AN NYE TEGATEON OE THE ETEEGTE @F A TWELVE WEEK GWQETE‘SNTNG EEQGME GK THE ELECTRQWDTQGEAME @F ALBENO RATS Thests {too {Tm Dogma of M. A. MICHIGAN STATE UNIVERSITY Kenneth James Ackerman 1959 WLIM my... '0 o. . . _ , u..- MSU LIBRARIES m » RETURNING MATERIALS: Place in book drop to remove this checkout from your record. FINES wiII be charged if book is returned after the date stamped below. Z 86 I I ' A P' AA I-A' HQSTRUCTMD~~ COLE-CU 31. * NIVER ‘ ‘ C M. . ‘r fc. LA ‘ZzéiflqTEi AN INVESTIGATION OF THE EFFECTS OF A TWELVE WEEK CONDITIONING PROGRAM ON THE ELECTROCARDIOGRAMS OF ALBINO RATS by KENNETH JAMES ACKERMAN AN ABSTRACT Submitted to the College of Education of Michigan State- University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF ARTS Department of Health, Physical Education, and Recreation Year 1959 Approved 1.0 ‘ n." r- v ' "'!"'\' bUREfiV" kn” LDk,\l'\\ilX-!j\l.{\L RESEARCi-i w: ‘.. , . rm,” . . Cu‘LLW. . CF LL'U‘VATION IMCMGNJSMH;UJIHbHY EAST LANSING, MICHIGAN 2 KENNETH JAMES ACKERMAN ABSTRACT Statement of the Problem The problem of this study was to determine the effect of prolonged physical conditioning on the electrocardiograms of albino rats. Methodology Forty-eight albino, male, litter-mate rats of the Sprague-Dawley strain were divided into three eXperimental groups: Groups A and B were swum twice daily for twelve weeks, and Group C remained sedentary. Groups A and C were fed a stock diet, and Group B was fed the same stock food with 30 per cent of their daily caloric in-take coming from powdered whole milk. Electrocardiogrgms were taken before and after the conditioning program. The output from a Twin-Viso Sanborn direct writer electrocardiograph was fed into an Oscillo- scope to record the ECG's. Records were taken from the Oscilloscope by means of a polaroid camera mounted on the scope face. At the conclusion of the twelve week conditioning period, the animals were subjected to an all-out swimming performance test. They were then sacrificed and dissected Body organ weights were recorded. Records from the two recording instruments were com- pared by means of the Pearson Product-Moment coefficient of correlation and the "t" test. 3 KENNETH JAMES ACKERMAN ABSTRACT The simple analysis of variance technique was employed in analyzing the "pre-conditioning" and"post—conditioning" data. The Student "t" was used to compare Groups A and C. Correlations were computed on the ECG data and heart weight, heart rate, and all-out swim time. ConcluSionS l. The direct writer is not adequate for recording the electrocardiograms of rats. The use of the Oscilloscope gives a more accurate reproduction of the rat ECG. 2. The heart rate of the rat decreases with age and is slower in the rats receiving exercise. 3. P-wave and T-wave magnitudes of rats decrease with age. Conditioning tends to retard the decrease. 4. The QRS magnitude is increased or maintained by conditioning; while a sedentary life produces a reduction in this amplitude. 5. The direction of the electrical force in the rat's heart in respect to the P and T-waves changes with age. Conditioning has no effect on this. 6. The P-R and R—T intervals decrease with age. Conditioning has no effect on the P-R interval, but tends to retard the decrease in the R-T interval. 7. The QRS interval lengthens with conditioning, and decreases with a sedentary life. AN INVESTIGATION OF THE EFFECTS OF A TWELVE WEEK CONDITIONING PROGRAM ON THE ELECTROCARDIOGRAMS OF ALBINO RATS by KENNETH JAMES ACKERMAN A THESIS Submitted to the College of Education of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF ARTS Department of Health, Physical Education, and Recreation 1959 ACKNOWLEDGMENTS The author wishes to acknowledge Dr. Henry J. Montoye, Professor, of the Department of Health, Physical Education, and Recreation, for his assistance in designing this experi- ment and for his interest and guidance in the preparation of this thesis. Special thanks is extended to William Holscher, who shared the responsibility of caring for and exercising the animals; Richard Schmal for his assistance in preparing the testing apparatus; and to my wife for her constant encour- agement and assistance throughout the experimental period. TABLE OF CONTENTS CHAPTER I. INTRODUCTION. . . . . . . . . . The Problem . . . . . Importance of the problem Statement of the problem. . . . Definition of Terms . . Limitations of the Study. . II. REVIEW OF THE LITERATURE. The Swimming of Small Animals . . . The ECG of Rats. . . Effects of Exercise on the ECG. Effect of Sodium Pentobarbital on the ECG Use of Direct Writer in Small Animal ECG Work. . III. DESIGN OF THE EXPERIMENT. The Sample . . . . . . . The Methods . . . . . . . . . Type and amount of exercise. . Procedure for taking ECG's Measurements. . . . Statistical Analysis . . . . . . PAGE h.) NUT 43th) 10 ll l2 l2 13 14 l6 18 2O CHAPTER IV. PRESENTATION AND DISCUSSION OF DATA. Results: Correlation Of Test Instruments. Results: Effects of Conditioning on ECG's Analysis of Variance . . . "T" test. . . . . . . . . . Intercorrelations. . . . . . Discussion Direction of electrical force. Intervals and heart rate . Intercorrelations. . . V. SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS. Summary . . . . Conclusions. . . . Recommendations . . . . . . . BIBLIOGRAPHY . . . . . . . . . APPENDIX. . . . . . APPENDIX A--Conversion Formulas. . . . . APPENDIX B--Swim Times, Heart Rates, and Heart Weights. iv PAGE 22 22 2A EA 28 28 28 32 3A 37 38 38 40 Al A3 46 A? 48 TABLE II. III. IV. VI. VII. VIII. LIST OF TABLES PAGE Number, rank, and markings of the animals. . 15 Results of the correlation between the direct writer and Oscilloscope . . . . 23 Electrocardiogram measurements: pre- condition means, standard deviations, and F-ratios . . . . .t . . . . . 25 Electrocardiogram measurements: post- condition means, standard deviations, and F-ratios . . . . . . . . . . 26 Electrocardiogram measurements: means, standard deviations, and F-ratios of the differences; before and after conditioning 27 Electrocardiogram measurements: comparison of "individual differences" between groups A and C. . . . . . . . . . 