mD $0M — 0%”: 00:30 0%: 0O 007 004: 00E:m :80 03:30.2 0 00020 w 090 0360:00b0 0:05:01: 0:: 00080 w 03 :3 : _ _ a: : m. . 0 II mm. gm; at Ammg :0: 00.: a: .... :0: 00.: 0: w :~.~ : .2 03 r 0 m No.0 :05: wk. 2.0 W :05 I 0 M :00 .. m. an Aomdv ,. A: 3 mm.m ... :00: .. m: a: .0: 00.: m: 0 E 163 .BHHBEoo 8w 05538 28 0.5580 5:3 AmoVS 3th can xop H85 Hcobtmu bHHaoEHHEmHTT .335 3:88 52: 220% éfifiémufi .qu3 Eng 93 HaasQ 52: eegu Hsfiéfian: .2"? 8338 550 =< $35wa 382w 28 5:8on— msHmm> .3088 388 How EHZ Aflmbwcm 05 €on @9582 $0538 58 082$an oH Hug—«8.5: @338 282: 3.55250 mo $93 mcotagow 93:30. 28 3on .3 953K 6“.» :.v I It 'l.t....-‘t (ISIIIitIIIBPEYI91.15": I-.??l-ti . u-“ii'l¢.i vaA.I9i‘c ...It.o,.,a..l. lit Oi 01.. .0 0 7| . (.00. O 9.86 2935:2932 _ Enam- xomU 6:85;. Sex _ 3N $33.0 3w mamv ma? 002W 286m 6% gain? m €08» w moo maeucoob mafia“; ma 9.580 w a? ... o SW. . mm. . . mm AR; 8 H — . AMMHV an $3 .. H 63 ...... 81 mm. an 33 H v m .H vmé . . o :5 5.: an: an H Hm H w . . . . l.— mH H E: E H 3 H E .Hv , o m mod mo m I. ++ m SE .. w n. Hmé m an m x 3 mm \. mmfl _. E 164 Table 23 Analysis of Variance for the EMG Data Normalized to Reference Test (N =1 6) Observed Source df F p Power" Rectus F emoris Eccen/Con (EC) 1 2.542 .13 .321 Workout (W) 2 22.423 <.001 1.00 EC X W 2 14.014 <.001 .997 [1 Vastus Lateralis Eccen/Con (EC) 1 147.329 <.001 1.00 j Workout (W) 2 25.908 <.001 1.00 1 4' EC X W 2 13.221 <.001 .995 Gastrocnemius Eccen/Con (EC) 1 21.055 <.001 .990 Workout (W) 1.072 1.209 .29 .244 EC X W 2 2.704 .08 .494 Gastrocnemius-Outliers Removed (N=15) Eccen/Con (EC) 1 17.627 .001 .974 Workout (W) 2 6.365 .005 .863 EC X W 2 2.649 .09 .483 Biceps Femoris Eccen/Con (EC) 1 53.871 <.001 1.00 Workout (W) 1.116 20.353 <.001 .993 EC X W 1.343 11.834 .001 .951 *=Calculated using apha=.05. 165 Table 23 Continued Observed Source 4f F p Power" Gluteus Eccen/Con (EC) 1 36.213 <.001 1.00 Maximus Workout (W) 2 8.786 .001 .955 EC X W 2 5.854 .007 .838 Erector Spinae Eccen/Con (EC) 1 14.335 .002 .942 Workout (W) 2 18.157 <.001 1.00 EC x w I 1.268 15.547 <.001 .982 *=Calculated using apha=.05. 166 Table 24 Tukey Post-hoe Values for the EMG Data Normalized to Reference Test (N =1 6) Comparison SP HSD p Rectus Femoris Eccentric Parallel/Box .71 .33 <.05 Parallel/Partial .1 1 .40 >05 Partial/Box .59 .30 <.05 Concentric Parallel/Box .58 .33 <.05 Parallel/Partial .38 .41 >05 Partial/Box .20 .22 >05 Vastus Lateralis Eccentric Parallel/Box .72 .22 <.05 Parallel/Partial .09 .43 >05 Partial/Box .81 .40 <.05 Concentric Parallel/Box .91 .37 <.05 Parallel/Partial .25 .54 >05 Partial/Box .66 .49 <.05 167 Table 24 Continued Comparison W HSD p Gastrocnemius-Eccentric/Concentric Combined Parallel/Box .91 .61 <.05 Parallel/Partial .57 .40 <.05 Partial/Box .34 .56 >05 Biceps F emoris Eccentric Parallel/Box .81 .44 <.05 Parallel/Partial .19 .45 >05 Partial/Box .62 . 16 <.05 Concentric Parallel/Box 1 .97 1.37 <.05 Parallel/Partial .81 1.22 >.05 Partial/Box 1 . 16 .46 <.05 168 Table 24 Continued Comparison SP HSD g Gluteus Maximus Eccentric Parallel/Box .77 .48 <.05 Parallel/Partial .64 1 .37 >05 Partial/Box 1 .41 1 .34 <.05 Concentric Parallel/Box 3.08 2.73 <.05 Parallel/Partial .36 2.21 >.05 Partial/Box 2.72 3.21 >.05 Erector Spinae Eccentric Parallel/Box .64 .24 <.05 Parallel/Partial .03 .43 >05 Partial/Box .61 .38 <.05 Concentric Parallel/Box 196 .57 <.05 Parallel/Partial .57 .62 >05 Partial/Box .39 .44 >05 169 RQ4. Is there a relationship among the electrical activity of selected muscles and the forces and moments experienced at the lowest point of descent? This research question was not answered due to the analysis methods used with the EMG data. The forces and moments were evaluated at a single time point, but the EMG signal was averaged over the course of the eccentric and concentric portions of the lifi. RQ5. How do selected performance parameters (maximum vertical jump and anaerobic endurance as measured by a Bosco jump test) of participants change due to completing workouts of the three different squatting exercises? Maximum vertical jump and Bosco jump data were first evaluated for outliers. No outliers were identified (2 > 3.0). Both sets of data were then evaluated to determine if there was an effect for order of testing. A 2 X 3 (difference from pre-workout X session) ANOVA with repeated measures on both independent variables was performed on the vertical jump data. A repeated measures ANOVA was performed on the Bosco jump data for sessions three through five. The session two data (the unfatigued reference) was not included because it was always performed first and was not randomized with the other sessions. It should be noted, however, one participant did have to repeat his reference test and this was completed after session five. The assumption of sphericity was upheld for both maximum vertical jump (p=.32 session, p=.38 difference X session) and the Bosco jump test (p=.37) ANOVAs. The vertical jump ANOVA was not significant for the session test and the Bosco jump test ANOVA was not signficant so data were analyzed without taking order of testing into account. Tables 25-26 report the ANOVA data of these tests. 170 Table 25 Analysis of Variance for Order Effect of Difference from Pre-workout Vertical Jump (N =1 7) Observed Source df F p Power“ Session (S) 2 .263 .77 .088 Difference 1 4.510 .05 .514 (D) S X D 2 .304 .74 .094 *Calculated at alpha=.05. Table 26 Analysis of Variance for Order Effect quosco Jump Test (N =1 7) Observed Source df F p Power“ Session 2 .180 .837 .075 *Calculated at alpha=.05. 171 Vertical jump test. The data were evaluated for normality. All data were found to be within normal limits of skewness and kurtosis (skewness or kurtosis statistic/standard error scores <3.0). Figure 51 provides a graphic illustration of the means and standard deviations of the post-workout vertical jump data. A 2 X 3 (difference from pre-workout X workout condition) ANOVA with repeated measures on both independent variables was performed on the vertical jump data. The assumption of sphericity was upheld a (p=.82 workout, p=.80 difference X workout condition). Table 27 presents the AN OVA I data for the post workout vertical jumps. EI- 172 0.5 q; 0 .2. '8 o. G) 8 -O.5 2 O .S 1 .“2’. l (.8) j“ *5 -1 8° .2 o g .1 (.7) (.9) 18 (1-1) 23 g -1.5 e I .4 a) 1.2 a (.7) ( ) ,5 _2 l l 1 ** 1 l 1 -2.5 * Vertical jump 15 min Vertical jump 180 min 7 difference difference I Key: DParallel DBox lPartiall Figure 51. Means and standard deviations (SDs) of the decreases in vertical jump height from pre-workout at 15 minutes and 180 minutes post-workout. N=l 7. Values reported in inches due to the Vertec using half inch increment measurements. * The three types of squats as a group were significantly different (p = .05) at Vertical Jump 15 min compared toVertical jump 180 min. *"' Parallel squats when both time points were grouped together were significantly different (p < .05) from box and partial squats. 173 Table 27 Analysis of Variance for Vertical Jump Post-workout (N=17) Observed Source df F p Power“ Workout (W) 2 5.017 .01 777 Difference 1 4.510 .05 .514 (D) W X D 2 2.403 .11 .449 *Calculated at alpha=.05. Tukey post-hoe tests were performed to compare the three workout conditions. Combined data from the 15 minute and 180 minute post-workout testing were analyzed because there was not a significant interaction effect (as shown in Table 27). The difference in vertical jump height after a parallel squat workout was significantly different (p<.05) than after both the box and the partial squat workouts. Table 28 provides the post-hoe results. Table 28 Tukey Post-hoe Values for Vertical Jump Post—workout (VJ I5 and VJ I80 Combined) fl =1 7) Comparison 1V HSD p Parallel/Box .78 .53 <.05 Parallel/Partial .60 .49 <.05 Box/Partial .18 .49 >05 174 Bosco jump test. The data were first evaluated for normality. All data were found to be within normal limits of kurtosis and skewness (kurtosis (or skewness) statistic/standard error scores <3.0). Means and standard deviations for the Bosco jump test are presented in Figure 52. A repeated measures ANOVA was performed. The assumption of sphericity was upheld (p=.620). There were no significant differences between any of the workout sessions. Table 29 presents the AN OVA table for the Bosco data. 7 1 Watts/kg \OOr—*NUJAUIO\\IOO\OO§ OF—‘NWAUIQVOO Reference Parallel Box Partial Figure 52. Means and standard deviations (SDs) comparison of anaerobic endurance as measured with the Bosco jump test. N=17. 175 Table 29 Analysis of Variance for Bosco Jump Test (N =1 7) Observed Source df F p Power" Workout 2 l .966 .1 3 .475 *Calculated at alpha=.05. RQ6. How do participants ’ perceived effort, immediately after bouts of the three diflkrent squat exercises, differ? Ratings of perceived exertion (RPE) for the three squat lifts (box, parallel, and partial) were compared for first set RPE, average RPE for all sets, and post-workout RPE for all 17 participants. All comparisons were similar in value and so only average set RPE was evaluated. The average set RPE was chosen because it would be the easiest to compare to previous studies. The average set RPE values were first evaluated to determine if there was an effect for the order in which the workouts occurred. A repeated measures ANOVA was performed. The assumption of sphericity was upheld (p=.7l). Table 30 provides the ANOVA results. The RPE data were then evaluated without respect to time order due to the insignificant ANOVA test. 176 Table 30 Analysis of Variance for Order of Workout Comparison of Perceived Exertion (N =1 7) Observed Source df F p Power“ Session 2 .240 .79 .084 *Calculated at alpha=.05. 1: NEH A repeated measures ANOVA was then performed to evaluate if the participants perceived that the workouts were of different intensity. Prior to performing the ANOVA, ' the data were evaluated for normality and outliers. All data were found to be within normal limits of kurtosis and skewness (kurtosis (or skewness) statistic/standard error scores <30) and no outliers (z scores <3.0) were identified. Figure 53 provides an illustration of the means and standard deviations of the RPE scores given. The assumption of sphericity was upheld (p=.43). Table 31 provides the results of the ANOVA. Tukey post-hoe tests were performed to determine which of the workout conditions were different. Table 32 provides the results of the Tukey post-hoe tests. Table 31 Analysis of Variance for Workout Condition Comparison of Perceived Exertion (N =1 7) Observed Source df F p Power“ Session 2 39.208 <.01 1.00 *Calculated at alpha=.05. 177 . 6.7 (1.4) 00 4.2 4.9 (1.5) (1.0) Parallel Box Partial Figure 53. Means and standard deviations (SDs) of average set RPE values after the three workout conditions using the modified Borg scale. N=17. * Significantly different than box or partial RPE. (p<.05) Table 32 Tukey Post-hoc Values for Perceived Exertion flV =1 7) Comparison 1V HSD p Parallel/Box 2.49 .68 <.05 Parallel/Partial 1 .84 .87 <.05 Box/Partial .65 .69 >05 \ 178 RQ 7. Is there a relationship between participants ’ perceived eflort and the rate of recovery? Pearson correlations were performed comparing the average of the three workout condition RPE values for each participant to the average of the three workout condition measurements of fatigue: (a) decrease in vertical jump at 15 minutes (VJ 15), (b) decrease in vertical jump at three hours (VJ 180), and (c) the relative power value of the Bosco jump test (Bosco). There were no significant relationships between RPE and any of the measures of fatigue. Table 33 provides the results of the Pearson correlations. Table 33 Pearson Correlations Comparing RPE to Recovery Comparison r p RPENJ 15 .16 .55 RPE/VJ180 -.08 .77 RPE/Bosco .20 .44 179 CHAPTER 5 DISCUSSION This study sought to evaluate the differences in joint position, joint forces and moments, recovery, and perceived exertion among parallel, box, and partial squats. This chapter will first report the steps that were taken to minimize threats to internal and external validity. Second, each research question will be discussed with respect to the results and a summary of the practical benefits of this knowledge will follow. Finally, limitations of this study will be discussed and suggestions for future research will be ' provided. Minimizing Threats to Validity Minimizing Threats to Internal Validity History, testing, instrumentation, experimental mortality, and expectancy were threats to internal validity in this study. Attempts to minimize these threats are discussed in the following paragraphs. Maturation posed little threat to the validity of this study due to the short length of data collection. Statistical regression, selection bias, and selection-maturation interaction did not apply to this study because it was a repeated measures design and, thus, all participants received all treatments. History. The main history threat to this study was the participants’ activities prior to the testing sessions. A brief questionnaire (Appendix B) was given prior to the start of the study. Potential participants that had current health problems (e.g., hernias, mononucleosis), and/or current orthopedic problems (e. g., broken bones, sprained knees/ankles, torn ligaments in the lower extremities, spinal injuries) would have been 180 excluded from the study. No potential participants had any of these health problems and so no participants were excluded. Previous orthopedic and health problems were evaluated on a case by case basis for inclusion and, since all participants had been currently lifting with their school programs, none were excluded from participation. The volunteers that qualified for inclusion were given instructions to refrain from any vigorous activity for 48 hours immediately prior to each testing session to minimize the effects of these activities on the testing results. Vigorous activity was defined to be any weight training of the lower extremity, competitive sport activity, or endurance activity lasting over 20 minutes. A second questionnaire (Appendix B) was given prior to each testing session asking about physical activities performed in the last 48 hours and the amount of sleep that the participants had prior to the testing. The 48 hour restriction on weight training of the lower extremity was strictly enforced, but the 48 hours of no activity over 20 minutes was not. This was due to the fact that it was very difficult to schedule times that were 48 hours apart from other commitments (i.e., school physical education classes and off-season conditioning). It would not have been possible for the majority of participants to complete the study if the 48 hours with less than 20 minutes of activity was strictly enforced. The question about activity was still used and the participants had to explain what the activities were and when they were performed. In general, most participants had at least 24 hours recovery prior to testing and most had 30 minutes or less physical activity the day prior to testing. Participants were also expected to have had six hours of sleep the night prior to testing. This was violated one time as one participant had only five and a half hours of sleep. This participant was still allowed to participate because it would have been 181 another week before he could reschedule and that would have put his testing dates one month apart. Finally, the second questionnaire asked if any injury had occurred recently that would affect their ability to perform the three squat lifts required for this study. One participant reported that he was involved in a minor car accident outside of this study. It was determined that the participant was still able to participate as he had parental permission to continue both his normal training and participation in this study. f Testing. Minimizing the time between the sessions attempted to limit the amount '“ .32-1L '.t I . of possible outside influences on the study. It was attempted to have each session occur a minimum of 48 hours apart and a maximum of two weeks from the previous session. Three participants were not able to fulfill these guidelines. These three participants had three weeks between sessions 2 and 3. However, all of these participants then completed the last three sessions (the three workouts) within the desired guidelines. The longest time it took a participant to complete all five sessions was seven weeks. The shortest time was three weeks. Maturation should have had little effect on the outcomes of this study due to the short time frame in which data collection occurred. Instrumentation and testing error. Instrumentation error posed a threat due to collecting data on multiple occasions. All instruments were calibrated prior to use on each testing day and periodically checked between participants to confirm that measurements were consistent. The greatest problem was the placement of EMG electrodes and reflective markers over multiple testing sessions. The placement of reflective markers was compared to the previous session using the Vicon system and it was expected that the markers would be within .5 cm their original placement. All virtual markers (e.g., femur length) used the distance measured on the first workout condition so 182 that those segments would be the same length. The placement of the EMG electrodes were measured with reference to bony landmarks (e. g., lateral epicondyle of the tibia and greater trochanter) to allow for accurate placement from one testing session to another. Additionally, Henne tattoo dye was used to mark the skin to record the placement of the electrodes and markers that came into direct contact with the skin. Experimental mortality. Mortality in this experiment was participants not FI completing all six sessions. Scheduling the sessions within a limited time frame helped . minimize the mortality of the participants. The number of different workouts was kept to a minimum to help facilitate this goal. One participant did not complete the study due to b other commitments. That participant had completed four sessions prior to choosing to not finish. Expectancy error. Expectancy error was minimized by randomly assigning participants to a preplanned order of performance of the box, parallel, and partial squat to not bias one activity over the others. The goal was to have the number of participants be a multiple of six to have an equal number of participants perform each possible order. Even though this goal was not met, the time evaluation (e. g., session 3 compared to session 4 regardless of workout condition, etc.) only showed an effect for time once (rectus femoris EMG when evaluated as a percentage of total muscle activity). Additionally, helpers were instructed to act the same way for each training protocol and not try to motivate the participant to perform harder for any particular method of squatting. 