ACCELERATIONS OF A HYBRID III DUMMY HEAD RESULTING FROM
ROUNDHOUSE KICK IMPACTS AND THEIR IMPLICATIONS FOR CONCUSSIONS IN
BOYS AND GIRLS

By

Miguel Angel Narvaez

A DISSERTATION

Submitted to
Michigan State University
In partial fulfillment of the requirements for the degree of

DOCTOR OF PHILOSOPHY

Kinesiology

2011

ABSTRACT

ACCELERATIONS OF A HYBRID III DUMMY HEAD RESULTING FROM
ROUNDHOUSE KICK IMPACTS AND THEIR IMPLICATIONS FOR CONCUSSIONS IN
BOYS AND GIRLS

By

Miguel Angel Narvaez

The purposes of this study were to determine the magnitudes of linear acceleration of the
center of gravity and angular acceleration about the center of gravity on a Hybrid III dummy
head, as a result of being impacted with roundhouse kicks performed by children and to compare
these values with the same variables that are known in general to cause concussions. The
potential for roundhouse kicks performed by children to cause a concussion was examined.
Differences by age, gender and levels of expertise were also studied. Anthropometric data (body
mass index, flexibility, sitting height, standing height, weight, biacromial and bicristal widths
were also measured to study their effects on linear and angular accelerations.
Results indicated that children can exceed linear and angular acceleration thresholds for
concussions that have been established for NFL players. There are no known linear or angular
acceleration thresholds for children, but these may be smaller than those used for comparisons in
this study.
Results also showed that female participants generated higher linear and angular
acceleration values than male participants. Analyses revealed differences in linear and angular
accelerations by age group where older participants generated higher acceleration values than

younger participants. Skilled participants also generated greater maximal linear and angular
accelerations than beginners. Months of practice, standing height, weight, and flexibility
provided some explanation to the differences observed by age, gender, and skill level.
It is necessary to educate parents, martial arts instructors, and governing bodies about the
intrinsic risk for traumatic brain injuries, which has been reported to be similar to other contact
sports such as American football, boxing, and ice hockey. The use of head gear and mouth
guards is strongly recommended in practice and competition to reduce linear and angular
accelerations that the brain experiences as a result of an impact to the head to eliminate
concussions. The long term effects of single/multiple concussions in children are not known at
this time; however recent studies are identifying its negative effects on cognitive functions, thus,
it is suggested to reduce children exposure to these possible risks.

Copyright by
Miguel Angel Narvaez
2011

DEDICATION
I dedicate this work to my wife Xóchitl and my children Miguel, Marco and Michelle for
their love and support throughout these years. To my parents and siblings Ulises and Iskra whom
without them I would not be who I am. To all my friends, particularly Tony and Carmen
Benavides, and David and Karen Mota for their encouragement and guidance.

v

ACKNOWLEDGEMENTS

I wish to thank my committee members and advisors for their support, patience and
encouragement provided throughout my program and dissertation. Thank you Dr. Eugene
Brown, Dr. Marty Ewing, Dr. Dianne Ulibarri, Dr. Joey Eisenmann, Dr. Kirt Butler and Dr.
Cynthia Bir.
I would like to acknowledge the Consejo Nacional de Ciencia y Tecnología (CONACYT)
for granting the scholarships that supported my academic endeavors through my masters and
doctoral degrees.
I would like to give special thanks to Dr. Cynthia Bir and Nathan Dau at Wayne State
University for their technical and human assistance in completing the data collection portion of
this dissertation. This would not have been possible without their assistance.
I’m also thankful to all the faculty and staff in the Department of Kinesiology at Michigan
State University for providing not only a challenging academic environment but for offering
their friendship and support beyond expectations.

vi

TABLE OF CONTENTS

LIST OF TABLES ......................................................................................................................... ix

LIST OF FIGURES ....................................................................................................................... xi

LIST OF SYMBOLS or ABBREVIATIONS ............................................................................. xiii

CHAPTER I .................................................................................................................................... 1
Introduction ..................................................................................................................................... 1
Statement of the Problem ................................................................................................................ 6
Purpose of the Study ....................................................................................................................... 6
Significance of the Study ................................................................................................................ 7
Hypotheses ...................................................................................................................................... 8
Limitations ...................................................................................................................................... 9

CHAPTER II................................................................................................................................. 12
Kinematic and Kinetic Studies on Martial Arts Techniques ........................................................ 12
Concussions .................................................................................................................................. 17
Definitions of Injuries in Martial Arts .......................................................................................... 41
Injury Mechanisms in Martial Arts ............................................................................................... 43

CHAPTER III ............................................................................................................................... 46
Participants.................................................................................................................................... 46
Procedures ..................................................................................................................................... 49
Instrumentation and Setup ............................................................................................................ 49
Anthropometric Measurements..................................................................................................... 56

CHAPTER IV ............................................................................................................................... 57
Anthropometry .............................................................................................................................. 57
Performance Data ......................................................................................................................... 63
Tests of Null Hypotheses .............................................................................................................. 72

CHAPTER V ................................................................................................................................ 83
Linear Acceleration....................................................................................................................... 83
Angular Acceleration .................................................................................................................... 86
Severity Index (SI) and Head Injury Criteria (HIC) ..................................................................... 89

vii

Conclusions ................................................................................................................................... 90
Practical Implications ................................................................................................................... 91
Recommendations for Further Study ............................................................................................ 93

APPENDICES .............................................................................................................................. 95
Appendix A ................................................................................................................................... 96
Appendix B ................................................................................................................................... 96
Appendix C ................................................................................................................................... 99
Appendix D ................................................................................................................................. 103
Appendix E ................................................................................................................................. 105
Appendix F ................................................................................................................................. 108
Appendix G ................................................................................................................................. 110
Appendix H ................................................................................................................................. 111
Appendix I ………………………………………………………………………………….… 119