29 Correlations between electrocardiogram meas- urements and heart weight, heart rate, and all-out swim times . . . . . . . 30 Comparison of mean T-P segments and mean total cycle lengths . . . . . . . . 37 FIGURE UTE—“DOM Technique for preparing the animals for LIST OF FIGURES ECG recording. Comparison of ECG magnitudes. Comparison Comparison Comparison of ECG directions in degrees of ECG intervals of heart rates. PAGE 17 31 33 35 36 CHAPTER I INTRODUCTION The electrocardiogram has become one of the most valuable instruments available for the detection of the various abnormal heart conditions. Since Einthoven, in 1903, introduced the string galvanometer for recording electrocardiograms, ECG's have been routinely taken in heart cases. In the past two decades electrocardiographic evaluation of exercise has become increasingly popular and seems to have considerable value.1 I. THE PROBLEM Importance of the problem. It has been shown that the electrocardiogram of athletes, when in training, show definite changes which fall outside the normal limits.2 lEarnest Simonson, M.D., and Ancel Keys, Ph.D., "An Electrocardiographic Exercise Test: Changes in the Scalar EGG and in the Mean Spatial QRS and T Vectors in Two Types of Exercise: Effects of Absolute and Relative Body Weight and Comment on Normal Standards," American Heart Journal, 52:83, July, 1956. 2George L. Beckner, M.D., and Travis Winsor, M.D., '"Cardiovascular Adaptations to Prolonged Physical Effort," Circulation, 9:844, June, 195“. The recognition of these as physiologic changes in the heart which result from prolonged, intensive conditioning is important because the resulting changes are similar to those which are associated with disease.3 Statement of the problem. The purpose of this was to determine what effects a prolonged conditioning period has on the electrocardiograms of albino rats. II. DEFINITION OF THE TERMS The terms used in connection with electrocardiograms are defined in Katz's book on standardized electrocardio- graphic terminology.“ Sedentary group. That group of animals which were confined to their cages with no physical activity for the entire experimental period. III. LIMITATIONS OF THE STUDY 1. The problem of transfering the results of an animal study to humans is always a limitation. 2. The use of vernier caliphers for measuring the amplitudes and intervals was not precise enough for the small deflections and intervals which were encountered. 3Ibid., p. 835. 4Louis Nelson Katz, Electrocardiography (Philadelphia: Lea and Febiger, 1946). 3 3. Intensity of the conditioning program in a study of this nature is always a problem. It would be better to use a training program where work output could be measured quantitatively. CHAPTER II REVIEW OF THE LITERATURE I The swimming of small animals. Wilbur forced guinea pigs to swim to exhaustion with weights attached, varying from 60 to 900 grams (1-10% of body weight), at water temperature of 380 C. He found that if the animals were forced to swim in a group, 70% showed a 50% decrease in swimming time. From these results he suggests that, for the best results, small mammals be swum alone. In studying the effect of liver supplement to the diet of rats upon their swimming capacity, Ershoff2 found that all rats, regardless of diet swam for an arbitrary limit of 120 minutes in water at 360 C. However, when the same animals were swum at 200 C, those without the liver supplement swam 13 minutes as compared to 120 minutes for those animals with the liver supplement. He also found that the animals rarely stay submerged more than 5 to 10 1Charles G. Wilbur, "Some Factors Which are Corre- lated with Swimming Capacity in Guinea Pigs," Journal of Applied Physiology, 16: 199-203, March, 1959. 2Benjamin H. Ershoff, "Beneficial Effect of Liver Feeding on Swimming Capacity of Rats in Cold Water," Society for Experimental Biology and Medicine, 77: A88-A9l, 1951. seconds and that animals remaining below the surface for a period longer than 15 seconds drowned in most cases. The Egg of E§§§~ In studying the electrocardiograms of albino rats in chronic thiamine deficiency, Hundley, Ashburn, and Sebrell3 used a string galvanometer coupled with a Sanborn "Cardioscope" amplifier in the circuit. The instrument was standardized so lmV produced 2cm. of deflection. The camera speed was set at 75mm. per second. They took ECG's from Leads I, II, and III with the animals held in their normal position. No anesthesia was used. The ECG's were taken at weekly or bi-weekly intervals. From this experiment the following "normals" for rat ECG's are reported: 1. Lead I shows a low deflection. 2. The P-R interval ranges from 0.035 second to 0.05 second and increases with age. 3. The QRS interval ranges from 0.006 second to 0.013 second and increases with age. A. The Q-T ranges from 0.05 seconds to 0.09 second and varies inversely with heart rate. 5. It is common to find the P-wave coming before the T-wave returned to the isoelectric line. 3James M. Hundley, L. L. Ashburn, and W. H. Sebrell, '"The Electrocardiogram in Chronic Thiamine Deficiency in Rats," American Journal of Physiology, 1AA: 404-414, August, I935. 4 observed the ECG's in normal Waller and Charipper Thyriodectomized and Thiourea treated rats. They used 50 hooded albino rats; 24 males and 26 females. The animals were given 30 mg. of nembutal/Kg of body weight and the electrocardiograms were recorded by a commercial string galvanometer electrocardiograph with an electronic amplifier. Using Lead II, the following means were reported: 1. P—R interval - 0.047 Sec. i 0.002 (.038-.053) 2. Height of R2 waves - 0.463 mV i 0.097 (.300 -.750) 3. Height of T2 waves - 0.106 mV : 0.029 (.050 -.225) They also noted low deflections in Lead I, and well formed S-waves in the majority of cases in Leads II and III. Ensor,5 studied the ECG's of rats on a vitamin E deficiency for one year. He used 20 animals and recorded the electrocardiograms with a Sanborn Electrocardiograph with a camera speed set at 5cm./Second. The recorder was set so lmV produced lcm. deflection. No anesthesia was used and the recordings were taken at 4 week intervals for 24 weeks, then at 8 week intervals. He found that vitamin E deficiency has no effect on the ECG's and reported the following measurements: “Robert K. Waller and Harry A. Charipper, "Electro- cardiographic Observations in Normal Thyroidectomized and Thiourea Treated Rats," American Journal of the Medical Sciences, 210: 443- A52, OchEer, 5Charles R. Ensor, "The Electrocardiogram of Rats on Vitamin E Deficiency," American Journal of Physiology, 147: 477- 479, November, 194 6. l. P-R interval--4 weeks (0.04 sec.)