183 Minimizing Threats to External Validity Multiple treatment interference posed considerable threat to the validity of this study because the repeated training sessions and the effect of one session on the next test results. To minimize this threat, participants were randomly assigned to one of the six possible orders of testing. Furthermore, the number of different experimental conditions was kept to a minimum to limit the amount of strength improvement that occurred with weight training. The use of reflective videography markers also posed a threat to the external validity. Markers shifted during movements due to the skin/clothing not changing position in the same manner as the underlying bony landmarks. To minimize the amount of error caused by markers that were placed on clothing, it was required that the participants wear minimal, tight fitting clothing (no shirt or an “Under Armor” shirt and compression shorts). Research Questions RQI. How do the joint angles of the ankle and knee, and orientation of the lower back, at the lowest point of descent, differ among the three squat lifts (parallel, box, and partial squat)? The majority of joint angle differences were expected due to the design of the experiment (Figure 38). The angle of the ankle was expected to have less dorsiflexion (larger angle) when the participants were sitting on the box when compared to the angle of the ankle at maximum descent in the parallel or partial squat. Of more interest was that there was still less ankle dorsiflexion when coming off of the box (Box2 position) than in the lowest positions of the parallel or partial squat. It was also interesting that 184 there was not a significant difference in ankle angle between the parallel and partial squat. This would indicate that the majority of the participants had reached their maximal ankle flexion by 90 degrees of knee flexion and that the majority of differences in body segment orientation in these lifis occurred at the knee and trunk. The angles of the knee and orientation of the lower back would support this assumption. The knee angle results were as expected except for the significant difference between the partial and seated box squat. It was the goal of this experiment to have these angles similar. The most probable reason for the slightly greater than 90 degree knee angles during the seated box squat was that the knee angle checks were performed with an un-weighted bar or without a bar. Participants practiced a few box squats to get an idea of where their foot placement would be. However, foot placement was not strictly regulated during the box squat like it was during the parallel and partial squats since the box placement regulated the movement. Most likely, most participants had their feet placement slightly farther away from the adjustable box during the actual testing compared to the static trials and this created the slightly larger angle. However, the majority of participants felt that the box height was representative of how they performed box squats in their normal training. The slightly lower than 90 degree knee angle that was observed during the partial squats can primarily be explained by the fact the bungee cord offered minimal resistance and that the participants tended to slightly overshoot the depth, even with verbal instruction of when to start the concentric phase. Future studies would need to regulate the foot placement during the box squat to provide better control the joint angle. A stiffer bungee cord may have provided slightly better knee angle results, but could have had more influence on the squat technique if it actually allowed 185 the participant to slightly unload some of the weight during the eccentric/concentric transition. The lower back angles were as expected. The lower the participant descended, the greater the forward trunk lean. In the box squat, participants tended to rock back on the box which dramatically reduced trunk lean. Determination of the lower back angle should be interpreted cautiously. It was initially intended to determine the rotation of the F' pelvis by using markers on the superior aspect of the iliac crest, anterior superior iliac spine, and sacrum. Unfortunately, these markers tended to be the ones obscured at the lowest point of descent by other body parts, weights on the bar, EMG cables, or spotters. i Furthermore, even though the marker on the superior aspect of the iliac crest was placed on the skin of the participant, it moved considerably as the participant moved, especially if the participant had excessive fat stores around the abdomen. This limited its use as a bony landmark. The sacrum marker also created difficulties. The marker needed to be attached to the top of the participants’ shorts when they were in an upright position. The shorts would then move as the participant descended, making the sacrum movement not representative of the pelvis. Placement of the marker on the skin would have been difficult and would have been pushed in different directions by the shorts of the participant at different stages of the lift. Ideally, a marker would be attached to the skin and a hole would have been created in the back of the shorts to allow for free movement. This was not practical in this study since most participants provided their own shorts and requiring them to cut their shorts may have discouraged participation. These problems are not observed in normal gait analysis which the Vicon system is normally used for because there is not such drastic change in trunk, pelvis, or hip angle during gait. Thus, it 186 was determined to use the end of the bar to create a virtual shoulder point and use the angle between the greater trochanter and the shoulder to represent both the trunk and pelvis angle. This method has been used previously (McLaughlin, et al., 1977, 1978; Lander et al., 1986; Russell & Phillips, 1989; Fry et al., 1993), but it makes the assumption that the spine is a fixed rod, which it most definitely is not. RQ2. How do the forces and moments, calculated using a two dimensional model, at the ankle, knee, and hip joints, as well as the forces and moments experienced in the lumbar region, differ among the three squat lifts at the lowest point of descent? L Since the lower extremity was in an unloaded state during the seated box squat (Boxl), it is not surprising that the forces at the ankle and moments of the ankle, knee, and hip were significantly lower than the parallel, partial, or portion of the box squat off of the box (Box2) (Figures 39-41). Discussion will be limited to comparisons of parallel, partial, and Box2 positions, except for the lower back moments where all four conditions will be compared. Moments were reported in Nm/kg to control for the effects of body weight on the results (Moisio et al., 2003; Winter, 1991). A unique finding of this study was significantly greater anterior/posterior forces but significantly lower vertical forces at the joints during the Box2 stage compared to the lowest point of descent in the parallel and partial squat. This would mean that there would be greater shear forces and lower compressive forces at the ankle joint as the participants were leaving the box compared to the parallel or partial squat. It is not prudent to state that the shear forces were greater at the knee, hip, and lower back since shear and compressive forces were not directly measured and would vary depending on 187 the knee and lower back angle. Whether these differences affect the joints over time could not be ascertained from this study, but should be evaluated in future research. Likewise further analysis evaluating compressive and shear forces instead of horizontal and vertical forces may be more prudent for future evaluation. Ankle joint moments have not typically been reported in previous research. Most likely this is because there has been little differences in ankle moment values which would be the case in this study if only typical squat movements such as the parallel and partial squat were evaluated. The ankle moment is primarily dependent on the vertical ground reaction force and the distance of this force from the center of mass of the foot. It appears that the center of pressure/center of mass relationship is very similar in parallel and partial squat. However, the Box2 condition had a significantly lower ankle moment compared to the parallel and partial squat. This would indicate that the participants had their center of pressure closer to their heels during the Box2 condition compared to parallel and partial, where the center of pressure was closer to the mid-foot. Greater ankle moments would suggest that there is more demand on the plantar flexors for support and extension at the ankle during the parallel and partial squat compared to the box squat. Thus, there is less initial demand on the plantar flexors of the foot in the initial portion of the box squat. This finding may justify using the “toe raise” (plantar flexion) at the end of the box squat. By performing the plantar flexion, the plantar flexors (e.g., the gastrocnemius) would then have more stress placed upon it to cause adaptation. This finding may also be part of the reason for the idea that recovery is faster. Since there is less demand placed upon the plantar flexors, that portion of the leg may not fatigue as quickly as it would performing parallel or partial squats. 188 Knee and hip moments had expected results. The knee and hip moment values are comparable to previous research. Escamilla, Lander, and Garhammer (2000) reported that normal absolute mean knee moments range between 100 and 300 Nm for the parallel squat. The mean absolute knee moment for the parallel squat in this study was 137 Nm. The values are on the low end of the spectrum most likely because a 10RM was used for the weight and the ability levels of the participants in this study are likely to be lower I: than previous studies. Escamilla et al. (1998) reported peak knee moments of 175 Nm with experienced male weightlifters using a 12RM weight. Hip moment values also are comparable to previous research. Wretenburg et al. (1993) reported mean absolute hip I moments of approximately 200 Nm for the parallel squat and this study found mean absolute hip moments during the parallel squat to be approximately 250 Nm. Wretenburg et al.’s (1993) participants used 65% of their lRM while participants in the current study used a 10RM which often equates to 75-85% of a person’s lRM (Bachle & Earle, 2000). The one unexpected result was the similar knee moment values for the partial and Box2 conditions. These similar values may be partially explained by the increased anterior posterior forces experienced during the Box2 condition. The greater knee and hip moments show that there was more force demand for the knee extensors (rectus femoris and vastus lateralis) and hip extensors (gluteus maximus and biceps femoris) during the parallel squat. The lower hip moment experienced during the box squat would not support the notion the box squats develop hips to a greater extent. However, box squats are performed with greater weights and the increased weight may make the hip moments comparable to the parallel squat hip moments. 189 The higher horizontal force at the lower back during the Boxl condition does raise a concern. Since the lower back (i.e., trunk) is in a nearly perpendicular position to the horizontal, this would suggest that there are greater shear forces being produced at the lower back. These greater shear forces would mean there is a higher chance for injury such as a slipped disc. However, as discussed in the joint angles section of this chapter, the model of the trunk in this study is very simplistic and does not account for many of the factors that lead to actual injury of the lower back such as pelvis and spine alignment and the curvature of the spine. Modeling the trunk as a rigid rod precludes any definitive statements about the effects of this higher horizontal force. More research should be performed on the box squat evaluating the possible effects of this higher horizontal force with a more in-depth model. Lower back moment values are also comparable to previous research. Russell and Phillips (1989) reported lower back moments between 170 and 800 Nm in eight experienced weightlifters performing a back squat (parallel squat). This current study found lower back moments to range between 180 and 545 Nm for the parallel squat. The results are also as expected. With greater forward trunk lean, there is a greater lower back moment. The smaller lower back moment during the seated box position (Boxl) must be interpreted cautiously. While it would be easy to state that a lower moment would mean that there is less potential for injury to the back, this evaluation also suffers from the same problems as the calculation of the lower back angle and the evaluation of the horizontal forces during the Boxl condition. The lower back moment is a measure of moments affecting the trunk with the assumption that it is a rigid rod. Nachemson and Morris (1964) and Andersson et al. (1974a, b, c, (1) reported increased intradisc pressure 190 due to changes in the normal curvature of the spine. This study could not assess the changes in curvature that would occur with the change in pelvic tilt in relationship to the vertebrae due to the problems discussed previously. Using the greater trochanter and shoulder markers does not allow for any evaluation of the pelvic alignment with respect to the upper trunk. Furthermore, this study can only report forces and cannot account for the intra-abdominal muscle forces and pressures that also contribute to the stresses placed on the spine. RQ3. How does recruitment of the vastus lateralis, rectusfemoris, biceps femoris, gluteus maximus, gastrocnemius, and erector spinae muscles difler among the three squatting lifts (parallel, box, and partial) ? The EMG activity, when evaluated as a percentage of total muscle activity, showed similar but mixed results compared to Caterisano et al’s 2002 study. Caterisano et al. (2002) compared EMG activity, as a percentage of total muscle activity, of the vastus lateralis, vastus medialis, biceps femoris, and gluteus maximus in three conditions (partial, parallel, and full squat). This current study evaluated the rectus femoris, vastus lateralis, gastrocnemius, bicep femoris, gluteus maximus, and erector spinae. The distinct comparison of percentage contribution of each muscle between the two studies (Caeterisano et al. and the current study) would not be prudent because different muscles were used to find total muscle activity and, thus, would not necessarily provide the same relative contribution. Additionally, the definition of each squat in the Caterisano et al. (2002) study is different than how the squats were defined in this current study. In the Caterisano study, a partial squat was a squat to a depth where the knee angle was 135 degrees. The parallel squat was to a depth where the knee angle was 90 degrees. This 191 would have corresponded to the partial squat in the current study. The full squat in the Caterisano study was to a depth where the knee angle was approximately 