REFERENCES ........................................................................................................................... 122

viii

LIST OF TABLES

Table 1 Abbreviated Injury Scale (AIS) …....………………………………………………….. 38
Table 2 Injury Mechanisms per 1000 Athlete-Exposures (A-E) …........................................…. 44
Table 3 Injury mechanism of time-loss injuries per 1000 Athlete-Exposures (A-E) (Pieter et al.
1995) …..……………………………………………………………………………………….. 45
Table 4 Injury mechanism of cerebral concussions per 1000 Athlete-Exposures (A-E)………...45
Table 5 Age Groups and Number of Kicks ......…………………………………………………48
Table 6 Population Anthropometric Data and Flexibility Scores…………………………….….58
Table 7 Mean Values for Linear and Angular Accelerations, HIC, and SI by Participant………65
Table 8 Descriptive Statistics for Linear and Angular Acceleration, HIC and SI Overall and by
Gender…………………………………………………………………………………………....71
Table 9 Descriptive Statistics for Linear and Angular Acceleration, HIC and SI by Skill Level
……………………………………………………………………………………………………71
Table 10 Sample Pearson Correlation Coefficients (2-Tailed) Among Performance Parameters
and Injury Factors (n=171 roundhouse kicks) ……………………………………………….… 72
Table 11 Sample Pearson Correlation Coefficients (2-Tailed) for Mean Values, Among Age,
Experience, Anthropometry, Performance Parameters, and Injury Factors (n=171 roundhouse
kicks)…………………………………………………………………………………………..…72
Table 12 Sample Pearson Correlation Coefficients (2-Tailed) Among Age, Experience, and
Anthropometry (n=171 kicks)………………………………………………………………...…74
Table 13 Pearson Correlation Coefficients (2-Tailed) for Maximum Values per Participant,
Among Age, Experience, Anthropometry, Performance Parameters, and Injury Factors (n=18
participants) …………………………………………………………………………………….. 75
Table 14 Statistics for Maximum Linear Acceleration by Gender ……………………………...76
Table 15 Means and Standard Deviations for Maximum Angular Acceleration by Gender …... 77
Table 16 Linear Acceleration (LinAcc) and Age Group Descriptive Statistics ……………….. 77

ix

Table 17 Angular Acceleration (AngAcc) and Age Group Descriptive Statistics …………….. 78
Table 18 Means and Standard Deviations for Linear Acceleration by Skill Level ………….… 79
Table 19 Means and Standard Deviations for Maximum Angular Acceleration by Skill Level.. 79
Table 20 Linear Acceleration Regression Coefficients and Collinearity ……………………… 80
Table 21 Angular Acceleration Regression Coefficients and Collinearity ……………………. 80
Table 22 Linear Acceleration (Participants Exceeding 42 g’s) ……………………………...… 85
Table 23 Angular Acceleration (Participants Exceeding 2000 rad/sec2)………………………. 88

x

List of Figures

Figure 1. Experience of participants by age and gender (* indicates a black belt participant)… 49
Figure 2. Testing setup. ………………………………………………………………………… 50
Figure 3. Orientation of standardized dummy coordinate system. For interpretation of the
references to color in this and all other figures, the reader is referred to the electronic version of
this dissertation…………………………………………………………………….…………… 51
Figure 4. Headgear. …………………………………………………………………………….. 51
Figure 5. Foot pad used by participants to reduce the risk of injury during testing ….…..……. 52
Figure 6. Dummy head set at participant’s stance head height……………………………….… 52
Figure 7. Accelerometers and angular sensors mount…………………………………………...53
Figure 8. TDAS PRO modules…………………………………………………………………..54
Figure 9. TDAS software screen snapshot……………………………………………………….55
Figure 10. Participant roundhouse kick trial……………………………………………………..56
Figure 11. Participants’ height by age and gender……………………………………………….58
Figure 12. Participants’ weight by age and gender………………………………………………59
Figure 13. Participants’ sit and reach flexibility by age and gender……………………………..59
Figure 14. Participants’ body mass index by age and gender……………………………………60
Figure 15. Participants’ sitting height to standing height ratio by age and gender………………61
Figure 16. Participants’ biacromial to bicristal ratio by age and gender………………………...61
Figure 17. Participants’ sitting height to standing height ratio by skill level……………………62
Figure 18. Participants’ biacromial to bicristal ratio by skill level………………………………62
Figure 19. Participants’ Body Mass Index by skill level………………………………………...63

Figure 20. Linear acceleration values per trial by participant, low and high thresholds from
Pellman et al. (2003)……………………………………………………………………………..66

xi

Figure 21. Mean, minimum and maximum linear acceleration values by participant…………...67
Figure 22. Angular acceleration values per trial by participant. Low threshold from King et al.,
(2003), high threshold from Zhang, Dwarampudi, Yang, and King (2003)………………….… 68
Figure 23. Mean, minimum and maximum angular acceleration values by participant. Low
threshold from King et al., (2003), high threshold from Zhang, Dwarampudi, Yang, and King
(2003)…………………………………………………………………………………………….69

xii

KEY TO SYMBOLS OR ABBREVIATIONS

g gravitational force
gr gram
kg kilogram
2
kgm kilogram meter squared

m meter
2
m square meter

m/s meter per second
2
m/s meters per second squared

N Newton
Nm Newton meter
Ns Newton per second
2
rad/s radians per second squared

s seconds

xiii

CHAPTER I
Introduction
Martial arts had their origins within many ancient cultures; some records indicate their
existence as far back as 5000 years ago (Goldman, 1997). They were created as self-defense
systems against animals and assailants (World Taekwondo Federation, n.d.), and included unique
skills influenced by the local environment where they developed. In countries such as Japan,
karate, judo, and aikido flourished; in Korea, taekwondo and hapkido are commonly practiced,
while China’s wushu and tai chi are among the most known martial arts (Goldman, 1997;
Goodman, 2004). Some of these martial arts have transformed into competitive sports, and have
even been included as official sports in the Olympic program, such as judo in Tokyo in 1964,
and taekwondo in Sydney in 2000.
The popularity of martial arts around the world can be attributed to films, but also to
intrinsic benefits associated with their practice. As an example of this popularity, taekwondo has
a worldwide presence in over 182 countries (World Taekwondo Federation, n.d.). It is
recognized among the martial arts by its emphasis on the use of kicking over punching which
makes upwards to 70% of its basic techniques (Buschbacher & Shay, 1999; Kim, Chung, & Lee,
1999; Park & Seabourne, 1997; Zetaruk, Violan, Zurakowski, & Micheli, 2005). All martial arts
curricula include basic movements (stances, displacements, kicks, blocks, and punches), forms
(pre-established movement patterns), sparring (step and free style), and breaking (wooden
boards, tiles, and bricks) (Goldman, 1997; Goodman, 2004; Kim, 1995). A colored belt system is
used to classify its practitioners based on their skill proficiency. In this system, novices wear
white belts and black belts are reserved for advance practitioners (Goodman, 2004; Kim, 1995).