--l year (0.45 sec.) 2. QRS interval--4 weeks (0.01 sec.)--l year (0.015 sec.) 3. T-wave--Lead I--0.02 sec. to 0.05 sec. Lead II and III--0.06 sec. to 0.09 sec. The P-wave was again observed occurring before the T-wave reached the isoelectric line. Berg6 studied the ECG's of 144 rats as they advanced in age. He found no change in the P-wave; lengthened P-R and QRS intervals; left axis deviation in 6OO/o of the rats 800 days old; and a slowing heart rate. Effects of exercise on the Egg. There is a multitude of literature on the effects of exercise on the electro- cardiogram. However, a large portion of it is concerned with the immediate effects that exercise produces on the ECG. This review is concerned only with that portion connected with prolonged physical conditioning. Hoogerwerf,7 in 1928, studied the ECG's of 260 Olympic Athletes using a string galvanometer to record the three 6BenJamin Berg, "The Electrocardiogram in Aging Rats,“ Journal of Gerontology, 10: 420-423, October, 1953. 7S. Hoogerwerf, Ergebnesse der sportaztlichen Unter- suchun en bei den IX OIympiséhen SEIelen, pp. ITS-38, Berlin, I929;'“EIeEFFOEEFdTOgrahischeUfitersuchungen der Amsterdamer Olympiade," Arbeitsphysiologie, 2:61, 1929, cited by T. K. Cureton, PhysICaI Fitness 0? Champion Athletes (Urbana: University 0? IIIinoIs PreSS, I951), p. THO. standard leads. He found that athletes, in the resting state, have a higher T-wave than sedentary individuals, the S-wave is eliminated, the RS-T segment is raised, and generally the P-wave is small. Tung, at El-’8 in 1934, conducted a study of 46 healthy Chinese ricksha pullers who had been at that job for a minimum of one year prior to the study. They took ECG's from Leads I, II, and III with the subjects in the recumbent position. The results showed that the electrical axis of the QRS complex was normal in 40 of the subjects and in 16 cases a tall T-wave deflection was observed in one or more leads. Using 48 athletes, consisting of 4 wrestlers, 7 gymnasts, 9 swimmers, 6 basketball players, and 22 trackmen, Tuttle and Korns,9 in 1941, observed the effects of conditioning for a season on the electrocardiograms of athletes. They took ECG's at the beginning of the season and again near the conclusion. The results showed no qualitative changes from the beginning to the end of the season in 43 of the subjects. In one case the changes 8C. L. Tung, et al.,'"The Hearts of Ricksha Pullers: A Studycf the EffecE—oT—Chronic Exertion on the Cardio- vascular System," American Heart Journal, 10:79-100, October, 1934. 9W. W. Tuttle and Horace M. Korns, "Electrocardio- graphic Observations on Athletes Before and After a Season of Physical Training," American Heart Journal, 21:104-107, January, 1941. that occurred were insignificant, 3 subjects showed an inverted T-wave in Lead III after training, and in one case the P-wave, which was inverted before the season, became upright with training. In 1951, Foerchlo compared the electrocardiograms of 20 "top notch" athletes with 20 non-athletes who had never played high school or college athletics. He found that athletes have statistically significant longer Q-T and P-R intervals and greater T-wave amplitudes than non- athletes. The non-athletes showed a longer QRS interval. 11 in 1958, conducted a study of the Rasch, 32 31., electrocardiograms of United States Olympic Free Style wrestlers. There were 74 subjects, ranging from 16 to 47 years old. The ECG's were recorded at the weigh-in time. They concluded that the ECG's of highly trained wrestlers were not different than those of healthy non-wrestlers of the same age. The wrestlers ECG's were compared with pub- lished norms. The authors found no evidence that training causes pathologic changes in the normal heart. 0Richard L. Foerch, "A Comparison of Electro- cardiographic Measurements of Athletes and Non-Athletes at Michigan State College" (unpublished Master's thesis, Michigan State College, 1951). 11 Philip J. Rasch, 22 al., "An Electrocardiographic Study of United States OlympTE Free Style Wrestlers," Research Quarterly, 29:46-53, March, 1958. IO EEEEEE 93 sodium pentobarbital on the ECG. Blouinl2 studied the effects of position and anesthesia on the ECG of the normal dog. He anesthetized 20 "normal" mongrel dogs with 30mg./Kg. of body weight of sodium pentobarbital (Nembutal) and used six dogs which were trained to be quiet as controls. He recorded tracings of the trained dogs while they were unanesthesized and anesthesized. He found that nembutal supressed the Q-waves; as 65% of those dogs which were unanesthetized had Q-waves, but only 12% of those which were anesthetized had Q-waves, Nembutal had little and unpredictable effects on the P and T-waves and when given in large doses (30mg/kg) causes tachycardia, but in lighter doses (20mg/kg) produced normal heart rates. In regard to heart rate and intervals, he found little difference between durations of the P-R, QRS, and Q-T intervals despite the variation in heart rates. He concluded that there was no predictable relation- ship or variation on the ECG's of the trained dogs, either anesthetized or unanesthetized. l2Leonard Thomas Blouin, "Effects of Position and Anesthesia upon the Electrocardiogram 0f the Normal Dog" (unpublished Master's thesis, Michigan State University, 1956). 