45 degrees. This depth was much greater than parallel squat depth (knee angle approximately 70 degrees) observed in this eturent study. Both studies found that the vastus lateralis provided the highest contribution to the lift when the knee angle was approximately 90 degrees and that the relative contribution slightly decreased as depth increased. Likewise, both studies found that the contribution of the bicep femoris did not change significantly when comparing the 90 degree knee angle and the condition where the knee angle was less than 90 degrees. However, Caterisano et al. (2002) reported increasing contribution of the gluteus maximus, during the contentric phase of the lift, when the depth of squat increased. The current study did not show the same findings. A possible reason for this discepancy is that the current study included the erector spinae, which showed a distinct increase in contribution as depth increased. Since each muscle’s relative contribution depends upon the other muscles, the inclusion of the erector spinae may have masked the relative changes in gluteal activity observed in Caterisano et al.’s (2002) study. The relative contribution of each muscle when compared between the three lifts (parallel, box, and squat) showed few significant differences (Figures 43-46). The percentage contribution of the rectus femoris was significantly greater during the box squat compared to the parallel and partial squats. The rectus femoris muscle crosses the hip joint and has a role in hip flexion as well as knee extension. In the seated position of the box squat, the partipants would need to rotate their hips forward as they returned to 192 their feet support only positon, thus the rectus femoris would not be completely relaxed like the vastus lateralis (Figure 42). The relative contribution of the bicep femoris muscle during the box squat was significantly less (p<.05) than during the parallel and partial squat. This difference is most likely due to the fact the the box could be used to decelerate the descending body and that the movement pattern to stand up off of the box did not require as much use of the biceps femoris as a normal squat (parallel or partial). The gluteal activity, as measured as a percent of total muscle activity, during the performance of the box squat was only significantly less than the partial squat when the outliers were removed and was less, though not significantly less, than the parallel squat. These results would not support the idea of box squats developing the hip extensors to a greater extent. Overall, the evaluation of muscle activity as a percent of total activity did little to distinquish any lift from the others. The EMG data, when normalized to a reference test, had similar results for the rectus femoris, vastus lateralis, and biceps femoris as Wretenburg et al. (1993). It should be noted that Wretenburg et al. (1993) only measured these three muscles and that the eccentric and concentric portions were not examined seperately. F urtherrnore, Wrenteburg et al. (1993) evaluated the EMG signal using a full wave rectified, low pass filtered time averaged algorithm (i.e., linear envelope) where the current study used a high pass filter prior to averaging the signal. Wrenteburg et al. (1993) reported average normalized values of approximatley .8 and 1.5, 1.0 and 1.7, and 1.0 and 2.0 for the rectus femoris, vastus lateralis, and biceps femoris in the 90 degree (partial) and parallel positions, respectively. When the eccentric and concentric values are averaged for the 193 current study, the averages were 1.0 and 1.3, 1.4 and 1.5, and 1.7 and 2.2 for the rectus femoris, vastus lateralis, and biceps femoris in the 90 degree (partial) and parallel positions, respectively. The box squat EMG data, when normalized to the reference test, was significantly lower than the parallel and partial squats for most muscles (Figures 47-50). When looking at temporal examples of the EMG signals (Figure 42), the reason for these lower values is relatively clear. The majority of muscles have minimal activity during the seated portion of the box squat which would drastically reduce the average activity over these portions of the lift. The fact that the gluteus maximus had lower average normalized EMG activity would not support the idea that box squats develop the hip extensors to a greater extent. Furthmore, this lower average muscle activity could possibly lead to less adaptation over longer periods of training. RQ4. Is there a relationship among the electrical activity of selected muscles and the forces and moments experienced at the lowest point of descent? As stated in the results section, this research question was not answered due to the analysis methods used with the EMG data. The forces and moments were evaluated at a single time point, but the EMG signal was averaged over the course of the eccentric and concentric portions of the lift. To appropriately address this research question, the EMG data would have needed to have been analyzed using rectified integration and a fixed time reset to zero (Winter, 1990). However, the EMG data had already been evaluated using two different methods and a third evaluation of the same data would not be prudent. 194 RQ5. How do selected performance parameters (maximum vertical jump and anaerobic endurance as measured by a Bosco jump test) of participants change due to completing workouts of the three different squatting exercises? Maximum vertical jump. There was minimal decrease in vertical jump height post-workout regardless of workout condition (Figure 51). The 15 minute recovery time was necessary due to the location of the Vertec with respect to motion analysis equipment. While it would have been interesting to have testing immediately after completion of the workout, these results still do provide important information. These results would suggest that using parallel squat weight during a partial or box squat workout does not produce fatigue or that recovery has already occurred by 15 minutes. However, it would be very unlikely for an athlete to participate in a competition 15 minutes after completion of a weight training workout. Bosco jump test. Anaerobic endurance as measured by the Bosco jump test showed no differences across all three workout conditions when compared to the reference test (Figure 52). This would suggest that the participants had fully recovered from the workout sessions three hours post-workout regardless of what type of workout session occurred. The three hour recovery time was chosen for two reasons. First, Woolstenhulme et al.’s (2004) reported that female basketball players had non-significant differences in anaerobic power, as measured by a Wingate cycle test, six hours after completion of a moderate workout using four sets of 8-12RM for seven exercises. It seemed prudent that the time frame should be much shorter. Second, Raastad and Hallen (2000) reported that leg extensor strength had returned to pre-workout levels three hours after a moderate leg workout out (70% of 3RM for back and front squats, and 70% of 6RM for leg extension). The workout in this study would also be considered a moderate 195 intensity workout and it was expected that the participants would be close to recovery by three hours, but it was expected for the participants to still be somewhat fatigued. A shorter rest period after the performance of the workout most likely would have revealed different results. However, this study does add support previous research that has shown that recovery to pre-workout measures after a moderate bout of strength training occurs in approximately three hours. The Bosco jump test has been shown to be a reliable measure of anaerobic endurance in an unfatigued state. Bosco et al. (1983) reported that test-retest measures for the Bosco to be very high (r =.95, p<.01) when evaluated on an Italian male volleyball student team (n=12, mean age = 21.7). Likewise, Sands (2000) reported test- retest reliability (one month between testing dates) using intraclass correlation coefficients = .87 on athletes preparing for the Olympic games. However, no known studies have used the Bosco jump test to evaluate changes in fatigue. Bosco, et al. (1983) reported that school aged boys (n=14, mean age=l7.8) had an average Watts/kg score of 22.2 (SD =1.8). This is much higher than the values observed during this testing (reference test mean = 14.12, SD=3.17 Watts/kg). However, Sands et al. (2004) reported values of 17.81 (SD=2.73) Watts/kg for male and 12.19 (SD=2.39) Watts/kg for female collegiate track athletes. The results of Sands et al. (2004) suggest that the population that was evaluated during the current study would not be elite athletes. It could be speculated that most of the other studies reported involved more elite athletes and more studies need to be performed on the “typical” high school athlete to determine test-retest reliability. 196 RQ6. How do participants ’ perceived effort, immediately after bouts of the three different squat exercises, differ? Several studies have evaluated how RPE changes with different intensities of weight training (Day et a1. 2004; Gearhart et al., 2001; Sweet et al., 2004), but this is the first known study to evaluate how RPE changes with changes in how the exercise is performed. As expected, the perceived effort of performing the parallel squat workout was significantly greater than both the partial and box squat workouts. Even though the exact same weight was used for all three workouts, the parallel squat workout would have had more work performed due to the lower depth of the squat. Additionally, greater moments were produced at the knee, hip, and lower back when compared to the box squat, and the knee and hip when compared to the partial squat. These greater moments due to reaching such a depth would most likely also play a role in the participants’ ratings of effort. RQ 7. Is there a relationship between participants ’ perceived eflort and the rate of recovery? Even though the three workouts were perceived to require different effort levels, this was not reflected in the recovery data. Only the parallel squat workout was associated with a reduction in vertical jump height. Furthermore, there were no differences in Bosco jump test data 3 hours post-workout. These findings show that RPE may not be a good indicator of how much recovery is needed after bouts of weight training. No known studies have previously evaluated RPE and rate of recovery. However, athletes report higher RPE values with higher intensity weight training (heavier weights) (Day et al., 2004; Sweet et al., 2004) and higher intensity weight training has 197 L'. l.‘ . _'__' .-- been shown to cause longer periods of recovery (Raastad & Hallen, 2000). As was stated in the discussion of research question five, the recovery time was too long in this study to identify differences in recovery and a shorter recovery time would have most likely led to different results. Implications for Coaches and Athletes The purpose of this study was to determine if there was any benefit in (a) recovery of the lower extremity and (b) hip development due to the performance of box squats compared to parallel or partial squats. This study found that there was no benefit to recovery when box squats are performed at the same weight, number of repetitions, and allowed recovery time as parallel or partial squats. The only difference was shown primarily at 15 minutes after the workout in the vertical jump. There would be very few, if any, situations where a power activity would be performed so soon after a weight training episode. Furthermore, partial squats had equivocal recovery compared to box squats. Thus, the performance of partial squats may be an alternative choice in lifting if a change in lift is desired from one workout to another. The belief that box squats develop the hips to a greater extent was also not supported. The box squat did not produce greater average gluteal muscle activity when normalized to a reference test compared to the parallel or partial squat, or when evaluated as a percent of total muscle activity compared to the parallel squat. Furthermore, performance of the box squat resulted in lower average normalized muscle activity for the majority of muscles evaluated in this study. This could possibly lead to less training adaption over time. However, in practice, the box squat uses much higher weights than the parallel squat and this may result in greater recruitment of the muscles evaluated in 198 this study (rectus femoris, vastus lateralis, gastrocnemius, biceps femoris, gluteus maximus, and erector spinae). Further research should be performed to evaluate the changes due to performing box squats at a higher intensity. While there were no definitive negative results from performing box squats in this study, the additional equipment needed to perform the box squat (i.e., the box) may be an unnecessary expense for schools or teams to purchase if there is no benefit to its performance compared to the partial or parallel squat. Future Research ‘ 1. This study should be repeated using relative weights compared to absolute loads. H Considerably more weight is lifted during the performance of box squats in practice compared to parallel squats. Performing a similar study where, for example, 70% of the lRM for box squats was compared to 70% of lRM for parallel squats would fully answer the question if there is a benefit to recovery by performing box squats. However, the current study already has shown that, if the intensities are kept in what is considered to be moderate intensity, there would be minimal differences and the little advantage box squats provided should be negated. This study should be performed with elite athletes who might exhibit a more consistent response to training and a more consistent output on anaerobic tests such as the Bosco jump test. Implementation of this testing protocol with a collegiate team might show different results on the amount of anaerobic endurance recovery after the training bouts. 199 3. This study demonstrated that there was some fatigue produced from the performance of parallel squats as measured by maximal vertical jump performance. The testing methods did not allow for determination if this was central fatigue or peripheral fatigue. It may be more prudent to use a maximal isometric leg extension test during which EMG is recorded so that assessments as to whether the stimulus or the actual muscles ability to contract is reduced. 4. This study was not able to address whether box squats were potentially harmfirl to the lower back. Lower back moments were calculated during the seated portion of the box squat. However, this was a very crude model of the spine and did not account for changes in curvature of the spine or rotation of the pelvis. These changes have been shown to increase intradisc pressure and would provide a more realistic evaluation of the potential danger of this lift. This was not evaluated due to room limitations which then limited marker placement and evaluation. A true 3-D evaluation would need to be performed that allowed for proper marking of the pelvis without loss of marker view due to limb or weight obstruction. More markers would also be needed to provide a realistic change in the curvature of the spine. 5. This study only evaluated a moderate training stimulus. Multiple training stimuli are used in practice. It would be beneficial to repeat this study at other intensities to determine if the rate of recovery would remain the same across all stimuli. 6. This study did not measure multiple day recovery and delayed onset of muscle soreness (DOMS) from the workout. Delayed onset of muscle soreness most likely would not occur after a moderate workout in individuals that have been 200 weight training regularly. However, DOMS may be greater after weight training performing parallel squats compared to performing box squats. If there was greater DOMS after parallel squats, it would be perceived that recovery was faster alter performance of box squats. Limitations The evaluation of joint angles, forces and moments in this study could only be performed in two dimensions due to the constraints of the lab. While this would not drastically change the evaluation of the lower limb joints (ankle, knee, hip), it did limit the evaluation at the lower back. It was difficult to recruit subjects for this study due to the multiple testing times. Even though participants were recruited out of their normal sporting season, they often had off-season training (and often for multiple sports) and/or physical education classes that could not be avoided. The restriction of 48 hours between weight training of the lower extremity was strictly enforced, but limiting other activities was extremely difficult. The majority of participants had less than 30 minutes of sports training the day prior to a testing session. It was difficult to complete the sessions in a timely manner due to participant commitments. The greatest length of time between sessions was three weeks. This occurred with three subjects and was between the second and third testing sessions. The greatest amount of time between the three workout sessions was 15 days- Idealistically, it would have been beneficial to have the sessions closer together. 