1

Some systems have a strong emphasis on kicking techniques, which has lead to the
development of a variety of kicks. Among the basic kicks are front, side, crescent or axe,
roundhouse, hook, and back (Goldman, 1997; Goodman, 2004; Kim, 1995; Kim, Chung, & Lee
1999; Park & Seabourne, 1997). Their complexity can be increased by combining different
kicks, and by adding turns and even jumps. Regardless of the nature of the kicks (individually or
in a combination), kicks can be classified based on their mechanics as circular or linear (Serina
& Lieu, 1991). Research on kicking technique usage in competition has shown a predominance
of circular techniques due to their quickness of execution and possibility to their ability to deliver
a powerful blow (Pieter & Pieter, 1995). Linear techniques have been reported to be slower and
less powerful, but still effective in specific situations, where they can decide a match by a
knockout (Kim, 1995; Kim, Chung, & Lee, 1999; World Taekwondo Federation (WTF), 2004).
Practitioners of different ages, gender, and physical abilities are attracted to martial arts
for various reasons. Park and Seabourne (1997) identify physical challenge, to learn self-defense,
to be physically active, and to have fun or socialize among these reasons. Similarly, research has
also provided evidence of other benefits associated with martial arts and taekwondo practice.
These include improvement of self-esteem, self-discipline, and confidence (Birrer, 1984;
Finkenberg, 1990; Konzak & Boudreau, 1984; Richman & Rehberg, 1986; Trulson, 1986; Weiss
& Petlichkoff, 1989). Furthermore, studies of fitness levels of martial arts practitioners have also
shown improvements in cardiovascular conditioning, anaerobic power, flexibility, and balance
(Bridge & Jones, 2005; Markovic, Misigoj-Durakovic, & Trninic, 2005; Melhim, 2001; Pieter,
1991). As a result of a combination of benefits attributed to taekwondo, along with media
exposure, participation in martial arts in the U.S. has been reported to be one million (Birrer &
Halbrook, 1988), one and a half million (Oler, Tomson, Pepe, Yoon, Branoff, & Branch, 1991),

2

two million (Wilkerson, 1997), and even eight million (Zetaruk, Violan, Zurakowski, & Micheli,
2005). With the significant level of development and popularity of martial arts, the U.S. has had
several Olympic and world champions throughout the years. Furthermore, it was indicated that
the majority of these participants are children, with females representing 20% of the practicing
population.
The wide age range of participants has favored the organization of free sparring
championships for different age categories and gender in all martial arts. In many martial arts’
free sparring competitions, full contact kicking and punching, with some restrictions, is allowed
between contestants (WTF, 2004; Goodman, 2004). In spite of these regulations, injuries are
common in martial arts competitions where protective equipment is minimal.
The most commonly reported injuries in martial arts are contusions, sprains, and strains
(Birrer, 1984; Birrer & Halbrock, 1988; Buschbacher & Shay, 1999; Wilkerson, 1997).
However, serious injuries such as concussions, paralysis, visceral rupture, and even fatalities
have also been recorded (Oler et al., 1991; Pieter, 1991; Powell, 2001; Quintana-Diaz & GiraltLopez, 1998; Siana, Borum, & Kryger, 1986; Wilkerson, 1997; Zetaruk, et al., 2005).
The number of head injuries reported by several researchers (Birrer, 1984; Jui-Chia, Lin,
& Esposito, 2006; Koh & Watkinson, 2002a; Siana et al., 1986) highlights the potential for
serious neurologic damage associated with these injuries. This finding is significant since
children make up a high percentage of the martial arts practicing population. Burke, Barfoot,
Bryant, Schneider, Kim, and Levin (2003) reported in their study that nearly 50% of the injuries
in a taekwondo tournament were to the head and neck region in spite of the fact that tournament
rules forbid blows to the face. Pieter and Zemper (1997a) have reported concussions to be the
second most common injury in their study on injuries sustained by children in a taekwondo

3

competition. Although a concise definition of concussion can be difficult, Powell (2001) defined
it as a “trauma induced alteration in mental status that may or may not involve a loss of
consciousness” (p. 307). The Congress of Neurologic Surgeons definition states that a
concussion is “a clinical syndrome characterized by the immediate and transient post-traumatic
impairment of neural function such as alteration of consciousness, disturbance of vision or
equilibrium due to brainstem involvement” (Powell & Barber-Foss, 1999, p.958). Regardless of
who provides the definition, a concussion is associated with a disruption of brain function and an
alteration of consciousness to some degree.
Zemper and Pieter (1994) reported that cerebral concussions are the most serious injuries
observed in taekwondo competition. They estimated a concussion rate of 5.2/1000 athleteexposures, which is 3.1 times higher than the rate seen in college football games based on
number of exposures. In another study (Pieter & Zemper, 1998) it was noted that concussions to
female athletes were all of a mild nature, whereas 16.7% of concussions in males were
considered severe, because these male athletes lost an average of 21 days or more of training
and/or competition per occurrence.
Koh and Watkinson (2002b) reported that in an international competition (where 32 male
and 32 female high skill level athletes participated, with an age range from 15 to 38 years) the
most dominant techniques that caused a head blow were the axe kick (51.4%), roundhouse and
turning-roundhouse kicks (31.4%), 360 spinning kick (11.4%), and back kick (5.7%). In another
study by Koh, Watkinson, and Yoon (2004), with a sample size of 2328 athletes (676 females
and 1652 males between the ages of 11 to 19 years, with advanced skill level), it was reported
that among concussed competitors who experienced ringing in the ear (1009 cases), 61% of the
impacts were made on the side of the head and face, 16% on the lower jaw, 13% on the back of

4

the head, and 10% on the center of the face; and the kicks that caused it were in 50% of cases
roundhouse kicks, 33% axe kicks, 8% back kicks, and 6% spinning kicks. Research conducted
by Koh and Watkinson (2002a) in a Canadian championship (which included 139 males and 73
females, with age ranging from 14 to 24 years) and in Korea by Koh and Cassidy (2004) (with
2328 competitors, where 391 male and 171 female studied at high school level and 810 male and
301 female did so at the middle level; their ages ranging between 11 and 19 years and classified
as possessing advanced skill levels) using the same methodology also showed similar findings
among these three studies.
Aside from the acute symptoms, concussions have been known to have long term effects
on the individuals that suffer them, regardless of their number and severity. Powell (2001);
Wojtys, Hovda, Landry, Boland, Lovell, McCrea, and Minkoff (1999); and Zemper and Pieter
(1994) recognized the cumulative effects of concussion and cited reductions of memory function
and information processing capacity when subjects suffered a concussion, even without losing
consciousness. Johnston, McCrory, Mohtadi, and Meeuwisse (2001) also identified memory; and
the abilities to learn new things, plan, and switch mental “set”; as being affected after a mild
concussion. Similarly, they reported a reduction of information processing speed and reduced
attention as other effects of this type of injury.
In spite of the known potential risks for long term effects on the central nervous system
of concussive injuries in martial arts; the high incidence of these injuries in the activity; and the
availability of studies that have described the kinetics, kinematics, and impact forces of the
kicks; no studies have addressed the direct effects of contact accelerations of the most common
martial arts kicks on the risk of suffering a concussion.