11 Use of direct writer in small animal ECG work. Rappaport and Rappaport13 report that the commercial electrocardiograph is designed for human work and is not suitable for small animal work. (A more exact tech- nique is needed for the work carried on with small animals due to their increased heart rate. 13Maurice B. Rappaport and Irving Rappaport, '"Electrocardiographic Considerations in Small Animal Investigations," American Heart Journal, 26:677, November, 1943. CHAPTER III DESIGN OF THE EXPERIMENT This experiment was designed to investigate the effects that a prolonged conditioning program produces on the electrocardiograms of male albino rats. I. THE SAMPLE Forty-eight albino, weanling, male, litter-mate rats of the Sprague-Dawley strain were used in this experiment. Each litter was composed of three animals. The animals were kept confined in cages 5" x 5" x 12" in a thermostatic controlled room with no direct sun light from January to June, 1959. From January to March all 1 animals were kept confined and fed a stock diet. 1Ingredients of the stock diet in percentages: 46.1 ground corn 0.5 Track mineral salt 20.0 so bean Oil meal 3.0 corn oil (44% protein) 10.0 fish meal 0.1 Merck B Vitamin 5.0 17% dehydrated alfalfa 0.05 Vit. A and D mix meal 10.0 dried skim milk .25 Pfizers 9 + Vit. B12 Sup. 5.0 sucrose sugar Tocopherol Acetate 20g/10Q# 13 This time was used to allow the animals to pass through the stage of rapid growth. The animals were divided into three experimental groups (A, B, and C) by weighing each animal in the litter and ranking them 1, 2, and 3, according to their respective litter. They were then placed in the three groups by alternating the ranked weights. The animals were numbered and placed in numbered cages. The cages were arranged in a rack so there were two animals from each group in each row. Numbers 1-16 were given Group A; Group B, 17-32; and Group C, 33-48. Group A was placed on the stock diet plus exercise; Group B was given the stock diet, with 30 per cent of their daily calorie intake coming from powdered whole milk, and exercise;2 and Group C received the stock diet and served as controls, remaining sedentary throughout the experiment. The animals were marked for identification by a com- bination of ear punches and dye markings. This system was necessary because the animals were shipped in two lots of eight litters, with duplicate ear punches. All animals from one lot were given a dye mark on the right leg in order to identify the sixteen litters. The animals were 2Group B was given the 30 per cent milk diet in connection with another aspect of this study designed to study the effects of exercise and milk on performance and organ growth. 14 then marked for group identification: Group A was marked with two spots on the back, Group B with one spot on the back, and Group C had no back mark. The animals‘ cages were rotated one spot daily to compensate for light and temperature deviations which might have existed. Table I gives a complete resume of how the animals were ranked, numbered, and marked. II. THE METHODS Type and amount 2E exercise. Each animal in the two exercise groups received an equal amount of conditioning. They swam in their respective groups twice daily, Monday through Friday and once on Saturday, for twelve weeks. Two 24" x 24" x 18" metal tubs filled with 13" to 14" of water were used for the swimming. One week was spent swimming the animals for short periods without attached weights. Experimentation with water temperature was also carried on during this period. One animal drowned at 400 C. The second and third weeks were spent swimming the animals for periods of 10 minutes with 4% of their body weight attached by means of a harness. Several animals were unable to swim the full 10 minutes and four animals drowned. Two of these animals drowned in the tank set at 400 C. and two in the tank at 370 c. 15 .pzoEHHoaxo on» no omHSOO 0:» CH BOHQN Til o o: HHHm m s H on HHHm N Nm N on HHHm H 6H 0 no» HmHm H s H nos HmHm m Hm N no» HmHm N mH 6 on m N as H on m H oom N on m m osH o noNH mm m m: H mm» mm m mm m mom mm H MH 0 on Nm H .H H on Nm m mN N on Nm N NH 0 mos Nm N s H was Nm H N N nos Nm m oHH o on Hm m N: H on Hm N oN N on Hm H ooH 0 mos Hm H H: H no» Hm m mN N was Hm N N o o: mH N o: H on mH H HN N on mH m m o no» mH m mm H mm» mH m mm m mom mH H s 0 on NH H mm H on NH m eNN N or NH N m o no» NH N am H no» NH H HN N no» NH m em 6 on HH m mom H on HH N 0N N o: HH H s o no» Hm H mm H no» Hm m NH N was Hm N em 6 o: OH H N :m H on 0H m H mH N on 0H m m N o as» 0Hom m mm H was 0Hom N SH N no» 0Hom H H Has: ooHsom gonna soupHH .oz ans: oeHsrm gonna soreHH .oz Haas oeHsnm gonna noeeHH .oz Howm mOH Ham CH Howm wOH Ham CH xomm mOH Hmm CH seem scam seem oanoz panoz onNHoz o azoac m adoac < adoau mHesza awe mo oszmez Hza .Hzam .mmmzpz H mamde 16 Starting with the fourth week of the experiment, the rats were swum without the attached weights. The length of the daily training period was increased to 30 minutes (twice daily) and increased five minutes weekly until one hour was attained. When this was reached, it was held constant through the remainder of the experiment. Water temperature was standardized at 360 C to 370 C. Procedure for taking the electrocardiograms. Two records were taken on each animal; one before the training period and one near the conclusion. Leads I, II, and III were recorded. It required two days to complete the ECG's on each test session. The animals were injected with a three per cent solution of Sodium Pentobarbital (Nembutal) in a dosage of approximately.l6cc/100 grams of body weight. (The amount of nembutal needed varied with the animal.) When the animal became quiet to the extent that he could not hold his head erect, he was placed upon his back on a flat board and fastened in place by stretching rubber bands from each extremity to hook screws on the board. Needle electrodes were inserted under the skin of each extremity (Figure 1). Two instruments were used to record the ECG‘s on the first testing. A Twin-Viso Sanborn direct writing recorder (model-60-1300) was used for the initial pickup. An Oscilloscope (model-130A) with a polaroid camera mounted Figure 1. Technique for preparing animals for ECG's recording. 