201 4. The finishing movement of the box squat was not strictly controlled. Participants were allowed to perform the movement as they normally did in practice. Many of the subjects finished by performing plantar flexion. This part of the testing should have been more strictly regulated. However, it was not the main focus of the testing and would not affect any results except the EMG values for the gastrocnemius. This study used a repeated measures design that tried to limit instrumentation error by checking the marker placement on each testing session and using Henne dye to maintain electrode placement. However, EMG measurements would still inherently have error due to variables beyond the researchers’ control (e. g., changes in hydration levels from one session to the next). It would be more ideal to have a single session for motion analysis and EMG data collection. Subjects’ 10RM was determined with the criteria that the 10 repetitions must be performed with proper form. Most subjects may have been able to perform with more weight or perform more repetitions, but the form was the limiting factor for many. This may have allowed some subjects to have less overall fatigue when finished. However, safety was a priority and going to true exhaustion would be very difficult in the general testing of these subjects. 202 APPENDIX A IRB Applications and Consent/Assent Forms 203 Parental Permission Form “Biomechanical and physiological comparison of three methods of back squatting. ” Primary Investigator: Eugene Brown PhD, Department of Kinesiology, Michigan State University Secondary Investigator: Adam Bruenger MS, Department of Kinesiology Michigan State University This study is being conducted as a doctoral dissertation: This study has two purposes. First, this study will compare the biomechanical parameters (joint angles and forces) and muscle activity that occur during the performance of three different back squatting techniques (box, partial, and parallel squat) commonly used by high school athletes. Second, this study will compare a person’s ability to recover after sessions of these different squatting techniques. Your child’s maximal vertical jump height and performance of multiple jumps over one minute will be used to determine the amount of recovery. The primary goal of this study is to evaluate if there is any benefit of performing one of these methods of squatting over the other two. It is believed that a shorter recovery time is needed after performing a workout with box squats compared to performing a workout with parallel squats. However, no scientific studies have been performed to evaluate the validity of this statement. This study will provide some insight into possible reasons for the differences between the lifts. Your child’s school was identified as one that uses these particular methods of squatting as part of their strength training protocol. Evaluation of these different squatting methods will allow coaches, including the ones at your child’s school, to make a more informed choice whether or not to use such techniques. Your child’s total time commitment for this study would be approximately 15 hours. After the general information session, participants would be asked to participate in five testing sessions scheduled on separate dates. The anthropometric data collection and squat maximum testing session is estimated to last approximately 1 hour. The repeated jump test is estimated to last .5 hours. The three workout sessions will require approximately 4.5 hours each. In addition, it is imperative that participants be free of any orthopedic condition of the lower extremities that may hinder their ability to perform these three squat techniques. The data collection process will have the following stages: 1) General Information - After explanation and description of the study and subject consent, a questionnaire will be distributed among the participants to collect information to determine if there are any previous or current injuries/illnesses that should exclude the potential participant from the study. This assessment instrument will be administered prior the collection of any anthropometric data. 204 2) 3) 4) Anthropometric Measurements and Squat Maximum Testing— All anthropometric data will be collected in private (parents or guardians may accompany their child) in the Department of Kinesiology’s Biomechanics Research Station located in the IM Sports Circle Building on the campus of Michigan State University or at your child’s high school’s weight room. 0 Weight will be assessed on a standard weight balance while your child is wearing shorts and t-shirt. Height will be assessed with a standard anthropometer. Sitting height will be assessed with a standard anthropometer while your child is seated on a bench. o Segmental lengths will be determined with the use of standard body calipers. Specifically foot, shank, thigh, pelvis, trunk, and head lengths and widths will be assessed. 0 Skinfolds will be used to estimate percent body fat. Specifically, Skinfolds of the triceps, subscapularis (shoulder blade), and chest will be taken. A squat maximum will be assessed after completion of the anthropometric data collection and will also occur at the Biomechanics Research Station or at your child’s high school’s weight room. A ten repetition maximum for the parallel squat will be performed. Proper warm up will be performed prior to this test. Experienced spotters will monitor every lift to help prevent injury. Repeated Jump Test- The repeated jump test consists of your child performing maximal vertical jumps with his hands on his hips for 1 minute while having one foot on a force platform. This session is separate from the other sessions because he needs to be in an unfatigued state to provide a reference of maximal ability. This testing session will occur at the Biomechanics Research Station in 1M Circle. Workout/Recovery Sessions — These sessions will be used to determine your child’s rate of recovery from performing the different squatting exercises. These sessions will occur at the Biomechanics Research Station in [M Circle, the Biomechanics Gait Lab in West Fee, or a combination of both facilities. The following protocol will be used: 0 Your child will be asked to perform the exercise in minimal clothing to allow for accurate assessment of body landmarks. Boys will be asked to perform these squat techniques wearing tight fitting (e. g., biker) shorts and either no shirt or an “Under Armor” top. 0 Prior to actual data collection, your child will have approximately 15 reflective joint markers affixed to points on the segments of the lower limbs. 205 In addition, your child will have a very small portion of his calf, thigh, hamstring, buttocks, and lower back lightly abraded and cleansed in order to affix several surface electromyography (SEMG) electrodes necessary to assess muscle activity of the aforementioned muscles. In order to collect an electromyographic signal that is of high quality, it is important to gently abrade the exposed skin and cleanse with rubbing alcohol to remove any debris that may impede signal quality. Skin preparation and electrode placement will be performed by an investigator of the same sex as the participant. To ensure that the markers and electrodes are placed in the same spot during each workout session, your child will be marked with Henne tattoo dye where the markers/electrodes come in contact with the skin. This dye lasts for approximately 2-3 weeks, but will disappear. Your child will be asked to follow a warm up that should be similar to his normal warm up prior to strength training. Your child will be asked to perform a maximum vertical jump. He will jump as high as possible and his jump height will be recorded using a Vertec measuring device. Your child will then perform a workout of either box squats, partial squats, or parallel squats. Experienced spotters will monitor every lift to help prevent injury. Video cameras will be used to determine quantitative and qualitative data with respect to comparing the three different squat techniques. In addition to the video recording of each squat trail, forces applied to the ground will be simultaneously collected via force platform to assist in the determination of forces that are incurred at the knee and hip joint and also in the lower back. Your child then will perform the maximal vertical jump again. Your child will be asked to rest for 3 hours. During this time, a room in IM Sports Circle will be provided for him to eat, watch movies, read, complete homework, etc. At the end of 3 hours, your child will again perform the maximal vertical jump test, and also perform the repeated jump test. A snack may be provided, but we ask that your child bring his own lunch if he is tested over a meal time. If your child attends a session at IM Circle during the week while parking is enforced, his parking fee will be reimbursed. Please turn in his receipt for parking to Adam Bruenger who will pay him by check. 206 Your child is being asked to participate in this study because he is a competitive athlete that has experience with the squatting techniques of interest. After completion of the third workout testing session (the final testing session), your child will be given a check for $25 to help defray the cost of gasoline and a T-shirt as thanks for his participation in this study. Your child’s participation is totally voluntary, and he may chose to participate or not, as well as to discontinue his participation at any time without any explanation. By giving your permission to allow your child to participate in this study, you agree that the materials and data generated (video, pictures, and measurements) of your child may be used for research and academic purposes. If your child does so choose to discontinue participation, all data, including video footage, will be destroyed. You have also been assured that your child’s privacy will be protected to the maximum extent allowable by law. When this research is completed, an abstract of the results will be mailed to him. He may also seek personal data for comparison of the three different squatting techniques. This study consists of activities that your child uses in his regular strength training protocols at his school. Thus, the risk for injury during this study is no different than what would be expected during his regular training. Less than maximal weights will be used during the kinematic/kinetic session to lower the chances of a failed attempt and experienced spotters will monitor every lift to help prevent injury. However, there is always a possibility of injury. Possible injuries include muscle strains and injury to the lower back due to the nature of the lifting techniques being used. Though not life threatening, the abraded skin may be discolored for a few days after the testing or even scab. In the unlikely event that your child is injured as a result of participation in this research project, Michigan State University will assist you in obtaining emergency medical care, if necessary, for your child’s research related injuries. If you have insurance for medical care, your medical provider will be billed in the ordinary manner. As with any medical insurance, any costs that are not covered or are in excess of what are paid by your insurance, including deductibles, will be your responsibility. The University’s policy is to not provide financial compensation for lost wages, disability, pain or discomfort, unless required by law to do so. This does not mean you are giving up any legal rights you may have. You may contact Dr. Eugene Brown ino. (517) 353-6491, email: ewbrown@msu.edu, with any questions or to report an injury. If you have any questions about this study, please contact Dr. Eugene Brown inc. (517) 353-6491, email: ewbrown@msu.edu, or Adam Bruenger inc. (517) 432- 4073, email: bruenger@msu.edu at the Department of Kinesiology, Michigan State University. If you have questions or concerns regarding your child,s rights as a study participant, or are dissatisfied at any time with any aspect of this study, you may contact — anonymously, if you wish- Peter Vasilenko, Ph.D., Director of Human Research Protections, (517)355-2180, fax (517)432-4503, e-mail irb@msu.edu, mail 202 Olds Hall, Michigan State University, East Lansing, MI 48824-1047. 207 Parental Permission Form “Biomechanical and physiological comparison of three methods of back squatting. ” Primary Investigator: Eugene Brown PhD, Department of Kinesiology, Michigan State University Secondary Investigator: Adam Bruenger MS, Department of Kinesiology Michigan State University This study is being conducted as a doctoral dissertation: Your signature below indicates your voluntary agreement for your child to participate in this research study Name of participant: Date of birth: (Print) Name of parent (guardian): (Print) Signature of parent: Date: Mailing address: Phone: e-mail address: 208 Minor Assent Form “Biomechanical and physiological comparison of three methods of back squatting. ” Primary Investigator: Eugene Brown PhD, Department of Kinesiology, Michigan State University Secondary Investigator: Adam Bruenger MS, Department of Kinesiology Michigan State University This study is being conducted as a doctoral dissertation: This study has two purposes. First, this study will compare the biomechanical é. parameters (joint angles and forces) and muscle activity that occur during the L; performance of three different back squatting techniques (box, partial, and parallel squat) commonly used by high school athletes. Second, this study will compare a person’s ability to recover after sessions of these different squatting techniques. Your maximal vertical jump height and performance of multiple jumps over one minute will be used to determine the amount of recovery. The primary goal of this study is to evaluate if there is any benefit of performing one of these methods of squatting over the other two. It is believed that a shorter recovery time is needed after performing a workout with box squats compared to performing a workout with parallel squats. However, no scientific studies have been performed to evaluate the validity of this statement. This study will provide some insight into possible reasons for the differences between the lifts. Your school was identified as one that uses these particular methods of squatting as part of their strength training protocol. Evaluation of theses different squatting methods will allow coaches, including the ones at your school, to make a more informed choice whether or not to use such techniques. Your total time commitment for this study would be approximately 15 hours. After the general information session, participants would be asked to participate in five testing sessions scheduled on separate dates. The anthropometric data collection and squat maximum testing session is estimated to last approximately 1 hour. The repeated jump test is estimated to last .5 hours. The three workout sessions will require approximately 4.5 hours each. In addition, it is imperative that participants be free of any orthopedic condition of the lower extremities that may hinder their ability to perform these three squat techniques. The data collection process will have the following stages: 1) General Information — After explanation and description of the study and subject consent, a questionnaire will be distributed among the participants to collect information to determine if there are any previous or current injuries/illnesses that should exclude the potential participant from the study. This assessment instrument will be administered prior the collection of any anthropometric data. 209 2) Anthropometric Measurements and Squat Maximum Testing— All 3) 4) anthropometric data will be collected in private (parents or guardians may accompany their child) in the Department of Kinesiology’s Biomechanics Research Station located in the IM Sports Circle Building on the campus of Michigan State University or at your high school’s weight room. 0 Weight will be assessed on a standard weight balance while you are wearing shorts and t-shirt. Height will be assessed with a standard anthropometer. Sitting height will be assessed with a standard anthropometer while you are seated on a bench. 0 Segmental lengths will be determined with the use of standard body calipers. Specifically foot, shank, thigh, pelvis, trunk, and head lengths and widths will be assessed. 