5

Statement of the Problem
Injuries are an intrinsic factor of sports participation and their effects range from being
brief and non-relevant to permanent conditions and career ending, and in extreme cases even
death. Contact sports such as martial arts expose their participants to competitive situations
where severe injuries to the head can occur, and the long term effects of these injuries should not
be ignored, especially when participants are exposed to these situations at early ages where the
risk of sustaining these injuries and their long term effects may be even greater.
In martial arts, there is a paucity of information regarding the mechanisms of injuries to
the head, effects of impacts on the cognitive and motor abilities of individuals after receiving
kicks or punches to the head, impact mechanics of techniques, and/or advantages of requiring the
use of head gear in competition. Thus, there is a need to investigate and compare selected
kinematic variables and the response of the body to these stressors. An approach to this is to
study the kinematic variables resulting from basic kicking techniques. The roundhouse kick is a
technique that may provide an understanding of how a model head (from a humanoid model with
multi-directional biofidelity) responds to this type of impact and may provide insight into the
relationships between impact responses with known parameter values that are generally
associated with the appearance of symptoms of concussion.
Purpose of the Study
The purposes of this study were to determine the magnitudes of linear acceleration of the
center of gravity and angular acceleration about the center of gravity on a Hybrid III dummy
head, as a result of being impacted with a roundhouse kick, and to compare these values with the
same variables that are known in general to cause concussions. Thus, the potential for
roundhouse kicks to cause a concussion was examined, and recommendations to reduce the

6

incidence of this type of injury were made. Secondly, the roundhouse kicks to a Hybrid III
dummy head by martial arts practitioners of different ages, levels of expertise, and gender were
studied. Body mass index, flexibility, sitting to standing height, and biacromial to bicristal ratios
were also used to study their effects on linear and angular accelerations.
Significance of the Study
Several biomechanics studies have been conducted to analyze techniques in martial arts,
and in particular in taekwondo. Most of these studies have focused on the kinematics and
kinetics of kicking and the differences in performances of individuals with various skill levels.
Variations of the front kick, and mostly its kinematic variables, have been studied by Bercades
and Pieter (2006); Kim (1993); Park (1989); Sorensen, Zacho, Simonsen, Dyhre-Poulsen, and
Klausen (1996); Tsai and Huang (2000); and Yates (2005). More complex kicking techniques
such as the roundhouse kick, side kick, back kick, and hook kick have also been studied by Joon,
Guk, Jong, and Kyu (1987); Kim, Yamaguchi, and Hinrichs (2004); Kong, Luk, and Hong
(2000); Lan, Wang, Wang, Ko, and Huang (2000); Liu, Tan, An, and Wang (2000); Luk and
Hong (2000); Shiang and Chou (1998); and Wohlin (1989). Kinetic variables have been the
focus of the studies by Lee and Lee (1999); Lee, Jung, Shin, and Lee (2001); Neal and Landeo
(1998); Pieter and Pieter (1995); Serina and Lieu (1991); Tsai, and Huang (2000); and Sidthilaw
(1996).
Studies that have focused on the dynamics of general kicking tasks as well as computer
simulations have been conducted by Barfield, Kirkendall, and Yu (2002); Choi, Kim, So, Yi, and
Kim (2002); Kim, Yamaguchi, and Hinrichs (2004); Lindbeck (1983); and Putnam (1991).
Biomechanical studies that addressed the impact of kicks and their risk of imparting
injuries have not been found in the literature. Only a few studies attempted to assess the risk of

7

head injuries in martial arts: Moffitt (1995) evaluated the impact response of martial arts
headgear to simulated kicks and falls, Hrysomallis and McLaughlin (1999) assessed the risk of
head injuries from falls on taekwondo mats, and Chi (2005) proposed the use of wearable force
sensors in martial arts.
In general, all of these studies had small sample sizes; most of them included only male
practitioners with high skill levels, and data collection was based on videography. There has not
been any studies that attempted to estimate the contact force to the head generated by a kick of a
martial arts practitioner and evaluate its risk of injury to the central nervous system, much less as
a result of a roundhouse kick, which is one of the most commonly used kicks in the martial arts
curriculum. The roundhouse is the most frequently used kick in competition, and it has been
reported to cause concussions in taekwondo and martial arts competition. By understanding the
potential for martial arts kicks to cause concussions, adequate measures may be taken to reduce
the risks of this type of injuries in competition and practice, and may make the participation of
athletes safer.
Hypotheses
To address the stated research problems, the following hypotheses were investigated:
1) There will be no difference between maximum impact linear accelerations of the dummy head
generated via roundhouse kicks and acceleration values known to cause concussions in humans.
2) There will be no difference between maximum impact angular accelerations of the dummy
head generated via roundhouse kicks and acceleration values known to cause concussions in
humans.
3) Roundhouse kicks by male participants will not generate greater maximum impact linear
accelerations of the dummy head than female participants.