17 18 on the screen was hooked into the recorder and pictures were taken of the waves as they passed on the screen. The recorder was set so lmV produced 15mm. of deflection and was operated at a speed of lOOmm./Sec. The Oscillo- scope was calibrated so lmV produced 28mm. of deflection the first day and 29 mm. the second day, and was operated with a sweep time of 50 milliseconds/Cm. The use of the Oscilloscope and polaroid camera adds to the expense of conducting an animal experiment of this nature. However, upon comparing previous pictures with the corresponding direct writer electrocardiograph records, it was felt that the pictures gave the more accurate reproduction of the rat ECG. Differences were especially noted in the R and S-wave deflections. The statistical analysis used to determine the relationship between these instruments is discussed in the Statistical Analysis section of this chapter. The post-condition ECG's were recorded in the same manner with this exception: The recorder was used for just the heart rates of the animals. Calibrations used on the Oscilloscope were lmV = 28 mm. deflection and lmV = 27 mm. of deflection. Measurements. The following amplitudes were measured with vernier caliphers in Leads I and III: P-wave, R-wave, S-wave, and T-wave. The algebraic sum of the R and S-waves constituted the QRS complex since no Q-waves were observed. 19 The intervals were measured with the same instrument and included the following: P-R interval, QRS interval, and R-T interval. The intervals were measured from Lead II on the first test and Lead III on the second. All raw measures were recorded in millimeters; the amplitudes were converted to millivolts and the intervals to seconds (Appendix A). Heart rates were computed from the Sanborn electro- cardiograph by counting the number of beats in three dif- ferent one second intervals, adding them, and multiplying the sum by twenty. All amplitudes were measured from the isoelectric line to the peak of the deflection. The intervals were measured by the following procedure: P-R interval, from the point where the P-wave started to the beginning of the R-wave; QRS interval, since no 0-waves were found, the QRS interval was represented by the space from the start of the R-wave to the point where the S-wave intersected the isoelectric line; R-T interval, from the beginning of the R-wave to the point where the T-wave returned to the base line or to the next P-wave. All-out swim times were obtained by swimming each animal individually in a galvanized container filled with twenty inches of water. Six per cent of the animal's body weight was attached for this test. Each animal was allowed to swim until he could no longer regain the surface after being submerged for approximately 15 seconds. 20 The animals were sacrificed,diasected, and body organ weights were recorded. III. STATISTICAL ANALYSIS Using the pre-condition results, Pearson Product- Moment coefficients of correlation were computed for the data collected on the Oscilloscope and those from the Sanborn direct writer in an effort to determine the degree of relationship between the instruments. The "t" test was used to compare the means from these records. Vectors for the P-wave, QRS complex, and T-wave were computed from the amplitudes of the "pre-condition," and '"post-conditiod'records. Tables designed for this analyses by Jackson and Winsorl were used. Oscilloscope records were used for all final statistical analysis. F-ratios were computed on the "pre-condition"vectors and intervals, "post-condition" vectors and intervals, and the "individual differences" obtained from pre-condition to post-condition. The Student "t" was used to compare the means of the "individual differences" of Groups A and C, which were the stock diet animals. 1Charles E. Jackson and Travis Winsor, "Aids for Determining Magnitude and Direction of Electrical Axes of the ECG," Circulation, 1:975-981, April, 1950. 21 Correlations were calculated on the post-condition ECG's and heart weight, heart rate after conditioning, and all-out swim time (see Appendix B for these raw meas- ures). CHAPTER IV PRESENTATION AND DISCUSSION OF DATA This study was undertaken to determine the effects of a prolonged conditioning period on the ECG's of albino rats. Forty-eight animals were divided into three groups. Two groups were subjected to a swimming conditioning program and one group remained sedentary. Electrocardio- grams were taken before and after a twelve week condi- tioning period. I. RESULTS: CORRELATION OF TEST INSTRUMENTS A Summary of the results is presented in Table II. Statistically significant "t's" at the 0.01 level were found in the R—wave (I), S-wave (I), and the R-wave (III). Differences in the S-wave (III), T-wave (III), and R-T interval were significant at the 0.001 level. In all instances except the R-T interval, the larger mean was obtained from the Oscilloscope records. The author feels the reversal noted in the R-T interval was caused by the failure of the T-wave on the direct writer records to return to the base line before the following heart beat started. The records from the Oscilloscope 3a .wwm .Q .xmwcoaa o sou .opH .HHNm one smennmo H.0cH .mcom can HoHHz snow ” How 2. 302V mOHumHuwpm HNOHwOHoc Hum HNEOZoz QCHSG mo m oHnt EOHM Comm» mHo>0H oocnoHMHc HmH .Ho>0H Hoo. on» no pdNOHchmHm** .Ho>0H Ho. 0:» um HQNOHchme* It: HHIIIIIIILVIIIIIII :N. **ms.s ms soo.lri mmo.lln. NHL. IImHo. omo. AHHVHMM mo.