0 Skinfolds will be used to estimate percent body fat. Specifically, Skinfolds of the triceps, subscapularis (shoulder blade), and chest will be taken. A squat maximum will be assessed after completion of the anthropometric data collection and will also occur at the Biomechanics Research Station or at your high school’s weight room. A ten repetition maximum for the parallel squat will be performed. Proper warm up will be performed prior to this test. Experienced spotters will monitor every lift to help prevent injury. Repeated Jump Test- The repeated jump test consists of you performing maximal vertical jumps with your hands on your hips for 1 minute while having one foot on a force platform. This session is separate from the other sessions because you need to be in an unfatigued state to provide a reference of maximal ability. This testing will occur at the Biomechanics Research Station. Workout/Recovery Sessions — These sessions will be used to determine your rate of recovery from performing the different squatting exercises. These sessions will occur at the Biomechanics Research Station in IM Circle, the Biomechanics Gait Lab in West Fee, or a combination of both facilities. The following protocol will be used: 0 You will be asked to perform the exercise in minimal clothing to allow for accurate assessment of body landmarks. Boys will be asked to perform these squat techniques wearing tight fitting (e.g., biker) shorts and either no shirt or an “Under Armor” top. 0 Prior to actual data collection, you will have approximately 15 reflective joint markers affixed to points on the segments of the lower limbs. 210 In addition, you will have a very small portion of your calf, thigh, hamstring, buttocks, and lower back lightly abraded and cleansed in order to affix several surface electromyography (SEMG) electrodes necessary to assess muscle activity of the aforementioned muscles. In order to collect an electromyographic signal that is of high quality, it is important to gently abrade the exposed skin and cleanse with rubbing alcohol to remove any debris that may impede signal quality. Skin preparation and electrode placement will be performed by an investigator of the same sex as the participant. To ensure that the markers and electrodes are placed in the same spot during each workout session, you will be marked with Henne tattoo dye where the markers/electrodes come in contact with the skin. This dye lasts for approximately 2-3 weeks, but will disappear. You will be asked to follow a warm up that should be similar to your normal warm up prior to strength training. You will be asked to perform a maximum vertical jump. You will jump as high as possible and your jump height will be recorded using a You will then perform a workout of either box squats, partial squats, or parallel squats. Experienced spotters will monitor every lift to help prevent injury. Video cameras will be used to determine quantitative and qualitative data with respect to comparing the three different squat techniques. In addition to the video recording of each squat trail, forces applied to the ground will be simultaneously collected via force platform to assist in the determination of forces that are incurred at the knee and hip joint and also in the lower back. You then will perform the maximal vertical jump again. You will be asked to rest for 3 hours. During this time, a room in IM Sports Circle will be provided for you to eat, watch movies, read, complete homework, etc. At the end of 3 hours, you will again perform the maximal vertical jump test, and also perform the repeated jump test. A snack may be provided, but we ask that you bring your own lunch if you are tested over a meal time. If you attend a session at M Circle during the week while parking is enforced, your parking fee will be reimbursed. Please turn in your receipt for your parking to Adam Bruenger who will pay you by check. 211 You are being asked to participate in this study because you are a competitive athlete that has experience with the squatting techniques of interest. After completion of the third workout testing session (the final testing session), you will be given a check for $25 to help defray the cost of gasoline and a T-shirt as thanks for participation in this study. Your participation is totally voluntary, and you may chose to participate or not, as well as to discontinue your participation at any time without any explanation. By participating in this study you agree that the materials and data generated (video, pictures, and measurements) may be used for research and academic purposes. If you do so choose to discontinue participation, all data, including video footage, will be destroyed. You have also been assured that your privacy will be protected to the maximum extent allowable by law. When this research is completed, an abstract of the results will be Fm mailed to you. You may also seek personal data for comparison of the three different i squatting techniques. This study consists of activities that you use in your regular strength training protocols at your school. Thus, the risk for injury during this study is no different than what would be expected during your regular training. Less than maximal weights will be used during the kinematic/kinetic session to lower the chances of a failed attempt and ' experienced spotters will monitor every lift to help prevent injury. However, there is always a possibility of injury. Possible injuries include muscle strains and injury to the lower back due to the nature of the lifting techniques being used. Though not life threatening, the abraded skin may be discolored for a few days after the testing or even scab. In the unlikely event that you are injured as a result of your participation in this research project, Michigan State University will assist you in obtaining emergency medical care, if necessary, for your research related injuries. If you have insurance for medical care, your medical provider will be billed in the ordinary manner. As with any medical insurance, any costs that are not covered or are in excess of what are paid by your insurance, including deductibles, will be your responsibility. The University’s policy is to not provide financial compensation for lost wages, disability, pain or discomfort, unless required by law to do so. This does not mean you are giving up any legal rights you may have. You may contact Dr. Eugene Brown ino. (517) 353-6491, email: ewbrown@msu.edu, with any questions or to report an injury. If you have any questions about this study, please contact Dr. Eugene Brown ino. (517) 353-6491, email: ewbrown@msu.edu, or Adam Bruenger inc. (517) 432- 4073, email: bruenger@msu.edu at the Department of Kinesiology, Michigan State University. If you have questions or concerns regarding your rights as a study participant, or are dissatisfied at any time with any aspect of this study, you may contact — anonymously, if you wish- Peter Vasilenko, Ph.D., Director of Human Research Protections, (517)355-2180, fax (517)432-4503, e-mail irb@msu.edu, or by regular mail 202 Olds Hall, Michigan State University, East Lansing, MI 48824-1047. 212 Minor Assent Form “Biomechanical and physiological comparison of three methods of back squatting. ” Primary Investigator: Eugene Brown PhD, Department of Kinesiology, Michigan State University Secondary Investigator: Adam Bruenger MS, Department of Kinesiology Michigan State University This study is being conducted as a doctoral dissertation: Name of participant(Print): Sign your name below only if you are sure you understand the purpose of this study and are willing to participate in this study. Signature Date 213 Consent Form (Consent version for college students over 18 years of age) “Biomechanical and physiological comparison of three methods of back squatting. ” Primary Investigator: Eugene Brown PhD, Department of Kinesiology, Michigan State University Secondary Investigator: Adam Bruenger MS, Department of Kinesiology Michigan State University This study is being conducted as a doctoral dissertation: This study has two purposes. First, this study will compare the biomechanical parameters (joint angles and forces) and muscle activity that occur during the performance of three different back squatting techniques (box, partial, and parallel squat) commonly used by high school athletes. Second, this study will compare a person’s ability to recover after sessions of these different squatting techniques. Your maximal vertical jump height and performance of multiple jumps over one minute will be used to determine the amount of recovery. The primary goal of this study is to evaluate if there is any benefit of performing one of these methods of squatting over the other two. It is believed that a shorter recovery time is needed after performing a workout with box squats compared to performing a workout with parallel squats. However, no scientific studies have been performed to evaluate the validity of this statement. This study will provide some insight into possible reasons for the differences between the lifts. You are being recruited for this study because you have experience with the weightlifting techniques being evaluated. Evaluation of these different squatting methods will, in general, allow coaches to make a more informed choice whether or not to use such techniques. Your total time commitment for this study would be approximately 15 hours. After the general information session, participants would be asked to participate in five testing sessions scheduled on separate dates. The anthropometric data collection and squat maximum testing session is estimated to last approximately 1 hour. The repeated jump test is estimated to last .5 hours. The three workout sessions will require approximately 4.5 hours each. In addition, it is imperative that participants be free of any orthopedic condition of the lower extremities that may hinder their ability to perform these three squat techniques. The data collection process will have the following stages: 214 1) 2) 3) 4) General Information - After explanation and description of the study and subject consent, a questionnaire will be distributed among the participants to collect information to determine if there are any previous or current injuries/illnesses that should exclude the potential participant from the study. This assessment instrument will be administered prior the collection of any anthropometric data. Anthropometric Measurements and Squat Maximum Testing— All anthropometric data will be collected in private (parents or guardians may accompany their child) in the Department of Kinesiology’s Biomechanics Research Station located in the IM Sports Circle Building on the campus of Michigan State University. 0 Weight will be assessed on a standard weight balance while you are wearing shorts and t-shirt. Height will be assessed with a standard anthropometer. Sitting height will be assessed with a standard anthropometer while you are seated on a bench. 0 Segmental lengths will be determined with the use of standard body calipers. Specifically foot, shank, thigh, pelvis, trunk, and head lengths and widths will be assessed. 0 Skinfolds will be used to estimate percent body fat. Specifically, Skinfolds of the triceps, subscapularis (shoulder blade), and chest will be taken. A squat maximum will be assessed after completion of the anthropometric data collection and will also occur at the Biomechanics Research Station. A ten repetition maximum for the parallel squat will be performed. Proper warm up will be performed prior to this test. Experienced spotters will monitor every lift to help prevent injury. Repeated Jump Test- The repeated jump test consists of you performing maximal vertical jumps with your hands on your hips for 1 minute while having one foot on a force platform. This session is separate from the other sessions because you need to be in an unfatigued state to provide a reference of maximal ability. This testing will occur at the Biomechanics Research Station. Workout/Recovery Sessions — These sessions will be used to determine your rate of recovery from performing the different squatting exercises. These sessions will occur at the Biomechanics Research Station in [M Circle, the Biomechanics Gait Lab in West Fee, or a combination of both facilities. The following protocol will be used: 215 You will be asked to perform the exercise in minimal clothing to allow for accurate assessment of body landmarks. Boys will be asked to perform these squat techniques wearing tight fitting (e. g., biker) shorts and either no shirt or an “Under Armor” top. Prior to actual data collection, you will have approximately 15 reflective joint markers affixed to points on the segments of the lower limbs. In addition, you will have a very small portion of your calf, thigh, hamstring, buttocks, and lower back lightly abraded and cleansed in order to affix several surface electromyography (SEMG) electrodes necessary to assess muscle activity of the aforementioned muscles. In order to collect an electromyographic signal that is of high quality, it is important to gently abrade the exposed skin and cleanse with rubbing alcohol to remove any debris that may impede signal quality. Skin preparation and electrode placement will be performed by an investigator of the same sex as the participant. To ensure that the markers and electrodes are placed in the same spot during each workout session, you will be marked with Henne tattoo dye where the markers/electrodes come in contact with the skin. This dye lasts for approximately 2-3 weeks, but will disappear. You will be asked to follow a warm up that should be similar to your normal warm up prior to strength training. You will be asked to perform a maximum vertical jump. You will jump as high as possible and your jump height will be recorded using a You will then perform a workout of either box squats, partial squats, or parallel squats. Experienced spotters will monitor every lift to help prevent injury. Video cameras will be used to determine quantitative and qualitative data with respect to comparing the three different squat techniques. In addition to the video recording of each squat trail, forces applied to the ground will be simultaneously collected via a force platform to assist in the determination of forces that are incurred at the knee and hip joint and also in the lower back. You then will perform the maximal vertical jump again. You will be asked to rest for 3 hours. During this time, a room in 1M Sports Circle will be provided for you to eat, watch movies, read, complete homework, etc. At the end of 3 hours, you will again perform the maximal vertical jump test, and also perform the repeated jump test. A snack may be provided, but we ask that you bring your own lunch if you are tested over a meal time. If you attend a session at IM Circle during the week while parking is enforced, your parking fee will be reimbursed. Please turn in your receipt for your parking to Adam Bruenger who will pay you by check. 216 You are being asked to participate in this study because you have experience with the squatting techniques of interest. After completion of the third workout testing session (the final testing session), you will be given a check for $25 to help defray the cost of gasoline and a T-shirt as thanks for participation in this study. Your participation is totally voluntary, and you may chose to participate or not, as well as to discontinue your participation at any time without any explanation. By participating in this study you agree that the materials and data generated (video, pictures, and measurements) may be used for research and academic purposes. If you do so choose to discontinue participation, all data, including video footage, will be destroyed. You have also been assured that your privacy will be protected to the maximum extent allowable by law. When this research is completed, an abstract of the results will be mailed to you. You may also seek personal data for comparison of the three different squatting techniques. This study consists of activities that you have used in your regular strength training protocols. Thus, the risk for injury during this study is no different than what would be expected during your regular training. Less than maximal weights will be used during the kinematic/kinetic session to lower the chances of a failed attempt and experienced spotters will monitor every lift to help prevent injury. However, there is always a possibility of injury. Possible injuries include muscle strains and injury to the lower back due to the nature of the lifting techniques being used. Though not life threatening, the abraded skin may be discolored for a few days after the testing or even scab. In the unlikely event that you are injured as a result of your participation in this research project, Michigan State University will assist you in obtaining emergency medical care, if necessary, for your research related injuries. If you have insurance for medical care, your medical provider will be billed in the ordinary manner. As with any medical insurance, any costs that are not covered or are in excess of what are paid by your insurance, including deductibles, will be your responsibility. The University’s policy is to not provide financial compensation for lost wages, disability, pain or discomfort, unless required by law to do so. This does not mean you are giving up any legal rights you may have. You may contact Dr. Eugene Brown ino. (517) 353-6491, email: ewbrown@msu.edu, with any questions or to report an injury. If you have any questions about this study, please contact Dr. Eugene Brown ino. (517) 353-6491, email: ewbrown@msu.edu, or Adam Bruenger ino. (517) 432- 4073, email: bruenger@msu.edu at the Department of Kinesiology, Michigan State University. If you have questions or concerns regarding your 1i ghts as a study participant, or are dissatisfied at any time with any aspect of this study, you may contact — anonymously, if you wish- Peter Vasilenko, Ph.D., Director of Human Research Protections, (517)355-2180, fax (517)432-4503, e-mail irb@msu.edu, or regular mail 202 Olds Hall, Michigan State University, East Lansing, MI 48824-1047. 