8

4) Roundhouse kicks by male participants will not generate greater maximum impact angular
accelerations of the dummy head than female participants.
5) Older participants’ roundhouse kicks will not generate greater maximum impact linear
accelerations of the dummy head than younger participants.
6) Older participants’ roundhouse kicks will not generate greater maximum impact angular
accelerations of the dummy head than younger participants.
7) Skilled participants’ roundhouse kicks will not generate greater maximum impact linear
accelerations of the dummy head than less skilled participants.
8) Skilled participants’ roundhouse kicks will not generate greater maximum impact angular
accelerations of the dummy head than less skilled participants.
Limitations
Martial arts practitioners were recruited from local gymnasia and may not represent the
whole martial arts population.
Participants from martial arts which emphasize kicking over punching may have
performed differently than those that use hands techniques more often.
Accelerometer measurements may be affected by the fact that the Hybrid III female head
model has a metal core, and is covered by a hard rubber-like material, thus making it a hard
surface to kick, and may cause some discomfort in some participants potentially resulting in less
than maximum velocity kicks. However it is designed to react to external forces as a human head
would under the same circumstances.
No linear or angular accelerations on thresholds known to cause concussion are available
to assess the risk of impacts in children; thresholds used in this study were obtained from adult

9

NFL players. It may be possible that linear and angular thresholds for children be lower than
these values.
The automotive industry has been developing and using various humanoid models
throughout the years to understand the responses of humans in car collisions as an alternative for
using human cadavers. Kinematic data such as linear and angular accelerations have been
measured and calculated to establish safety guidelines that rule automotive design, but are not
extensive to other fields that relate to human injuries. It was not until the creation of the National
Operating Committee on Standards for Athletic Equipment (NOCSAE) (Overland Park, Kansas,
1969) and its initial testing of football helmets, that data on the head behavior during and after an
impact in sports and recreational activities were available. In spite of these efforts to understand
the mechanisms of injury to the head, and particularly the effects of impacts to the head, there
have been no studies on the effects of punching and/or kicking in martial arts that can relate
acceleration values of the head with their potential for concussion. Thus, data collected in the
current research will provide the first data under this perspective.
The testing position of the dummy (see CHAPTER III: Methods) can be considered a
limitation because it will not fall back as a person would as a result of the impact. The setup used
was considered adequate to hold the dummy head in place (Nathan Dau, personal
communication, March 2009), to allow as much movement as possible of the head and neck after
impact, and reduce the chances of injury to the participants if the dummy were not movable at
all. When a person is struck in the head, regardless of the direction of the impact (front, back, or
side), the head tends to rotate about the neck as a result of the impact. Thus, a system for the
dummy head where support is simulated by the neck is more natural than holding the head from
the top, where an impact to the head would result in a rotation about the top of the head.

10

Additionally, the sample size, the small number of female participants, the small number
of advanced level participants, and possible negative effects related to the setup on participants’
willingness to exert maximal kicking impact against a padded metal device contribute to the
limitations.

11

CHAPTER II
Literature Review
Kinematic and Kinetic Studies on Martial Arts Techniques
Park (1989) investigated kinematic and kinetic parameters of front kicks by taekwondo
practitioners with their trunk in three different positions (slightly forward, vertical, and slightly
back). There were 18 male black belt taekwondo participants with a mean age of 29.5 years.
Subjects were filmed with a 16 mm camera at a 100 frames per second while each kicked with
the right foot and maintained his supporting foot on an AMTI force platform. Quadrant markers
were positioned on the lateral side of the right toe, ankle, knee, and hip joints. Digitizing was
done via a Sonic Digitizer interfaced to an XT-type computer. Nineteen landmarks were
digitized. Linear and angular kinematics were calculated from the digitized data. Muscle
moments at the right ankle, knee, and hip joints were computed, and ground reaction forces were
also stored in the computer system. The results pointed to a reduction in movement time of the
kicks as a result of positioning the trunk backward immediately before the kick. In practice
situations, the use of this kick variation is emphasized in order to prevent counter-attacks from
opponents. Maximum resultant linear velocities of the kicking foot were between 11.03 to 11.28
m/s in all kicks, indicating that there was no significant difference observed in the front kicks
with the three different trunk positions. Mean maximal horizontal acceleration of the kicking foot
2
for the three kicks ranged from 66.51 to 68.21 m/s . The mean maximal vertical acceleration
2
values were between 94.64 to 108.29 m/s . Although there were no significant differences in

vertical acceleration among kicks, it was observed that there was a difference for the mean
maximal vertical acceleration favoring the trunk backward position. There was no significant

12

difference in the peak muscle moments at the hip, knee, and ankle joints among the kicks. The
mean values ranged from 156.82 to 169.63 Nm for the hip, 26.68 to 33.61 Nm for the knee, and
5.72 to 6.76 Nm for the ankle. No significant differences were observed in the mean maximum
vertical ground reaction forces of the supporting foot during the three kicks. These values were
between 934.1 to 986 N.
Kim (1993) analyzed the kinematics and kinetics of the front thrust kick. Five novice and
five expert male practitioners participated in the study. The age of the participants ranged from
19 to 22 years, and their height ranged from 1.55 to 1.78 m. Their weight ranged from 43.6 to
74.2 kg. Data were collected via high-speed camera at 200 frames per second. Impulse was
measured via Kynar Piezo film mounted on a Lexan plastic sheet as a target. Ten joint markers
were placed on the right side of the subjects, but only the heel, ankle, 5

th

metatarso-phalangeal

joint, knee, and hip were used in the study. Anthropometric measurements of height and weight,
and length of the foot, shank, thigh, and trunk were taken.
Linear kinematic peak resultant variables were studied for the metatarso-phalangeal
marker, as well as linear displacement of the hip marker. Angular kinematics were analyzed for
the trunk, shank, and thigh. There was no significant difference in the total kicking time between
novices (0.223 s) and experts (0.230 s). This time was calculated from the film, and was
measured from the moment the kicking foot left the ground to the moment the foot made contact
with the target. There was also no significant difference when comparing both groups in total
impulse of the kicking leg before the foot left the ground; experts’ mean was 19.29 Ns and
novices’ mean was 18.68 Ns. Mean peak resultant linear velocities of the kicking foot were also
not significantly different with values of 10.6 m/s for novices and 11.28 m/s for experts.
Similarly maximum resultant linear accelerations of the kicking foot also did not show a