- Ho. we moo. mHo. we Noo. mHo. HHHmea mm. SN.H we smo. omo. ms moo. mso. AHHVm-N 5mm? Hm. *smH.m we mac. oom. we see. ANN. HHHHVo>os-e so. **ms.m ms moH. omo. we moo. 0N0. HHHHVo>oz-m em. *mm.N m: mmH. HNN. we moH. cam. HHHHVo>a3-m so. on. we mmo. NSH. ms Hmo. mmH. HHHHVo>o3-N mo. on. we oso. Hmo. we nee. meo. AHV o>e3-H mm. *Nm.N m: coo. mmo. we omo. mmo. HHS osez-m ms. *oH.m we mac. me. we Hao. mmH. HHV o>o3-m oo. mm. NH amo. oeo. NH oNo. see. HHS oses-a H p z OQOommewomo E z .mVMpooom z n0©%%fiwae< HH MHmoH Hoo. one no osooHochHm* oo.o mH soo. ooo. HH ooo. ooo. HH moo. moo. e-m *oo.m mH Noo. oNo. HH Noo. mHo. HH Noo. oHo. mmo so.N mH moo. meo. HH ooo. Nmo. HH Hoo. eso. m-N A.moomv mHo>H0psH mm. mH m.HH H.os SH m.NH H.ss HH o.oH s.ms o>os-e on. mH o.sN m.mo NH m.sN m.mo HH H.oN m.om onaaoo mmo oo. mH H.SH o.No NH H.oN m.so HH m.oN H.No o>oz-a Amoopmoov COHpooaHo EN.N mH HH. om. SH HH. as. HH mo. ms. o>o3-9 Ha. mH mH. Nm. sH oH. Hm. HH HH. ms. onosoo mmo NH.N mH o Sm. sH so. mm. HH oo. Nm. o>o3-N z .H.m z z .H.m z z .H.m z oHrem-a I mooercmez o adopw m QSOHw 4 ozone mOHBmm Qm90ch wo. mH m.om s.mw HH m.mm w.wm HH H.om m.mm o>o3ue mH.N mH H.oN m.Ns eH N.mH H.mo HH H.mH o.No onosoo mmo Hm. mH s.mm m.om :H m.mm H.3m HH m.mm m.:m o>o3nm Ammonwoov QOHpooHHQ oo.o mH mo. om. :H mo. om. HH mo. mm. 0>Nzne om.o mH HH. ma. NH mH. Hm. HH mH. oz. UHOHQEoo mmd oo.o mH mo. mm. :H so. om. HH mo. mm. o>m3am z .Q.m s z .o.m z z Him 2 oHmeum o asopo m esopo < osopo mooSHchm: E mOHEmQ demz<9m NWZ¢mE ZOHBHDZOOIBmom >H mflmoH Hoo. one no ossoHoHsNHm* mm. mH HHo. oHo.u :H moo. soo.n HH HHo. Hoo.: Bum *mm.wH mH moo. moo.- :H moo. Hoo. HH moo. moo. mmd Hm. mH moo. moo.u :H woo. moo.n HH woo. Hoo.: mum A.moomv mHN>HOHCH mm. mH m.mm w.~ a :H m.mm m.an HH 5.3m o.oHn o>o3ue om.N mH s.mm m.mN- sH N.mN m.m - HH m.mN H.m onosoo mmo mm. mH m.:m m.H u :H m.:m m.oHu HH m.mm m.su o>m3nm Amoopwoov COHpooaHo mH.H mH NH. om.n :H oH. HH.: HH HH. HH.- m>w3ue mm.m mH MH. mo.u :H MH. Ho.n HH HH. mo.u onano mmd om.H mH mo. mo.- :H mo. mo.u HH mo. No.- o>o31m z .Q.m 2 7H .Q.m 2 HA .Q.m z oHpom-m cospHcmaz o adono m adoao < adoao I H GZHZOHBHQZOO mmem< Qz< mmommm «mmozmmmmmHQ Mme mo mOHBmQ Qm mqm<8 . 28 This is substantiated by the significance found in the '"individual differences" of the QRS interval. jig: test. The'"t" test, used to compare the means of the"individual differences" of Groups A and 0, revealed significance in the QRS interval (.001 level) and in the direction of the force of the QRS complex (.05 level). These data are presented in Table VI. The direction of the electrical force changed only slightly with condi- tioning; while the sedentary animals showed a sizable change. Intercorrelations. A summary of the correlations is reported in Table VII. The "r's" were too low to account for any appreciable amount of variance. III. DISCUSSION: EFFECTS OF CONDITIONING From Figure 2 it can be seen that the magnitude of the electrical force decreased in the P-wave and T-wave in all three groups. Perhaps this drop is due to the aging of the animals. It should be noted that a more marked drop occurred in the sedentary animals; possibly indicating that conditioning retards the aging process. The results show that the QRS complex magnitude is maintained or slightly increased with conditioning; while the sedentary life of the animals in Group C experienced a sharp drop in this magnitude. Again, conditioning may inhibit aging effects on the heart. ELECTROCARDIOGRAM MEASUREMENTS: OF "DIFFERENCES" BETWEEN GROUPS A AND C TABLE VI COMPARISON 29. Magnitude Group A Group 0 Mt" M N M N P-wave —.02 ll -.08 15 1.85 QRS complex -.02 ll -.09 15 2.02 T-wave -.14 ll -.20 15 1.34 Direction (degrees) P-wave -7.5 11 -l-3 15 .57 QRS complex 5.1 11 -25.8 15 2.13* T-wave ‘-l0.0 11 -7.7 15 .18 Intervals (secs.) P-R -.001 11 -.003 15 .97 QRS .003 11 -.003 15 5.11** R-T -.004 11 -.010 15 1.15 r _— *Significant at .05 level.1 **Significant at .001 level. 1Same as reference in Table II. CORRELATIONS BETWEEN THE ELECTROCARDIOGRAM MEASURES AND HEART WEIGHT, HEART RATE, TABLE VII AND ALL-OUT SWIM TIMES ~— 3O ECG Measure Heart Weight Heart Rate Swim Time Magnitude P-wave .09 .02 .ll QRS complex .08 -.13 .ll T-wave -.03 .ll -.05 Direction (goggees) P-wave -.20 .21 -.08 QRS complex .25 -.09 .15 T-wave -.30 -.04 .Ol Intervals _(sec.) P-R .08 .02 .08 QRS .06 -.16 .23 R-T .29 .03 .02 Comparison of ECG Magnitudes. Figure 2. 32 A previous study on the aging effect on rat ECG's revealed no change in the P-wave.l In human ECG work, two points of view are expressed: Conditioning produces a smaller P-wave and a higher T-wave;2 or no changes.3 Direction of electrical force. Changes in the direction of the electrical force are illustrated in Figure 3. It appears that the change found in the P-wave is due to training since the sedentary animals experienced only a very slight change as opposed to the larger change in the conditioned animals. The sedentary animals experienced a sharp change in the QRS complex; while conditioning produced only slight variations. The difference between Group A and Group C was significant. T-wave changes were nearly the same in all animals. Apparently conditioning has no effect on this portion of the rat ECG; the major factor causing the changes being age. 1Benjamin Berg,‘"The Electrocardiogram in Aging Rats," Journal of Gernotology, 10:420-423, October, 1953. 28. Hoogerwerf, Ergebnesse der spotaztlichen‘Unter- suchun en bei den IX 01 piscfien SpieIen,pp. 118-38, Bérlin, I9293'HEIeEEFoEEFdI5gra ische Untersuchungen der Amsterdamer Olympiade," Arbeitsphysiologie, 2:61, 1929, cited by T. K. Cureton, PhysicaI Fitness of Champion Athletes (Urbana: University 0? IIIinoIs PreSS, I95I), p. I30. 3W. W. Tuttle and Horace M. Korns, "Electrocardio- graphic Observations on Athletes Before and After a Season of Physical Training," American Heart Journal, 21:104-107, January, 1941. Comparison of ECG Directions in Degrees Figure 3. 34 Berg}4 reported left axis deviation in aging rats. Deviations obtained in this study were to the right. Tung,5 gt gl., reported that strenuous physical activity produced no change in the electrical axis of the QRS complex of humans. Intervals and heart rate. Figures 4 and 5 present graphic illustrations of these results. The P-R and R-T intervals decreased in all three groups. The QRS interval decreased in the sedentary animals, but increased in the conditioned animals. The differences in the QRS interval were significant. Heart rates decreased in all three groups during the experiment. The conditioned groups showed slower heart rates than the sedentary animals. Berg6 also noticed slower heart rates in rats as they advanced in age. Other studies on rats have indicated that the inter- vals of the ECG increase with age.7 “Berg, 92. cit., pp. 420-423. 