217 Consent Form “Biomechanical and physiological comparison of three methods of back squatting. ” Primary Investigator: Eugene Brown PhD, Department of Kinesiology, Michigan State University Secondary Investigator: Adam Bruenger MS, Department of Kinesiology Michigan State University This study is being conducted as a doctoral dissertation: Name of participant (Print): IF YOU ARE NOT 18 YEARS OF AGE (YOUR 18TH BIRTHDAY HAS NOT OCCURRED PRIOR TO YOUR SIGNING OF THIS FORM), YOU MUST HAVE PARENTAL PERMISSION TO PARTICIPATE. A form will be provided that your parents must fill out and return prior to participating in this study. In addition to the form, an investigator will contact your parents prior to your participation to confirm they understand the nature of the study and your desire to participate. Sign your name below only if you are sure you understand the purpose of this study and are willing to participate in this study. Signature Date Email Phone Birth Date (month/day/year) 218 Video Recording Release Consent/Assent Form Video recordings of you will be made while you participate in aspects of this research project. Additionally, digital photographs may be taken to document the procedures that were used during the project. The informed consent document describes how the video images will be use for this specific study as well as who will have access to the images and where the records will be maintained. The investigators would like your permission to use your video images for purposes outside the study. Please use this form to indicate whether you are willing to allow the use of your images for the purposes described below. Your name will not be associated with your images in any case. You may request to stop the video-taping, or erase any photo or portion of the video, at any time. Should you decide to withdraw from the study, all videotaped sessions and/or photographs of your participation will be deleted and/or destroyed. Y N E O S 1. The videos/photos can be shown to other athletes participating in similar [I E projects. 2. The videos/photos can be used for scientific publications and/or presentations. 3. The videos/photos can be shown in non-scientific publications and /or E] [j presentations. 4. The videos/photos can be shown in classrooms to students. D 1:] Your signature(s) below, indicates that you have read the information and made a decision about how your image may be used. Signature of Participant: ’ Date: Signature of Parent/Guardian: Date: 219 Consent Form “Biomechanical and physiological comparison of three methods of back squatting. Intertester Reliability Form” Primary Investigator: Eugene Brown PhD, Department of Kinesiology, Michigan State University Secondary Investigator: Adam Bruenger MS, Department of Kinesiology Michigan State University F3 This study is being conducted as part of a doctoral dissertation: The purpose of this study is to evaluate the reliability and validity of investigators I who will be performing anthropometric measurements on high school athletes. You are being recruited because you would have similar anthropometric measurements as the population in question. Your participation in this brief investigation will allow us to determine differences in measurement ability of each investigator. Your total time commitment for this study would be approximately 1 hour. You would have the following anthropometric measurements taken by approximately seven individuals. 0 Weight will be assessed on a standard weight balance while you are wearing shorts and t-shirt. Height will be assessed with a standard anthropometer. Sitting height will be assessed with a standard anthropometer while you are seated on a bench. o Segmental lengths will be determined with the use of standard body calipers. Specifically foot, shank, thigh, pelvis, hip, trunk, and head lengths widths will be assessed. 0 Skinfolds will be used to estimate percent body fat. Specifically, Skinfolds of the triceps, pectoralis, and subscapularis (shoulder blade), will be taken. 220 There is no economical benefit from your participation. Your participation is totally voluntary, and you may chose to participate or not, as well as to discontinue your participation at any time without any explanation. By participating in this study you agree that the data generated may be used for research purposes. If you do so choose to discontinue participation, all data will be destroyed. You have also been assured that your privacy will be protected to the maximum extent allowable by law. You will be provided access to your data after completion of study. This study consists of minimal dangers to you. There could be some slight bruising due to multiple Skinfolds taken in the brief amount of time you will be in the study. In the unlikely event that you are injured as a result of your participation in this research project, Michigan State University will assist you in obtaining emergency medical care, if necessary, for your research related injuries. If you have insurance for medical care, your medical provider will be billed in the ordinary manner. As with any medical insurance, any costs that are not covered or are in excess of what are paid by your insurance, including deductibles, will be your responsibility. The University’s policy is to not provide financial compensation for lost wages, disability, pain or discomfort, unless required by law to do so. This does not mean you are giving up any legal rights you may have. You may contact Dr. Eugene Brown ino. (517) 353-6491, email: ewbrown@msu.edu, with any questions or to report an injury. 221 If you have any questions about this study, please contact Dr. Eugene Brown ino. (517) 353-6491, email: ewbrown@msu.edu, or Adam Bruenger ino. (517) 432- 4073, email: brucnger@msu.edu at the Department of Kinesiology, Michigan State University. If you have questions or concerns regarding your rights as a study participant, or are dissatisfied at any time with any aspect of this study, you may contact — anonymously, if you wish- Peter Vasilenko, Ph.D., Chair of the University Committee on Research Involving Human Subjects (UCRHIS) by phone (517) 355-2180, fax: (517) 432-4503, email: ucrihs@msu.edu, or regular mail: 202 Olds Hall, East Lansing, MI 48824. 222 Consent Form “Biomechanical and physiological comparison of three methods of back squatting. Intertester Reliability Form” Primary Investigator: Eugene Brown PhD, Department of Kinesiology, Michigan State University Secondary Investigator: Adam Bruenger MS, Department of Kinesiology Michigan State University This study is being conducted as part of a doctoral dissertation: Name of participant(Print): Sign your name below only if you are sure you understand the purpose of this study and are willing to participate in this study. Name Date 223 APPENDIX B Questionnaires and Data Collection Sheets 224 Questionnaire #1 Contraindications to Participation Participant Name This study requires participants to perform three different back squatting exercises (box, partial, and parallel squats) with considerable weight (approximately 7 0% of maximal weight that can be lifted performing the parallel squat). The performance of . these lifts should be very similar to the techniques that are used in the strength training ‘3 practices at your school. Likewise, the amount of weight used should be similar to what 1r. is experienced during training. Therefore, the risk of injury during this study should be the same as during your normal strength training. However, all strength training exercises have some inherent risk of injury that increases if other injuries are present. This questionnaire will be used to determine if you have any contraindications that b l- should exclude you from participation in this study. 1. Are you currently performing box squat and parallel squat exercises in your strength training program? YES NO If NO: Have you ever performed box squats and parallel squat exercises in your strength training program? YES NO 1 Please also explain why you are not currently performing these exercises i in your program. 1 2. How long (to the nearest month) have you performed these two lifts: a. Box Squats b. Parallel Squats Participant (Signature) Date 225 Questionnaire #1 Contraindications to Participation To be filled out by the participant’s parent or guardian This study requires participants to perform three different back squatting exercises (box, partial, and parallel squats) with considerable weight (approximately 70% of maximal weight that can be lifted performing the parallel squat). The performance of these lifts should be very similar to the techniques that are used in the strength training practices at your child’s school. Likewise, the amount of weight used should be similar to what is experienced during training. Therefore, the risk of injury during this study should be the same as during your child’s normal strength training. However, all strength training exercises have some inherent risk of injury that increases if other injuries are present. This questionnaire will be used to determine if your child has any contraindications that should exclude him from participation in this study. Participant Name 1. Has your child had a physical in the last year clearing him to train and participate in sports (if your child has participated in sports this year, he must have one on record at you school)? YES NO If NO, please explain 2. Is your child currently under a physician’s/coach’s/athletic trainer’s orders to not perform squatting exercises in his strength training program? YES NO If YES, please explain: 3. Has your child ever been under a physician’s/coach’s/athletic trainer’s orders to not perform squatting exercises in his strength program? YES NO If YES, please explain and state when he was allowed to start squatting again: 226 4. Has your child had any of the following injuries: YES NO IF YES, please circle which of the following have occurred and indicate how long ago these injuries occurred. Torn ligaments of the ankle Torn ligaments of the knee (ACL, PCL, MCL, LCL) Damaged meniscus Injury to the spine Hernia Broken bone of the lower extremity Injuries to the shoulder/arm/hand that have affected his lifting technique Any other injury that you feel may affect your child’s ability to perform the box, partial, or parallel squat? (List injury/injuries and when they occurred) This information is accurate to the best of my knowledge. Parent or Guardian (Signature) Date 227 Questionnaire #1 (Consent version for college students over 18 years of age) Contraindications to Participation This study requires participants to perform three different back squatting exercises (box, partial, and parallel squats) with considerable weight (approximately 70% of maximal weight that can be lifted performing the parallel squat). The performance of these lifts should be very similar to the techniques that are used in the strength training practices at your school. Likewise, the amount of weight used should be similar to what is experienced during training. Therefore, the risk of injury during this study should be the same as during your normal strength training. However, all strength training exercises have some inherent risk of injury that increases if other injuries are present. This questionnaire will be used to determine if you have any contraindications that should exclude you from participation in this study. Participant Name 1. Have you had a physical in the last year clearing you to train and participate in sports? YES NO If NO, please explain 2. Are you currently under a physician’s/coach’s/athletic trainer’s orders to not perform squatting exercises in your strength training program? YES NO If YES, please explain: 3. Have you ever been under a physician’s/coach’s/athletic trainer’s orders to not perform squatting exercises in your strength program? YES NO If YES, please explain and state when you were allowed to start squatting again: 228 4. Have you had any of the following injuries: YES NO IF YES, please circle which of the following have occurred and indicate how long ago these injuries occurred. Torn ligaments of the ankle Torn ligaments of the knee (ACL, PCL, MCL, LCL) Damaged meniscus Injury to the spine Hernia Broken bone of the lower extremity Injuries to the shoulder/arm/hand that have affected your lifting technique Any other injury that you feel may affect your ability to perform the box, partial, or parallel squat? (List injury/injuries and when they occurred) This information is accurate to the best of my knowledge. Participant Signature Date 229 Questionnaire #2 Pre-Testing Survey Participant # 1. How many hours of sleep did you have last night? 2. Have you engaged in any of the following activities in the last 48 hours? a. Weight training of the legs and lower back YES NO b. A competitive sporting event such as YES NO basketball, soccer, football, etc. that lasted more than 20 minutes? c. An endurance activity YES NO (running, riding a stationary cycle, swimming) that lasted more than 20 minutes? 3. Since the last time you were tested for this study, have you had any injuries (ankle or knee sprains or other injury, ankle or knee pain, lower back pain or other injury to the lower back, broken bones, etc.) or illnesses that would prevent you from completing today’s testing or could possibly keep you from performing at your optimal level? YES NO If YES, please explain 230 Biomechanical and physiological comparison of three methods of back squatting. Participant # Date Birth Date Anthropometric Measurements Weight kg Standing Height cm Seated Height CITI Segment Lengths/Widths/Girths Width ,. _ Circumference Foot . .-.~ ‘i - '7]! éi’TE?;._:* W1 Ankle Bottomof'ittto " ' Maueolous ' g I j ‘ i _. Shank Thigh Pelvis ASIS Trunk 231 Biomechanical and physiological comparison of three methods of back squatting. Participant # Date Warm up: 5 min cycle ergometer (comfortable pace 50-60 rpm) Stretches: 30 seconds each (see sheet) 1. Calf 2. Quad 3. Spinal twist 4. Hip F lexor 5. Groin 6. Hurdler Let stretch briefly on own Reference Depths Height From Reference Parallel cm cm Box cm cm Partial cm cm Sflat Maximums Parallel lb Warm up 1 50% (10 reps) 1 minute rest Warm up 2 75% (5 reps) 2 minutes rest Warm up 3 85% (5 reps) 3 minutes rest lSt Attempt 3-5 minutes rest between 2'“I Attempt 3-5 minutes rest between 3rd Attempt 3-5 minutes rest between 4’h Attempt 3-5 minutes rest between 232 Session 3-5 tests Date Start Time of Prep Subject # Session Workout Subject Weight Squat Depth Position Parallel Depth Position Time Finished with Prep Pre-Workout Jumps Reach Height VJ#l VJ#2 VJ#3 Time Left Bio Lab Marker Notes on Back Weight to Use for Workout Shoulder Location (in cm) X=Medial Lateral Y=Anterior Posterior Z=Cephalo Caudal X_____ Y_____ Z RPE Set 1 (Rate your effort) Set 1 (Rate your effort) Set 1 (Rate your effort) Overall Workout (Rate your overall workout) Time Left Gait Lab Time at Bio Lab Post 15 VJ#l VJ#2 VJ #3 Performed at Start Second Warm Up at Post 3 Hours VJ#l VJ#2 VJ #3 Bosco Height Location off Force Plate Save As 233 APPENDIX C Inter- and Intratester Evaluation of Anthropometric Measurements 234 The secondary investigator evaluated his skill performing the anthropometric measurements made in this study. Four college aged male participants volunteered for this study. These participants had anthropometric builds similar to the desired research population and were a sample of convenience. The participants read and signed a consent form approved by the Michigan State University Institutional Review Board prior to participation (Appendix A). Participants were measured by the secondary investigator (tester l) and a former Michigan State University Professor (tester 2) who was considered an expert in performing anthropometric measurements. Two participants were first measured by tester 1 while the other two were first measured by tester 2. The testers then switched participants. Finally, all participants were remeasured by tester l. Inter- and intratester reliability were evaluated by performing intraclass correlation coefficients (ICC) for each participant. The results of the measurements and ICC values are provided in Tables 34-35. 