13

2
significant difference between groups, where experts exhibited a mean of 632.97 m/s and
2
novices a mean of 592.48 m/s . Overall, the study showed that there were no differences in the

kinematic variables and impulses between novice and expert practitioners.
Lan and colleagues (2000) studied the kinematics of three taekwondo kicking
movements. The kicks included were the roundhouse, back round, and back. The participants
were five highly skilled female practitioners with a mean age of 21 years, height of 1.62 m,
weight of 52.4 kg, and practice experience of ten years. Two high speed video cameras filming at
120 Hz were used to record the performances of the kicks. Digitizing was done using a peak
Motus system, and parameters from Dempster and Gaughran’s (1967) data were used to estimate
centers of masses. Their results indicated the following: the maximum resultant foot velocity was
observed on the roundhouse kick (mean maximum foot velocity for all three types of kicks was
37.67 m/s); movement time was shorter for the back round kick (mean movement time for all
three types of kicks was 0.1985 seconds), and the smallest knee angle of the kicking leg was
observed on the back kick during the preparation phase (mean minimum knee angle for all three
kicks was 36.21 degrees). There was no significant differences among the three kicks when
measuring the foot velocities at the moment of impact with the target (mean of 2.66 m/s for all
three types of kicks). It was also observed that the roundhouse kick was a whip-like movement;
whereas the back round and back kicks do not follow this pattern. It was inferred that shorter
movement time explains the more frequent use of a particular kicking technique in competition.
Kong and colleagues (2000) compared kinematic variables of roundhouse kicks being
performed alternately with the front and back positioned extremities while maintaining a sparring
stance. Eight male subjects with a mean age of 26.1 years, height of 1.69 m, and weight of 60.68

14

kg participated in the study. Their training experience mean was 6.6 years. Two high speed
cameras recorded the kicks at 120 Hz. Four reflective markers were placed on the major joints of
the lower extremity (hip, knee, ankle, and fifth metatarsal). A start signal was given and an
accelerometer recorded the moment of impact with the target. Significant differences were
observed in movement time, maximum resultant linear velocity of the ankle, and maximum
resultant linear velocity of the knee (mean maximum linear velocity of the ankle for the front
positioned leg was 18.83 m/s; whereas, the mean maximum linear velocity of the back positioned
leg was 14.56 m/s; the mean maximum linear velocity of the knee was 9 m/s for the front
positioned leg and 14.56 m/s for the back positioned leg). Movement time for the front
positioned leg was an average 0.73 s; whereas the back positioned leg took 0.83 s for the foot to
reach its target. They concluded that having a fast kick may be convenient to score points due to
the fast movement time, but also acknowledged that a powerful kick associated with a greater
momentum such as kicking with the back positioned leg may be also useful in competition; thus,
they recommended developing strategies that included the use of both techniques.
Wohlin’s (1989) study focused on the kinematics and kinetics of the whole body of a
practitioner performing a hook kick. There were two male and one female participants in the
study; all were highly skilled and ranged in age from 25 to 31 years. Data were collected via two
high speed cameras sampling at 150 fields per second. Joint markers were placed on the right
side of the subjects’ upper and lower extremities. Anthropometric data (height, weight, and
segmental lengths) were also collected. Video fields were digitized using a FILMADATA
motion analysis program and linear and angular kinematic and kinetic data were generated. The
2
rotational inertia of the body at the end of the push-off phase ranged from 5.61 kgm to 7.69
2
2
2
kgm ; when normalized for subjects’ masses, ranged from 0.078 m to 0.09 m . Anterior-

15

posterior dimensions of the base of support during the push-off phase also varied (0.57 to 0.82m)
from participant to participant but did not seem to be related to the height of the subjects. Total
peak resultant velocities of the metatarso-phalangeal joint at target contact ranged from 12.4 to
15.5 m/s. Total movement times for the kick for all participants ranged from 0.63 to 0.71 s; it
was noted that participants tended to keep the upper body segments as close as possible to the
trunk which allowed them to increase the velocity of the rotational movement, thus generating
faster kicks. The analyses also provided insight into the acceleration sequence of the thigh and
shank; and it appeared to be similar to those found in other kicking techniques, where the thigh
reached its maximum acceleration before the shank, and occurred before contact with the target.
Once maximum acceleration is achieved by the thigh, it started to decelerate, and the shank
followed in reaching its maximum acceleration, also prior to contact with the target.
The study by Tsai and Huang (2000) focused on the kinetic analysis of the taekwondo
axe kick. There were 20 male participants, with a mean experience of 6.6 years and a mean age
of 17.1 years; their mean height was 168.8 cm, and their mean weight was 59.9 kg. Participants’
data were collected from one foot on each of two Kistler force platforms with a sampling
frequency of 600 Hz. The mean of the total movement time of the axe kick was 0.88 s with a
range between 0.795 and 1.06 s. For the kicking leg the mean peak vertical ground reaction force
normalized to body weight was 1.46 with a range between 2.20 and 0.96. Mean vertical impulse
of the kicking leg prior to the kick was 227.7 Ns, while the horizontal impulse was 69.1 Ns. For
the support leg the mean peak vertical ground reaction force normalized to body weight was 1.79
with a range between 2.18 and 1.39. Mean vertical impulse of the kicking leg was 104 Ns with a
range between 155.9 and 70.6 Ns. No relationship was established between ground reaction
forces at the moment the kicking foot left the ground and contact force at the target. However,

16

findings indicate a negative correlation between peak anterior-posterior force of the kicking foot
and movement time.
Waliko, Viano, and Bir (2005) studied the risk of head injury from translational and
rotational acceleration from punches to the jaw of a Hybrid III dummy. There were seven
participants, all Olympic level boxers from five different weight categories. The results indicated
a correlation between punch force and weight class (r = 0.0539). The mean force applied was
876 N. Translational and angular accelerations also were found to correlate to weight class (r =
0.432) and (r = 0.524), respectively. Mean linear acceleration was 58 g’s with a standard
deviation of 13 and mean angular acceleration was 6343 rad/sec2 with a standard deviation of
1789. The mean HIC from all punches was 71 with a standard deviation of 49, similarly this
showed a positive correlation with boxers’ weight (r = 0.672). The researchers concluded that
“the acceleration levels may be sufficient to cause some level of head injury if multiple punches
are landed”. They also suggested that rotational accelerations may be the most important factor
for concussions, indicating that findings were consistent with levels found in concussed
professional football players.
Concussions
Koh, Cassidy, and Watkinson (2003) studied the incidence of concussion in contact
sports, and conducted a systematic review of evidence. The authors’ purpose was to estimate the
incidence of concussion in contact sports, through an analysis of data contained in the literature
available between 1985 and 2000. The researchers’ inclusion criteria was based on documented
incidence of concussions in the sports of American football, boxing, ice hockey, judo, karate,
taekwondo, rugby, and soccer, all being defined as contact sports either by the possibility of
colliding with other players or making contact with other implements, such as balls (e.g., heading

17

the ball in soccer).