5C. L. Tung, et 21" "The Hearts of Ricksha Pullers: A Study of the EffeEEs of Chronic Exertion on the Cardio- vascular System," American Heart Journal, 10:79-100, October, 1934. 6Berg, op. cit., pp. 420-423. 7James M. Hundley, L. L. Ashburn, and W. H. Sebrell, '"The Electrocardiogram in Chronic Thiamine Deficiency in Rats," American Journal of Ph siology, 144:404-414, August, 1945; Charles R. Ensor, "The ec rocardiogram of Rats on Vitamin E Deficiency," American Journal of Physiology, 147: 477-479, November, 1946? Berg, gp.)gl§.,_5p. 420-4237 5 3 Comparison of ECG Intervals Figure 4. 37 In an effort to explain these different results, the T-P segment of the isoelectric line was measured. It was found that this segment increased with age in all groups, thus accounting for the decreased interval times with a slower heart rate. The total cycle length (P-wave to P-wave) of the exercise groups increased, while the seden- tary group remained essentially the same. This is explained by the slower heart rate and lengthened QRS interval in the conditioned animals. TABLE VIII COMPARISON OF MEAN T-P SEGMENTS AND MEAN TOTAL CYCLE LENGTHS (SECONDS) Mean T-P Segment Mean Total Cycle Group (Before) (After) (Before) (After) A .018 .033 .146 .159 B .022 .035 .158 .172 C .018 .032 .152 .150 Intercorrelations. The fact that no relationship was found between the ECG's and heart rate, heart weight, and all-out swim time shows clearly the individuality of each animal. Blouin8 also found no relationship between heart rate and ECG intervals of dogs. 8Leonard Thomas Blouin, "Effects of Position and Anesthesia Upon the Electrocardiogram of the Normal Dog"(un- published Master's thesis, Michigan State University,l956). CHAPTER V SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS I. SUMMARY This study was designed for the purpose of studying the effects of prolonged conditioning on the electrocardio- grams of albino rats. The literature in regard to the ECG‘s of rats is limited and there seems to be no information.on the effects of exercise on small animal electrocardiograms. Most of the rat ECG literature relates to the effects of aging. The general opinion is that the intervals of the rat ECG increase with age, and slower heart rates are observed. The effects of conditioning on human ECG'S is reported. There is a difference of opinion in regard to the effects of prolonged training on the electrocardiograms. Some authorities find no qualitative changes with condi- tioning, while others found statistically significant effects. The latter maintain that the T-wave is larger in athletes, the P-wave is generally smaller, and the P-R and Q-T intervals are lengthened with conditioning. The use of Sodium Pentobarbital on animals seems to have no effect on the electrocardiogram according to the reported literature. 39 Forty-eight albino, weanling, male, litter-mate rats were divided into three experimental groups: Group A received a stock diet and twelve weeks of conditioning, Group B received a stock diet mixed with powdered whole milk, constituting 30% of their daily caloric intake, and conditioning, and Group C received a stock diet and remained sedentary throughout the experiment. Groups A and B were swum twice daily for equal periods in metal tanks filled with 13" to 14" of water. Water temperature was maintained at 360 C to 370 C. Electrocardiograms were recorded from the three standard leads before and after the twelve weeks of condi- tioning. Two recording instruments were used. A Sanborn direct-writer was used for the initial pick-up and an Oscilloscope with a polaroid camera mounted on the screen was hooked into the direct writer and served as the second test device. Correlations and "t's" were computed on the data from these instruments. The results showed that the Oscilloscope gave the more accurate record of the rat ECG and, therefore, was used for the final test. All final analyses were computed from the Oscilloscope records. The following ECG data were collected: P, R, S, and T-wave amplitudes, and P-R,.QRS, and R-T intervals. Meas- urements were taken with vernier caliphers and recorded in millimeters. The amplitudes were converted to millivolts and the intervals to seconds. 40 Heart rates were computed before and after condi- tioning. All-out swim times were obtained by swimming each animal with six per cent of his body weight attached. The animals were sacrificed, dissected, and body organ weights tabulated. vectors were computed from Leads I and III. F-ratios were computed on the'"pre-condition" vectors and intervals, the "post-condition" vectors and intervals, and on the dif- ferences" from pre-conditioning to post-conditioning. Using the "t" test, the means of the "individual differences" between Groups A and C were compared. Correlations were computed on the ECG data and heart weight, heart rate after conditioning, and all-out swim times. II. CONCLUSIONS The following conclusions are derived from the data reported in this paper: 1. The direct writer is not adequate for recording the electrocardiograms of rats. (The use of the Oscilloscope gives a more accurate reproduction of the rat ECG. 2. The heart rate of the rat decreases with age and is slower in rats receiving exercise. 