235 Table 34 Inter- and Intratester Comparisons Participant Measurement Tester 1 Pre Tester 1 Post Tester 2 Participant 1 Weight (cm) 63.5 63.6 63.6 Height (kg) 169.5 169 169.7 Standing Height (cm) 86.7 86.5 87.5 Foot Length (cm) 24.4 24.3 25 Foot Width (cm) 8.8 9.1 9.2 Ankle Width (cm) 6.5 6.5 6.9 Shank Length (cm) 42 39.9 40.3 Knee Width (cm) 9 8.9 9.5 Thigh Length (cm) 45.8 45.4 45.7 Pelvis Width (cm) 28.1 27 27.9 ASIS Breadth (cm) 26.4 25.5 26.9 Trunk Width (cm) 37 37 39.3 Trunk Length (cm) 41.8 38.5 37.6 Participant 2 Weight (cm) 60.4 60.4 60.7 Height (kg) 163.5 163.7 163.4 Standing Height (cm) 86.5 86.3 86.7 Foot Length (cm) 24.5 24.7 24.6 Foot Width (cm) 9.6 9.2 9.7 Ankle Width (cm) 6.8 6.7 6.8 Shank Length (cm) 39 38.3 38.7 Knee Width (cm) 9 9.1 9.1 Thigh Length (cm) 45.5 48.5 44.4 Pelvis Width (cm) 26.5 26 27.4 ASIS Breadth (cm) 24.5 23 24.8 Trunk Width (cm) 38.5 38.5 39 Trunk Length (cm) 37.7 37.8 38.6 236 Table 34 Continued Participant Measurement Tester 1 Pre Tester 1 Post Tester 2 Participant 3 Weight (cm) 61.3 61.2 61.25 Height (kg) 166 166 165.7 Standing Height (cm) 85.6 86 86.2 Foot Length (cm) 24.5 23.9 24.3 Foot Width (cm) 9.2 9.8 9.6 Ankle Width (cm) 7.2 7.2 7.7 Shank Length (cm) 40.4 39.3 39.3 Knee Width (cm) 9.4 9.5 9.6 Thigh Length (cm) 43.6 38 45.9 Pelvis Width (cm) 26.2 26.5 27.7 ASIS Breadth (cm) 24.5 24.5 26.2 Trunk Width (cm) 40.1 40 39.8 Trunk Length (cm) 38 33.7 36.9 Participant 4 Weight (cm) 68.6 68.8 69 Height (kg) 155.1 155 155.3 Standing Height (cm) 83.2 83.2 83.6 Foot Length (cm) 24.5 24.4 24.7 Foot Width (cm) 9.6 9.8 9.5 Ankle Width (cm) 6.8 6.6 6.5 Shank Length (cm) 34.2 34.7 36.7 Knee Width (cm) 9.3 9.1 9.2 Thigh Length (cm) 38.7 39.2 36 Pelvis Width (cm) 25.5 26.1 25.5 ASIS Breadth (cm) 24 23 23.6 Trunk Width (cm) 39.4 39.5 40.2 Trunk Length (cm) 36 36 37.3 237 Table 35 Intraclass Correlation Coefficients for Inter- and Intratester Reliability Participant 1 Participant 2 Participant 3 Participant 4 Intertester Reliability (R) .99 .99 .99 .99 Intratester Reliability (R) .99 .99 .99 .99 238 APPENDIX D Order of Workout Sessions 239 Table 36 Random Assigned Orders of Workouts Order Session 1 Session 2 Session 3 1 Parallel Partial Box 2 Parallel Box Partial 3 Partial Parallel Box 4 Partial Box Parallel 5 Box Parallel Partial 6 Box Partial Parallel 240 APPENDIX E Squat Model Validation 241 A five segment, quasi-static model was created using BodyBuilder software (Vicon, Los Angeles, CA). Two steps were taken to verify that the BodyBuilder program provided valid results. First, a simpler model, that assumed that each segment was mass- less and there were no inertial forces, was evaluated. This model confirmed that the reactive forces (horizontal and vertical) at each of the joints (ankle, knee, and hip) were the same when segment masses and inertial forces and moments were ignored. Second, the quasi-static model was evaluated. This model added in the segment masses but still did not account for inertial forces and moments. The BodyBuilder prograrn’s reported vertical and horizontal joint reaction forces and segment weights were summed in Excel (Microsoft, Redmond, WA) to confirm that they added up to zero. The reaction moment at each joint was also calculated in Excel using the formulas outlined in the Data Analysis section of the methods chapter. The Excel calculations used the BodyBuilder reported forces and segment position data. The Excel calculated values and the Bodybuilder reported values were compared for several trials at multiple instances to confirm that the values were the same. One set of results of the summed forces and the Excel calculated moments compared to the BodyBuilder reported moments for one time frame for one participant are provided in Tables 37-38 as an example. These represent typical results when the BodyBuilder values were compared to Excel calculations. The two instances provided were chosen to show the values when a participant was in contact with only one force platform (i.e., the parallel example) and when the participant was in contact with both force platforms (the box example). Low back forces and moments are not reported because these forces and moments were not calculated using the BodyBuilder model, but were calculated in Excel using the formulas outlined in the Data 242 Analysis section of the methods chapter. Excel calculations were used instead of the BodyBuilder software to calculate low back moments because the BodyBuilder software could not calculate both the hip moment about the virtual hip point and also the lower back moment about the greater trochanter. Table 37 Summation of Reaction Forces for a Single Participant at One Given Time Frame Joint Workout Condition Total Ankle Parallel Z forces Y (N) 0.0 2 forces Z (N) 0.0 Box* 2 forces Y (N) 0.0 E forces Z (N) -0.14 Eng Parallel E forces Y (N) 0.0 X forces Z (N) 0.01 Box 2 forces Y (N) 0.0 2 forces Z (N) -0.4 flip Parallel 2 forces Y (N) 0.0 2 forces Z (N) 0.03 Box 2 forces Y (N) 0.0 2 forces Z (N) -1.01 *=The instant chosen for evaluation of the box squat was a Boxl (participant sitting on section. 243 the box and starting to move forward) condition as described in the results Table 38 Comparison of BodyBuilder Joint Moment Values to Excel Calculations Joint Workout Condition BodyBuilder Excel Ankle Parallel Reaction moment (Nm) -71.252 -70.433 Normalized Reaction -1.08 -1.07 moment (Nm/kg) Box* Reaction moment (Nm) -.729 -2.040 Normalized Reaction -.Ol -.03 moment (Nm/kg) @ Parallel Reaction moment (Nm) 78.34 78.18 Normalized Reaction 1.17 1.17 moment (Nm/kg) Box Reaction moment (Nm) 9.298 9.306 Normalized Reaction 1.39 1.39 moment (Nm/kg) Hip Parallel Reaction moment (Nm) -203 -203.7 Normalized Reaction -3.03 -3.04 moment (Nm/kg) Box Reaction moment (Nm) -6.634 -6.503 Normalized Reaction -.O99 -.097 moment (Nm/kg) *=The instant chosen for evaluation of the box squat was a Boxl (participant sitting on the box and starting to move forward) condition as described in the results section. 244 As can be seen in Tables 37, there were some differences in expected summed force values (all should have added up to zero). Additionally, there were minor differences in calculated moments from the two methods. Overall, there is very good agreement between the BodyBuilder reported values and the Excel calculated values. There is minimal disagreement for the ankle moment calculations (Table 38). Differences are most likely due to not knowing: (a) where the BodyBuilder software rounds force platform, body segment weight, and marker position data when it performs its calculations and (b) where the BodyBuilder software attaches the horizontal reaction force to the foot. These problems are more prominently observed in the box squat where the vertical forces are minimal and the horizontal forces contribute more to the overall moment at the ankle. However, the differences (.02 Nm/kg) in BodyBuilder values and Excel calculated values at the ankle are minimal compared to the difference between the box squat and parallel squat moments at the ankle (1.04 Nm/kg). The moments at the knee and hip all show similar results to the ankle. More perplexing is why the forces do not always add up to zero. One possible explanation is that the BodyBuilder software first calculated the reactive forces about the locally defined axes of each segment and then converts these forces to the global reaction force values. This could possibly causes differences in rounding when also accounting for the included segment masses. Although these errors must be acknowledged, overall, they are minimal when compared to the typical forces experienced (e.g., 1 N difference when the total vertical forces are approximately 800 N). 245 BodyBuilder Models Model I .' Static Measurement Model {*Static No Bar Segment Check*} {*Orthopaedic Biomechanics Laboratories -- Gait Analysis Laboratory*} {*Written by Adam Bruenger*} {*Use with BodyBuilder*} {*Use with Official.mkr*} {*Use with any subj ect.mp*} Macro Axes(segment,axislength) {* This macro creates segment axes for display purposes*} segment#o= {0,0,0} *segment segment#x= {axislength,0,0} *segment segment#y= {0,axislength,0} *segrnent segment#z= {0,0,axislength} *segrnent output (segment#o,segment#x,segment#y,segment#z) endmacro {* *} {*Macro Filter procedure, Low pass digital filter“) MACRO Filter (Pararn, F 1) F] = (param[-2] + 3*param[-l] + 4*param[0] + 3*param[1] + param[2])/ 12 ENDMACRO {*Filter Procedure. Weighted Average Filter*} 1* *} Filter (JNO, JNO) Filter (XIP,XIP) Filter (RSIC,RSIC) Filter (RASIS,RASIS) Filter (SAC,SAC) Filter (RGTR,RGTR) Filter (RAMT,RAMT) Filter (RLMT,RLMT) Filter (RLKJ,RLKJ) ' Filter (RLSHA,RLSHA) Filter (RASHA,RASHA) 246 Filter (RLMA,RLMA) Filter (RCAL,RCAL) Filter (R2MH,R2MH) Filter (R5MH,R5MH) {*Define Offset Points*} {* *} {*Deflne reference segements so that we can create local offsets*} MidThigh={1(RAMT),2(RLMT),3(RLMT)} FOOT=[R2MH,RLMA-R2MH,RLMA-RLKJ,yxz] SHANK=[RLMA,RLKJ-RLMA,RLMA-R2MH,zxy] THIGH=[RLKJ,RLKJ-MidThigh,RLKJ-RLMA,zxy] PELVIS=[RGTR,RGTR-RSIC,RGTR-RLKJ,zxy] {*FIND ALL STATIC OFFSETS AND WRITE TO MP FILE FOR USE IN OTHER TRIALS*} If $Static ==l Then $%SHANK=dist(RLKJ,RLMA) hipcheck1=RGTR-RLKJ $%hipcheck1 =hipcheck1 (3) hipcheck3=RLMT-RLKJ $%hipcheck3=2(hipcheck3) $%hipcheck4=3(hipcheck3) $%hipcheck5=$%hipcheck3*$%hipcheckl/$%hipcheck4 $%hipcheck2= {O,$%hipcheck5 ,$%hipcheck3 } $%hipoffset={0,-12.4,435} $%THIGH=dist(RGTR,RLKJ) $%PELVIS=dist(RSIC,RGTR) anklecheck= $%ankleoffset=90- 1 (anklecheck) $%kneecheck= $%kneeo ffset=1 80-1($%kneecheck) $%pelvischeck= $%pelvisoffset=l 80-1($%pelvischeck) output($%hipoffset) PARAM($%hipcheck1, $%hipcheck2,$%hipcheck3,$%SHANK, $%THIGH, $%PELVIS, $%pelvisoffset) PARAM($%kneecheck, $%ankleoffset, $°/okneeoffset, $%pelvischeck, $%hipoffset) Endif 247 Model 2: Dynamic Analysis Model *SQUAT QUASTI STATIC FULL BODY SIMPLE VERSION (2 D MODEL)*} {*Orthopaedic Biomechanics Laboratories -- Gait Analysis Laboratory*} {*Written by Adam Bruenger*} {*Use with BodyBuilder*} {*Use with Squatfinal.mkr*} {*Use with Squatfinal.mp*} {*Start of macro section*} {* *} Macro REPLACE4(pl ,p2,p3,p4) {*Replaces any point missing from set of four fixed in a segment*} 5234 = [p3,p2-p3,p3-p4] {*Defines a segment S234 using all points except p1*} p1V = Average(p1/3234)*3234 {*Finds the average position of p1 in the 3234 local Co-ord system and creates virtual point pr from this reference system*} 5341 = [p4,p3-p4,p4-p1] {*Defines a segment s341 using all points except 122*} p2V = Average(p2/s34l)*s34l {*Finds the average position of p2 in the 5341 local Co-ord system and creates virtual point p2V from this reference system*} 3412 = [p1,p4—p1,p1-p2] {*Defines a segment S412 using all points except p3*} p3V = Average(p3/s412)*s412 { *Finds the average position of p3 in the 3412 local Co-ord system and creates virtual point p3V from this reference system*} s123 = [p2,p1-p2,p2-p3] {*Defines a segment 5123 using all points except 124*} p4V = Average(p4/3123)*5123 {*Finds the average position of p4 in the 5123 local Co-ord system and creates virtual point p4V from this reference system*} {* Now only replaces if original is missing 11-99 *} p1 =pl ? pr p2 = p2 ? p2V p3 = p3 ? p3V p4 = p4 ? p4V endmacro Macro Axes(segment,axislength) {* This macro creates segment axes for display purposes*} segment#o= {0,0,0} *segment segment#x= {axislength,0,0} *segment segment#y= {0,axislength,0} *segment segment#z= {0,0,axislength} *segment 248 output (segment#o,segment#x,segment#y,segment#z) endmacro {* *1 {*Macro Filter procedure, Low pass digital filter*} MACRO Filter (Param, F1) F1 = (param[-2] + 3*param[-1] + 4*param[0] + 3*param[1] + param[2])/12 ENDMACRO {*Filter Procedure. Weighted Average F ilter*} {* *} Filter (EBAR,EBAR) Filter (JNO, JNO) Filter (XIP,XIP) Filter (RSIC,RSIC) Filter (SAC,SAC) Filter (RGTR,RGTR) Filter (RAMT,RAMT) Filter (RLMT,RLMT) Filter (RLKJ,RLKJ) Filter (RLSHA,RLSHA) Filter (RASHA,RASHA) Filter (RLMA,RLMA) Filter (RCAL,RCAL) Filter (R2MH,R2MH) Filter (R5MH,R5MH) {*Virtual Points*} REPLACE4 (R2MH,R5MH,RCAL,RLMA) REPLACE4 (RLMA,RLSHA,RASHA,RLKJ) REPLACE4 (RLKJ,RLMT,RAMT,RGTR) {*Define Offset Points*} {* *} {*Define reference segements so that we can create local offsets*} G0={0,0,0} GX= { 1 0,0,0} GY= {0,10,0} GZ={0,0,10} GLOBAL=[G0,GZ—G0,GY-G0,zxy] RSHO = ebar+ { $ShoulderOffest1 ,$ShoulderOffest2,$ShoulderOffest3} 249 MidThigh={ 1(RAMT),2(RLMT),3(RLMT)} RF OOT=[R2MH,RLMA-R2MH,RLMA-RLKJ,yxz] RSHANK=[RLMA,RLKJ-RLMA,RLMA-R2MH,zxy] RTHIGH=[RLKJ,RLKJ-MidThigh,RLKJ-RLMA,zxy] RPELVIS=[RGTR,RSHO-RGTR,RGTR-RLKJ,zxy] {*Repositions ponits in Global frame*} HIP=-$%hipoffset*RTHIGH PELVISTOP= {0,0,$%PELVIS} *RPELVIS PELVISTOP2= {0,0,.895 *$%PELVIS} *RPELVIS LHIP=HIP+ {$AsisBreadth,0,0} shank=dist(RLKJ,RLMA) Output(PELVISTOP2, PELVISTOP, MidThigh, RSHO,HIP, LHIP) {*COM for segments*} comf=(RLMA+R2MH)/2 coms=RLMA+(RLKJ-RLMA)*.567 comt=RLKJ+(HIP-RLKJ)*.567 OUTPUT(comf,coms, comt) {*angles* } anklejoint= {*adjust for markers not being perfectly at 90 degrees*} anklecorrect=$%ankleo ffset+l (anklej oint) anklejoint= kneej oint= kneecorrect=$ %kneeo ffset+1 (kneej oint) kneejoint= hipjoint= hipj oint2= hipj oint2correct=90-1 (hipj oint2) hipjoint2= OUTPUT(anklejoint,kneejoint, hipjoint,hipjoint2) 250 {*Forceplate Data*} if EXIST( ForcePlate] ) Forcel = ForcePlate1(1) Momentl = ForcePlate l (2) Centrel = ForcePlate1(3) if( ABS ( Forcel )> 10) Pointl = Centrel + {-Moment1(2)/Forcel(3), Moment1(1)/Force1(3), -Centre1(3) } else Pointl = Centrel endif Forcel = Forcel + Pointl OUTPUT ( Pointl, Forcel , Centrel , Momentl ) endif if EXIST( ForcePlate2 ) F orce2 = ForcePlate2(l) Moment2 = ForcePlate2(2) Centre2 = F orcePlate2(3) if( ABS ( Forcel )> 10) Pointl = CentreZ + {~Moment2(2)/Force2(3), Moment2(l)/Force2(3), -Centre2(3) } else Point2 = Centre2 endif F orce2 = F orce2 + Point2 OUTPUT ( Point2, Force2, Centre2 , Moment2 ) endif {*Kinetics*} AnthropometricData DEFAULTTORSO 0 DEFAULTPELVIS 0 DEFAULTTHIGH O DEFAULTSHANK 0 DEFAULTFOOT 0 OOOOO OOOOO OOOOO EndAnthropometricData $%footforce=-$BodyMass*.0145 *9. 81 $%shankforce=-$BodyMass* .0465 *9.81 $%thighforce==—$BodyMass* . 1 00*9. 81 $%pelvisforce=~$BodyMass"‘. 1 42*9. 81 251 JIlll-Illltl . Param($%footforce, $%shankforce, $%thighforce,$%pelvisforce) {*Build the kinetic hierarchy with the kinetic data for each segment*} {*foot mass/force using assumptions of dempters data *} dummyforce= {0,0,$%footforce} dummymoment= {0,0,0} dummyapplication={comf(1),comf(2),comf(3)} reactionforce=|dummyforce,dummymoment,dummyapplication| LRF=reactionforc e/RFOOT CONNECT(RFOOT,reactionforce,1 ) {*shank mass/force using assumptions of dempters data *} dummyforce2= { 0,0,$°/oshankforce} dummymoment2= { 0,0,0} dummyapplication2={coms(l),coms(2),coms(3)} reactionforce2=|dummyforce2,dummymoment2,dummyapplication2| CONNECT(RSHANK,reactionforce2, l ) {*thigh mass/force using assumptions of dempters data *} dummyforce3={0,0,$%thighforce} dummymoment3={0,0,0} dummyapplication3={comt(1),comt(2),comt(3)} reactionforce3=|dummyforce3,dummymoment3,dummyapplication3l CONNECT(RTHIGH,reactionforce3, 1 ) {*Pelvis mass/force using assumptions of dempters-get info and fill in*} dummyforce4={0,0,$%pelvisforce} dummymoment4= {0,0,0} dummyapplication4={PELVISTOP2(1),PELVISTOP2 (2),PELVISTOP2 (3)} reactionforce4=Idummyforce4,dummymoment4,dummyapplication4| CONNECT(RPELVIS,reactionforce4, l ) CONNECT(RPELVIS,ForcePlateZ,1) RPELVIS=[RPELVIS,DEFAULTPELVIS] RTHIGH=[RTHIGH,RPELVIS,HIP,DEFAULTTHIGH] RSHANK=[RSHANK,RTHIGH,RLKJ,DEFAULTSHANK] RFOOT=[RFOOT,RSHANK,RLMA,DEFAULTFOOT] =REACTION(RFOOT) KF=REACTION(RSHANK) HF=REACTION(RTHIGH) 252 GAF=AF*RFOOT GKF=KF* RSHANK GHF=HF* RTHIGH ankleforce=GAF(1 ) anklemoment=GAF(2) ankleforceeval=ankleforce/$BodyMass anklemomenteval=(anklemoment/SBodyM ass)/ 1 000 kneeforce=GKF( 1 ) kneemoment=GKF(2) kmomentcorrect=( 1 (kneemoment)- 1 (anklemoment))*$%SHANK/shank+l (anklemoment) kneeforceeval=kneeforce/$BodyMass kneemomenteval=(kmomentcorrect/$BodyMass)/1 000 hip force=GHF( 1 ) hipmom ent=GHF(2) hmomementcorrect=(1 (hipmoment)+kmomentcorrect-1 (kneemoment)) hipforceeval=hipforce/$BodyMass hipmomenteval=(hmomementcorrect/$BodyM ass)/ 1 000 {*Account for Left Leg for the Torso*} dummylefthipforce= {hipforce( l ),-hipforce(2),-hipforce(3)} dummylefthipmoment= {-hipmoment( 1 ),~hipmoment(2),-hipmoment(3)} dummylefthipapplication={LHIP(1),LHIP(2),LHIP(3)} reactionforceleftHIP=|dummylefthipforce,dummylefthipmoment,dummylefthipapplicatio n| LHRF=reactionforceleftHIP/RTHIGH CONNECT(RPELVIS,reactionforceleftHIP, 1 ) LBF=REACTION(RPELVIS) GLBF=LBF*RPELVIS lbforce=GLBF( l ) lbmoment=GLBF(2) lbmomentcorrect=(1 (lbmoment)-2 * 1 (hipmoment)+2*hmomementcorrect) lbforceeval=1bforce/SB0dyMass lbmomenteval=(1bmomentcorrch$BodyMass)/ 1 000 OUTPUT(AF,KF,HF,LBF) OUTPUT(ankleforce, anklemoment, kneeforce, kneemoment, krnomentcorrect, hipforce, hipmoment,hmomementcorrect, lbmoment,reactionforceleftHIP,lbforce) OUTPUT(ankleforceeval,anklemomenteval,kneeforceeval,kneemomenteval,hipforceeva1, hipmomenteval,lbforceeval,lbmomenteval) 253 BIBLIOGRAPHY 254 BIBLIOGRAPHY Adams, M. A., & Hutton, W. C. (1985). The effect of posture on the lumbar spine. Journal of Bone & Joint Surgery -British Volume, 67(4), 625-629. Anderson, G. B. J ., & McNeil, T. W. (1989). Lumbar spine syndromes: Evaluation and treatment. New York, NY: Springer-Verlag. Andersson, B. J ., Ortengren, R., Nachemson, A., & Elfstrom, G. (1974a). Lumbar disc pressure and myoelectric back muscle activity during sitting. I. Studies on an experimental chair. Scandinavian Journal of Rehabilitation Medicine, 6(3), 104- 1 14. Andersson, B. J ., & Ortengren, R. (1974b). Lumbar disc pressure and myoelectric back muscle activity during sitting. 