The review included data from male and female athletes of all competitive

levels and ages, and also included information as to whether or not the injury occurred during
practice or competition situations. Additional criteria included evidence of the incidence of
injury to the head or brain, and relevant reports on concussion and mild traumatic brain injury or
diagnostic criteria used for concussion. Studies related to whiplash or spinal cord injury, facial
bone fracture, and soft tissue injuries were not included. Similarly, articles reporting only
prevalence, unique cases, or did not include risk ratios were also excluded. A total of 23 articles
were used in this review from an initial set of 127. Their findings indicated that, on the selected
team sports, ice hockey showed the highest incidence of concussion in male athletes at the high
school, college, and amateur adult levels, and American football had the second highest
incidence. Among the individual sports, boxing was found to exhibit the highest frequency of
concussion. However, the authors identify an issue with over estimating cases in this sport due to
a fact that in boxing a knockout and a technical knockout are defined as concussion. The
researchers were only able to identify a limited number of studies on female athletes, but were
able to identify that taekwondo shows the highest frequency of concussion regardless of age.
Schulz, Marshall, Mueller, Yang, Weaver, Kalsbeek, and Bowling (2004) studied the
incidence and risk factors for concussion in high school athletes in North Carolina. The purpose
of this study was to examine the incidence rate of sports-related concussions and to estimate the
association between history of previous concussion and concussion rate. The researchers used a
stratified cluster sample of 15802 athletes from the North Carolina High School Athletic
Association, representing 12 sports. The sample included football (boys), cheerleading (girls),
wrestling (boys), volleyball (girls), baseball (boys), softball (girls), basketball (boys and girls),
soccer (boys and girls), and track (boys and girls), and the selected teams were followed for a

18

period of three years. The functional definition of concussion for the study was a “clinical
syndrome characterized by immediate and transient post-traumatic impairment of neural
functions, such as alteration of consciousness, disturbance of vision, equilibrium, etc., due to
brain stem involvement” (p. 938). A concussion report was a two-step process; one provided
information on the type of injury, and the second, provided information about signs and
symptoms associated with a concussion. Concussion incidence rates were defined for athletegame, athlete-practice, and athlete-exposure. A regression model included sport, body mass
index (BMI), year in school, calendar time, school size, and highest educational level attainment
by the head coach. Sports were classified as contact, limited contact, and non-contact. An
alternate classification grouped these sports as collision and non-collision.
From the 2750 injuries reported, only 206 were properly documented concussions, and
only 8% of them resulted in loss of consciousness. There were 124 more concussions that were
identified after reviewing injury forms. The results indicated the highest concussion rate overall
and during competition was observed in football. Conversely, cheerleading had the highest rate
in practice. Previous concussions were also a strong predictor for concussion rate in addition to
participation in contact sports, being in the bottom quintile of body mass indexes, and being in
9th grade.
Wojtys, Hovda, Landry, Boland, Lovell, McCrea, and Minkoff (1999) reported their
findings on concussion in sports. The authors acknowledge that a concussion is a form of
traumatic brain injury and defined it as:
“Any alteration in cerebral function caused by a direct or indirect (rotation) force transmitted to
the head resulting in one or more of the following signs or symptoms: a brief loss of
consciousness, light-headedness, vertigo, cognitive and memory dysfunction, tinnitus, blurred

19

vision, difficulty concentrating, amnesia, headache, nausea, vomiting, photophobia, or a balance
disturbance” (p. 677).
They also recognize that there may be delayed signs and symptoms such as “sleep
irregularities, fatigue, personality changes, inability to perform daily activities, depression, or
lethargy” (p. 677). They pointed out that there was a lack of a uniform consensus on how to
classify concussions. However, it was agreed that an early diagnosis will be helpful in
determining the time needed to recover, the effect of the second impact syndrome, and also the
cumulative effects of concussions over time. The authors explained some neurophysiologic
responses of the brain after a concussion, citing among these the “injury-induced vulnerability”
that describes the vulnerability of the neurons after a head injury to minor changes in cerebral
blood flow, intracranial pressure, and apnea that may lead to cellular death. They also
commented on the evidence of a metabolic dysfunction post-concussion that maintains this state
characterized by an increase in the demand for glucose, and a reduction in cerebral blood flow.
This response has also been observed in studies on mildly concussed animals; and in humans that
have experienced severe head injuries. The duration of this condition is not known in humans,
but in other species (i.e., rodents) it has been observed to last as long as ten days. Among their
recommendations for diagnosis were evaluations on the field, and on the bench, with a
neurologic and neuropsychologic approach. As a complement to these evaluations, it was also
recommended to have a baseline neuropsychologic assessment of the athlete so it can be used to
compare performances after the injury. Criteria for return to play was also discussed and it was
recommended that only when there were no signs and symptoms after 15 minutes of the collision
or impact, and there was a normal neurologic evaluation and no loss of consciousness, then
return to play the same day may be possible. However, if there was a loss of consciousness,

20

headaches were present, there was memory loss or other impairments; the player should not
return to play.
Covassin, Swanik, and Sachs (2003a) explored the topic of epidemiological
considerations of concussions among intercollegiate athletes. In this study the authors compared
the incidence of concussions among 15 different collegiate sports. They used data from the
National Collegiate Athletic Association (NCAA) Injury Surveillance System (ISS), and
considered data from 3535 team-seasons in a three year period. It is important to mention that all
the data in this system were recorded by certified athletic trainers from the participating
institutions throughout each sport season. The authors highlight the lack of agreement on the
definition of a concussion. However, they cite two definitions that are commonly accepted. One
by the American Medical Association and the Committee of Head Injury Nomenclature of the
Congress of Neurological Surgeons that states “a concussion as a clinical syndrome
characterized by the immediate and transient post-traumatic impairment of neurological function
(such as alteration of consciousness, disturbance of vision and equilibrium), due to brainstem
involvement” (p.13). The second, by the Quality Standards Subcommittee of the American
Academy of Neurology, indicates that “cerebral concussions are altered mental states that may or
may not include loss of consciousness” (p.13), and agreeing that amnesia and confusion are
symptoms of concussions. After analyzing the data, their findings indicate that, from a total of
40547 injuries suffered by men and women, 6.2% of them were concussions. Five percent of the
concussions (1224/24480) occurred during practice and 8% (1278/15975) during games. The
breakdown by gender indicated that female occurrences were 3.3% during practices and 8.9%
during games, whereas for males, the percentages were 5.5% and 7.7%, respectively. Sports like
football, soccer, ice hockey, lacrosse, wrestling, baseball, and basketball showed higher