3. P-wave and T-wave magnitudes of rats decrease with age. Conditioning tends to retard the drop. 41 The QRS complex magnitude is increased or maintained by conditioning, while in a sedentary life this magnitude is reduced. The direction of the electrical force in the rat's heart changes with age regardless of the effect of conditioning in the P and T-waves. The change noted in the QRS complex is not as marked in the conditioned animals as that of the sedentary group. The P-R and R-T intervals decrease with age, conditioning having no effect on the P-R; but retarding the decrease in the R-T interval. The QRS interval lengthens slightly with condi- tioning, and decreases with a sedentary life. There is diversified opinion in regard to the effects of conditioning on the human ECG. III. RECOMMENDATIONS The following recommendations are made for further study in this area: 1. A similar experiment should be conducted by exercising rats on a treadmill at two different intensities. This would allow control of work output. For additional studies using swimming for the exercise, the use of deeper tanks would provide 42 a better control for the exercise. Also the use of round containers would be advisable as the animals soon learn to rest in the corners of a rectangular tank. A study of older animals with the design of this investigation would give more light on the effects conditioning has upon the aging heart. BIBLIOGRAPHY BIBLIOGRAPHY Books Cureton, T. K. Ph sical Fitness of Champion Athletes. Urbana: UnIversiEy o? IIlinois Press, I951. Katz, Louis Nelson. Electrocardiography. Philadelphia: Lea and Febiger, 1946. McNemar, Quinn. Psychological Statistics. New York: John Wiley and Sons, Inc.; LonHOn: *Chapman and Hall, Limited, 1955. Periodicals Beckner, George L. and Travis, Winsor. '"Cardiovascular Adaptations to Prolonged Physical Effort," Circulation, 9:835-846, June, 1954. Berg, Benjamin. ‘"The Electrocardiogram in Aging Rats," Journal of Gerontology, 10:420-423, October, 1953. Ensor, Charles R. ‘"The Electrocardiogram of Rats on Vitamin E Deficiency," American Journal 93 Physiology, 147:477-479, November, I946. Ershoff, Benjamin H. "Beneficial Effect of Liver Feeding on Swimming Capacity of Rats in Cold Water " Societ for Experimental Biology and Medicine, 772488-391, T951- Hundle , James M., Ashburn, L. L., and Sebrell, W. H. 'The Electrocardiogram in Chronic Thiamine Deficienc in Rats," American Journal of Physiology, 144:404-41 , August, 1945. Jackson, Charles E. and Winsor, Travis. '"Aids for Deter- termining Magnitude and Direction of Electric Axes of the ECG," Circulation, 1:975-981, April, 1950. Rappaport, Maurice B. and Rappaport, Irving. '"Electrocardio- graphic Considerations in Small Animal Investigations," American Heart Journal, 26:662-680, November, 1943. 45 Rasch, Philip J., gt al. ‘"An Electrocardiographic Study of United States OIympic Free Style Wrestlers," Research Quarterly, 29:46-53, March, 1958. Simonson, Ernest, M.D. and Keys, Ancel, Ph.D. '"An Electro- cardiographic Exercise Test: Changes in the Scalar ECG and in the Mean Spatial QRS and T vectors in Two Types of Exercise: Effects of Absolute and Relative Body Weight and Comment on Normal Standards," American Heart Journal, 52:83-105, July, 1956. ' Tung, C. L., et 2t.'"The Hearts of Ricksha Pullers: A Study of the ETfect of Chronic Exertion on the Cardiovascular System," American Heart Journal, 10:79-100, October, 193 . Tuttle, W. W. and Korns, Horace M. "Electrocardiographic Observations on Athletes Before and After a Season of Physical Training American Heart Journal, 21: 104-107, January, 1941. Waller, Robert K. and Charipper, Harry A. "Electrocardio- graphic Observations in Normal Throidectomized and Thiourea Treated Rats," American Journal of the Medical Sgiences, 210:443-452, OCEOber, 19357—- Wilbur, Charles G. '"Some Factors Which are Correlated with Swimming Capacity in Guinea Pigs," Journal 93 Applied Physiology, 16:199-203, March, I959. Unpublished Material Blouin, Leonard Thomas. '"Effects of Position and Anesthesia upon the Electrocardiogram of the Normal Dog." Un- published Master's thesis, Michigan State University, East Lansing, Michigan, 1956. Foerch, Richard L. '"A Comparison of Electrocardiographic Measurements of Athletes and Non-Athletes at Michigan State College." Unpublished Master's thesis, Michigan State College, East Lansing, Michigan, 1951. s ‘ ' , ~rfil—z ‘-",-"' r~"‘-":"f'\"‘f\| bUEEEr- I CI. E_I :,_’.,..'Ll 3'5 ' - It -u':-..\1‘IU|1 ‘ - ""u L“ "HH.-FETCH L'kULLL‘uI' bk— l-L’ \1'-. '51 ILII‘ MILHIGAN SIAIL ‘LIIVI‘\E'.II\SATY EAST LANSING, MiCHzGAN APPENDIX APPENDIX A CONVERSION FORMULAS USED IN THIS EXPERIMENT Conversion of picture size to actual screen size: Actual size of screen--100mm. Picture size of screen--54.4mm. 1.84 x picture measure = actual screen Size Conversion to millivolts(mV): Pictures: calibrations used: 27mm. lmV (.0370) 28m. = lmV (.03 7) 29mm. = lmV .03 5 calibration x measure = mV' Electrocardiograph: calibration used: 15mm. = lmV (.0667) calibration x measure = mV Conversion to seconds: Pictures: sweep time = 50 milliseconds/hm. 50 milliseconds/Cm. = .005 sec./mm. .005 x measure = interval in seconds Electrocardiograph: speed of machine (actual) = 96.2mm./Sec. 1 sec. __ . 4 . C 96.2mm./Sec. 010 sec /hm .0104 x measure = interval in seconds APPENDIX B SWIM TIMES, HEART RATES, AND HEART WEIGHTS Animal Swim Time Heart Rate Heart Rate Heart Weight Number (sec) (before) (after) (grams) 1 312 420 402 1.407 2 768 468 366 1.433 4 400 420 372 1.303 6 277 420 408 1.555 7 212 450 354 1.495 8 358 456 354 1.265 9 287 450 426 1.357 12 212 510 420 1.469 13 360 534 456 1.438 15 300 426 348 1.600 16 270 498 438 1.401 17 505 414 426 1.621 18 324 504 420 1.488 19 335 480 378 1.459 20 569 408 360 1.350 21 444 474 378 1.401 23 337 432 384 , 1.478 24 470 432 324 1.219 25 494 462 384 1.436 26 172 402 390 1.470 APPENDIX B--Continued 49 33.11:: was“ 5:22.323; “7:15:33“ Hausa: 27 339 480 366 1.913 28 255 486 432 1.358 29 900 474 420 1.573 31 416 480 414 1.561 32 299 480 414 1.360 33 237 426 450 1.415 34 126 486 366 1.145 35 294 480 420 1.261 37 131 540 468 1.275 38 145 420 438 1.336 39 103 480 438 1.556 40 112 450 408 1.350 41 138 474 444 1.390 42 217 468 414 1.285 43 131 504 420 1.406 44 141 492 468 1.316 45 145 468 450 1.250 46 135 462 408 1.489 47 180 558 480 1.269 48 99 420 464 1.267 4—_v f; .3? T) I 4 I 7 _ ‘ MICHIGAN STATE UI‘IIVERSITY ‘77 INSTRUCTIONAL MATERIALS car-"t 57.91... COLLEGE OF EDUCATION . Ackerman 1959 F?“ :>c.. WITHDRAWN 1987 MICHIGAN STATE UNIVERSITY LIBRARIES I III ||||| II I | 31293 03055 9912