11. Studies on an office chair. Scandinavian Journal of Rehabilitation Medicine, 6(3), 115-121. Andersson, B. J ., & Ortengren, R. (1974c). Lumbar disc pressure and myoelectric back muscle activity during sitting. 3. Studies on a wheelchair. Scandinavian Journal of Rehabilitation Medicine, 6(3), 122-127. Andersson, B. J ., Ortengren, R., Nachemson, A., & Elfstrom, G. (1974d). Lumbar disc pressure and myoelectric back muscle activity during sitting. IV. Studies on a car driver's seat. Scandinavian Journal of Rehabilitation Medicine, 6(3), 128—133 Andrews, J. G., Hay, J. G., & Vaughan, C. L. (1983). Knee shear forces during a squat exercise using a barbell and a weight machine. Paper presented at the Biomechanics VIII: Proceedings of the Eighth International Congress of Biomechanics, Nagoya, Japan. Arthur, M. J ., & Bailey, B. L. (1998). Complete conditioning for football. Champaign, IL: Human Kinetics. Baechle, T. R., & Earle, R. W. (2000). Essentials of strength training and conditioning. Champaign, IL: Human Kinetics. Barnett, C., Kippers, V., & Turner, P. (1995). Effects of variations of the bench press exercise on the EMG activity of five shoulder muscles. Journal of Strength & Conditioning Research, 9(4), 222-227. Bosco, C., Colli, R., Bonomi, R., Von Duvillard, S. P., & Viru, A. (2000). Monitoring strength training: neuromuscular and hormonal profile. Medicine & Science in Sports & Exercise, 32(1), 202-208. 255 Bosco, C., Luhtanen, P., & Komi, P. V. (1983). A simple method for measurement of mechanical power in jumping. European Journal of Applied Physiology and Occupational Physiology, 50(2), 273-282. Brown, E. W. (2004). Anthropometric measurements. Unpublished manuscript. Brown, E. W., & Abani, K. (1985). Kinematics and kinetics of the dead lift in adolescent power lifters. Medicine & Science in Sports & Exercise, 1 7(5), 554-566. Brown, L. (1998). Point/Counterpoint: Box squats for high school athletes. Strength and Conditioning, 20(6), 21. Brown, L. (2003). Point/Counterpoint: Performance box squats. Strength and Conditioning, 25(1), 22-23. Campbell, D. (1967). Maintenance of strength training during a season of sports participation. American Corrective Therapy Journal, 21, 193-195. Cappozzo, A., F elici, F ., Figura, F., & Gazzani, F. (1985). Lumbar spine loading during half-squat exercises. Medicine & Science in Sports & Exercise, 1 7(5), 613-620. Caterisano, A., Moss, R. F ., Pellinger, T. K., Woodruff, K., Lewis, V. C., Booth, W., et al. (2002). The effect of back squat depth on the EMG activity of 4 superficial hip and thigh muscles. Journal of Strength & Conditioning Research, 16(3), 428-432. Chaffin, D. B., Anderson, G. D. B., & Martin, B. J. (1999). Occupational biomechanics. New York: J. Wiley & Sons, Inc. Chandler, T. J ., & Stone, M. H. (1991). NSCA Position Paper: The squat exercise in athletic conditioning: A position statement and review of the literature. National Strength and Conditioning Association Journal, 13(5), 51-58. Cholewicki, J ., McGill, S. M., & Norman, R. W. (1991). Lumbar spine loads during the lifting of extremely heavy weights. Medicine & Science in Sports & Exercise, 23(10), 1179-1186. Clemons, J. M., & Aaron, C. (1997). Effect of grip width on the myoelectric activity of the prime movers in the bench press. Journal of Strength & Conditioning Research, 11(2), 82-87. Cogley, R. M., Archarnbault, T. A., Fibeger, J. F ., Koverrnan, M. M., Youdas, J. W., &‘ Hollman, J. H. (2005). Comparison of muscle activation using various hand positions during the push-up exercise. Journal of Strength & Conditioning Research, 19(3), 628-633. 256 Cohen, J. (1988). Statistical power analysis for behavioral sciences. Hillsdale, NJ: E. Erlbaum Associates. Corder, K. P., Potteiger, J. A., Nau, K. L., Figoni, S. F., & Hershberger, S. L. (2000). Effects of active and passive recovery conditions on blood lactate, rating of perceived exertion, and peforrnance during resistance exercise. Journal of Strength & Conditioning Research, 14(2), 151-156. Day, M. L., McGuigan, M. R. M., Brice, G., & Foster, C. (2004). Monitoring exercise intensity during resistance training using the session RPE scale. Journal of Strength & Conditioning Research, 18(2), 353-358. Ebben, W. P., & Jensen, R. L. (2002). Electromyographic and kinetic analysis of traditional, chain, and elastic band squats. Journal of Strength & Conditioning Research, 16(4), 547-550. Escamilla, R. F., Fleisig, G. S., Zheng, N., Barrentine, S. W., Wilk, K. E., & Andrews, J. R. (1998). Biomechanics of the knee during closed kinetic chain and open kinetic chain exercises. Medicine &. Science in Sports & Exercise, 30(4), 556-569. Escamilla, R. F., F leisig, G. S., Zheng, N., Lander, J. E., Barrentine, S. W., Andrews, J. R., et a1. (2001). Effects of technique variations on knee biomechanics during the squat and leg press. Medicine & Science in Sports & Exercise, 33(9), 1552-1566. Escamilla, R. F., Lander, J. E., & Garhammer, J. (2000). Biomechanics of powerlifting and weightlifting exercises. In W. E. Garrett, Jr., & D. Kirkendall (Eds), Exercise and Sport Science. Philadelphia, PA: Lippincott Williams & Wilkins. Escamilla, R. F., Francisco, A.C., Fleisig, G. S., et al. (2000). A three dimensional biomechanical analysis of the sumo and conventional style deadlifts. Medicine & Science in Sports & Exercise, 32(7), 1265-1275. Faigenbaum, A. D., & Micheli, M. D. (1998). Youth strength training. Retrieved March 20, 2005, from www.acsm.org. Fleck, S., & Kraemer, W. (2004). Designing resitance trainining programs (3rd ed. ). Champaign, IL: Human Kinetics. Foster, C., F lorhaug, J. A., Franklin, J ., Gottschall, L., Hrovatin, L. A., Parker, 8., et a1. (2001). A new approach to monitoring exercise training. Journal of Strength & Conditioning Research, 15(1), 109-115. Fry, A. G, Am, T. A., Bauer, J. A., & Kraemer, W. J. (1993). A comparison of methods for determining kinematic properties of three barbell squat exercises. Journal of Human Movement Studies, 24, 83-95. 257 Fry, A. C., Smith, J. C., & Schilling, B. K. (2003). Effect of knee position on hip and knee torques during the barbell squat. Journal of Strength & Conditioning Research, 1 7(4), 629-633. Gearhart, R. F ., Goss, F. L., Lagally, K. M., Jakicic, J. M., Gallagher, J ., & Robertson, R. J. (2001). Standardized scaling procedures for rating perceived exertion during resistance exercise. Journal of Strength & Conditioning Research, 15(3), 320- 325. Glass, S. C., & Armstrong, T. (1997). Electromyographical activity of the pectoralis muscle during incline and decline bench presses. Journal of Strength & Conditioning Research, 11(3), 163-167. Goel, V. K., & Weinstein, J. N. . (1990). Biomechanics of the spine: Clinical and surgical perspective. Boca Raton, FL: CRC Press. Goss, K. (2004). Let's Talk Box Squat. March 26, 2005, from hm)://www.bigerfasterstronger.com/p magPrint.asp?id=l 39. Granhed, H., Jonson, R., & Hansson, T. (1987). The loads on the lumbar spine during extreme weightlifting. Spine, 12, 146-149. Hamill, J. K., & Knutzen, K. M. (1995). Biomechanical basis of human movement. Philadelphia, PA: Lippincott, Williams, & Wilkens. Hansson, T., Roos, B., & Nachemson, A. (1981). The bone mineral content and ultimate compressive strength of lumbar vertebrae. Spine, 5, 46-55. Hattin, H. C., Pierrynowski, M. R., & Ball, K. A. (1989). Effect of load, cadence, and fatigue on tibio-femoral joint force during a half squat. Medicine & Science in Sports & Exercise, 21(5), 613-618. Hoffman, J ., Fry, A., Howard, R., Maresh, C., & Kraemer, W. (1991). Strength, speed, and endurance changes during the course of a division I basketball season. Journal of Strength and Conditioning Research, 5(4), 174-181. Isear, J. A., Jr., Erickson, J. C., & Worrell, T. W. (1997). EMG analysis of lower extremity muscle recruitment patterns during an unloaded squat. Medicine & Science in Sports & Exercise, 29(4), 532-539. Kauranen, K., Siira, P., & Vanharanta, H. (1999). Strength training for 1hr in humans: Effect on the motor performance of normal upper extremities. European Journal of Applied Physiology, 79, 383-390. Kraemer, W. J ., & Ratamess, N. A. (2005). Hormonal responses and adaptations to resistance exercise and training. Sports Medicine, 35(4), 339-361. 258 Kraemer, W. J., Ratamess, N. A., Fry, A. C., et al. (2000). Influence of resistance training volume and periodization on physiological and performance adaptations in collegiate women tennis players. The American Journal of Sports Medicine, 28(5), 626-633. Lander, J. E., Bates, B. T., & Devita, P. (1986). Biomechanics of the squat exercise using a modified center of mass bar. Medicine & Science in Sports & Exercise, 18(4), 469-478. Lander, J. E., Simonton, R. L., & Giacobbe, J. K. (1990). The effectiveness of weight- belts during the squat exercise. Medicine & Science in Sports & Exercise, 22(1), 117-126. Lehman, G. J. (2005). The influence of grip width and fore-ann pronation/supination on upper-body myoelectric activity during the bench press. Journal of Strength & Conditioning Research, 19(3), 587-591. Lindbeck, L., & Arborelius, U. P. (1991). Inertial effects from single body segments in dynamic analysis of lifting. Ergonomics, 34(4), 421-433. Linnamo, V., Hakkinen, K., & Komi, P.V. (1998). Neuromuscular fatigue and recovery in maximal compared to explosive strength loading. European Journal of Applied Physiology, 77, 176-181. McBride, J. M., Cormie, P., & Deane, R. (2006). Isometric squat force output and muscle activity in stable and unstable conditions. Journal of Strength & Conditioning Research, 20(4), 915-918. McCaw, S. T., & Friday, J. J. (1994). A comparison of muscle activity between a free weight and machine bench press. Journal of Strength & Conditioning Research, 8(4), 259-264. McGill. (2002). Low back disorders: Evidence based prevention and rehabilitation. Champaign, IL: Human Kinetics. McGuigan, M. R. M., & Wison, B. D. (1996). Biomechanical analysis of the deadlift. Journal of Strength & Conditioning Research, 10(4), 250-255. McLaughlin, T. M., Dillman, C. J., & Lardner, T. J. (1977). A kinematic model of performance in the parallel squat by champion powerlifers. Medicine & Science in Sports, 9(2), 128-133. McLaughlin, T. M., Lardner, T. J ., & Dillman, C. J. (1978). Kinetics of the parallel squat. Research Quarterly, 49(2), 175-189. 259 Moisio, K. C., Sumner, D. R., Shott, S., & Hurwitz, D. E. (2003). Normalization of joint moments during gait: A comparison of two techniques. Journal of Biomechanics, 36, 599-603. Nachemson, A., & Morris, J. M. (1964). In vivo measurements of intradiscal pressure. Journal of Bone and Joint Surgery, 4 6A(5), 1077-1092. NFHS (2008). NFHS participation figures. Retrieved July 15, 2008 from http://www.nflrs.org/custom/participationifigures/default.aspx. Nigg, B. M., MacIntosh, B. R., & Mester. J. (2000). Biomechanics of biology and movement. Champaign, IL: Human Kinetics. Ninos, J. C., Irrgang, J. J ., Burdett, R., & Weiss, J. R. (1997). Electromyographic analysis of the squat performed in self-selected lower extremity neutral rotation and 30 degrees of lower extremity tum-out from the self-selected neutral position. Journal of Orthopaedic & Sports Physical Therapy, 25(5), 307-315. Noble, B. J., Kraemer, W. J ., & Clark, M. (1982). The response of selected physiological variables and perceived exertion to high intensity weight training in highly trained and beginning weight trainers. NSCA Journal, 10-12. Pierce, K., Rozenek, R., & Stone, M. H. (1993). Effects of high volume weight training on lactate, heart rate, and perceived exertion. Journal of Strength & Conditioning Research, 7(4), 211-215. Perotto, A. O. (2005). Anatomical guide for the electromyographer. Springfield, IL: Charles C. Thomas. Raastad, T., & Hallen, J. (2000). Recovery of skeletal muscle contractility after high and moderate intensity strength exercise. European Journal of Applied Physiology, 82, 206-214. Rencher, A. C. (1995). Methods of multivariate analysis. New York, NY: Wiley. Robertson, D. G. E., Caldwell, G. E., Hamill, J., Karnen, G., & Whittlesey, S. N. (2004). Research methods in biomechanics. Champaign, IL: Human Kinetics. Russell, P. J ., & Phillips, S. J. (1989). A preliminary comparison of front and back squat exercises. Research Quarterly for Exercise & Sport, 60(3), 201-208. Saladin, K. S. (2001). Anatomy and physiology: The unity of form and function (2nd ed.) (2nd ed.). Boston, MA: McGraw Hill. Sands, W. A. (2000). Olympic preparation camps 2000 physical abilities testing. Technique, 20(10), 6-19. 260 Sands, W. A. (2004). Which muscles? USOC Olympic Coach Magazine Fall 2004. Retrieved March 10, 2006, from http://coaching.usolympicteam.com/archives. Sands, W. A., McNeal, J. R., Ochi, M. T., Urbanek, T.L., Jemni, M., & Stone, M. H. (2004). Comparison of the Wingate and Bosco anaerobic tests. Journal of Strength and Conditioning Research, 18(4), 810-815. Schonefelt, E. (1991). Immediate effect of weight training as compared to aerobic exercise on free throw shooting skills in collegiate basketball players. Perceptual Motor Skills, 73, 367-370. Shepard, G. (2004a). The BF S box squat. Retrieved March 26, 2005, from http://www.bigerfasterstronger.comALmagPrint.asp?id=3 l 9. Shepard, G. (2004b). Bigger faster stronger. Champaign, IL: Human Kinetics. Shepard, G. (2004c). Box squat warning. Retrieved March 26, 2005, from http://www.biggerfasterstronger.com/p ma§rint.asp?id=l33. Shepard, G. (2004d). Box squat? The first thing we do. Retrieved March 26, 2005, from http://www.biggerfasterstronger.com/p magPrint.asp?id=l45. Siff, M. C. (2003). Facts and fallicies of fitness. Denver, CO: Supertraining LLC. Signorile, J. F., Kwiatkowski, K., Caruso, J. F ., 8r. Robertson, B. (1995). Effect of foot position on the electromyographical activity of the superficial quadriceps muscles during the parallel squat and knee extension. Journal of Strength & Conditioning Research, 9(3), 182-187. Signorile, J. F ., Weber, B., R011, R, Caruso, J. F., Lowensteyn, I., & Perry, A. C. (1994). An electromyographical comparison of the squat and knee extension exercises. Journal of Strength & Conditioning Research, 8(3), 178-183. Signorile, J. F ., Zink, A. J ., & Szwed, S. P. (2002). A comparative electromyographical investigation of muscle utilization patterns using various hand positions during the lat pull-down. Journal of Strength & Conditioning Research, 16(4), 539-546. Simmons, L. (1998). Box squatting. Retrieved March 26, 2005, from http://www.deepsc_nlatter.com/strength/archives/ls9.htrn. Simmons, L. (2006). Louie Simmons' biography. Retrieved March 19, 2006, from www.westside-barbell.com. Sweet, T. W., Foster, C., McGuigan, M. R. M., & Brice, G. (2004). Quantitation of resistance training using the session rating of perceived exertion method. Journal of Strength & Conditioning Research, 18(4), 796-802. 261 Tritschler, K. (2000). Barrow & McGee ’s practical measurement and assessment (5th ed.). New York, NY: Lippincott, Williams, & Wilkins. Wilk, K. E., Escamilla, R. F., Fleisig, G. S., Barrentine, S. W., Andrews, J. R., & Boyd, M. L. (1996). A comparison of tibiofemoral joint forces and electromyographic activity during open and closed kinetic chain exercises. American Journal of Sports Medicine, 24(4), 518—527. Winter, D. A. (1990). Biomechanics and motor control of human movement. New York, NY: John Wiley & Sons, Inc. Winter, D. A. (1991). Biomechanics and motor control of human gait: Normal, elderly, and pathological. Waterloo, CA: Waterloo Press. Woolstenhulme, M., Bailey, 8., & Allsen, P. (2004). Vertical jump, anaerobic power, and shooting accuracy are not altered 6 hours after strength training in collegiate women basketball players. Journal of Strength & Conditioning Research, 18(3), 422-425. Wretenberg, P., Feng, Y., & Arborelius, U. P. (1996). High- and low-bar squatting techniques during weight-training. Medicine & Science in Sports & Exercise, 28(2), 218-224. Wretenberg, P., Feng, Y., Lindberg, F., & Arborelius, U. P. (1993). Joint moments of force and quadriceps muscle activity during squatting exercise. Scandinavian Journal of Medicine and Science in Sports, 3, 244-250. 262 ”1111111111 11131111 lilliljlllpllll