21

incidence of concussions in game situations compared with practice. The same trend was
observed for females in soccer, basketball, and field hockey. It was concluded that overall
athletes participating in football, ice hockey, wrestling, soccer (male and female), and lacrosse
(male and female) are at the highest risk of suffering a concussion.
In another work by Covassin, Swanik, and Sachs (2003b), they compared sex differences
associated with the incidence of concussions among collegiate athletes in a three-year period,
using data from the NCAA ISS. The sports included in the study were soccer, lacrosse,
basketball, softball, baseball, and gymnastics. The authors recognized the cumulative effects of
concussions, and their long term negative consequences, and stressed the need to identify groups
of athletes at risk at every level of competition. In their paper, the authors suggested that an
increase in number of participants and anatomical differences (e.g., size, overall muscular
strength, greater ball-to-head size ratio in females, and weaker neck muscles in females) between
male and female athletes may be factors for the observed increase in number of concussion cases
in sports, thus the importance of conducting these types of studies.
The operational definition of concussion in this study (Covassin, Swanik, and Sachs,
2003b) was based on the NCAA ISS, which follows a grading scale. Grade 1 was characterized
by no loss of consciousness and short duration of post-traumatic amnesia. Grade 2 subjects
experienced loss of consciousness (for less than five minutes) and amnesia up to 30 minutes. For
grade 3, there was a loss of consciousness for more than five minutes and extended amnesia. The
researchers also defined injury rate as the ratio of the number of injuries in a specific sport to the
number of athlete-exposures in the same sport multiplied by a reference population of 1000
athlete-exposures. Their results indicated that concussions during practices represented 4.2%
(315 cases) of the total injuries observed during the three-year period the study was conducted

22

and in game situations this number was 7.8% (558 cases). A breakdown of the total number of
injuries by gender indicated that female athletes sustained 167 (3.6%) concussions during
practices and 304 (9.5%) during games. For males the numbers were 148 (5.2%) and 254 (6.4%),
respectively. Results also indicated that those sports considered contact sports presented a greater
risk for concussion, regardless of gender; thus lacrosse, soccer, and female basketball were
identified as sports with higher incidences. Similarly, those sports where there was no direct
contact between competitors presented the lowest risks for concussion. However, this may be
associated with the use of more protective equipment in these sports.
Female athletes suffered more concussions than males in soccer, basketball, lacrosse,
softball, and gymnastics. Some of these differences were associated with differences in the rules
of competition (lacrosse, softball) and the type of exercises (gymnastics), but others can be
directly associated with the morphology of the female athlete such as size, overall muscular
strength, and neck muscle strength.
Koh and Watkinson (2002a) studied the incidence and characteristics of head blows and
concussions in a Canadian national taekwondo championship. They analyzed videotapes of head
blows that had a potential for causing a mild traumatic brain injury. Their study included 139
male and 73 female competitors, ranging in ages from 14 to 24 years. They used the Mild
Traumatic Brain Injury Committee’s definition of concussion, which states “a traumatically
induced physiological disruption of brain function with a short period of altered or loss of
consciousness” (p.80). Their case definition of potential concussion included any athlete who
had experienced a direct blow to the head or face region which may have induced a physiological
disruption of the brain function. This disruption included loss of consciousness, loss of memory,
disorientation, and/or confusion. When there was a fracture to the face or skull as a result of a

23

direct blow, the case was excluded. The inclusion criteria considered 1) rapid movement of the
head as a result of the impact, 2) being stunned or dazed, 3) referee giving a standing eightcount, 4) opponent being awarded a point, 5) exhibiting gait unsteadiness, 6) hitting the head as a
result of falling; and 7) any loss of consciousness. There were observers on site during the
tournament that identified possible subjects, which were referred to the researchers to be
evaluated. Videotapes were observed later to code the cases.
After all the injuries where quantified by reviewing all the videos, injury incidence rates
were calculated using the number of injuries divided by the number of athlete-exposures (i.e.,
number of injuries divided by the number of minutes of exposure), as described by Zemper and
Pieter (1994). Inter-observer agreement was calculated and differences between groups of
concussed versus non-concussed were calculated. Six participants were characterized as having
experienced a concussion within the last 12 months. The rates for concussion were 53 per 1000
athlete-exposures, and 9 per 1000 minute-exposures. The highest frequencies were observed in
the lightest weight groups.
Researchers reported that 22 concussions occurred due to a direct kick to the head, which
represents a high incidence for the sport. A probable cause of these concussions was suggested to
be the rules granting a higher score (i.e., three points awarded for a kick to the head). When these
results were compared with other contact sports (i.e., soccer, football), it was observed that
taekwondo incidences of concussions were much higher.
Among the techniques used to cause a concussion were the roundhouse kick which was
used in 43% of the cases, axe kick in 29%, spinning kick in 14%, and back kick in 10%. The
offensive action proved to be the situation where the risk of a concussion was higher as
compared to defensive actions.

24

Guskievicz and Mihalik (2006) studied the biomechanics and pathomechanics of sportrelated concussions. The authors were aware that the term cerebral concussion is used
interchangeably with mild head injury, and that it is also the result of an:
“acceleration-deceleration mechanism in which a blow to the head or the head striking an object
results in one or more of the following conditions: headache, nausea, vomiting, dizziness,
balance problems, fatigue, trouble sleeping, drowsiness, sensitivity to light or noise, loss of
consciousness, blurred vision, difficulty remembering, or difficulty concentrating” (p.66).
The authors also made a reference to Hugenholtz and Richard’s (1982) work which
reported that a “linear acceleration of 80 to 90 g’s acting for more than four milliseconds can
result in a concussion” (p. 67). They further made references to other studies that indicated the
basic concussion mechanism was the acceleration and deceleration and/or rotation of the skull,
thus leading to categorize the mechanisms into head-contact injuries and head-movement
injuries. Furthermore, they also explained that mild traumatic head injury can result from a focal
injury or a diffuse injury. The authors also recognized several events that follow head trauma,
which included physiological, vascular, and biochemical changes that lead to irreversible brain
damage. Among these changes are the formation of oxygen-free radicals and lipid peroxidation,
and changes in neuropeptides and neurotransmitters, ischemia, and brain swelling; also a
reduction of intracellular pH, an increased cerebrospinal fluid, and even glycolytic increases, and
reduction of cerebral blood flow.
Zemper (2003) conducted a two year prospective study of relative risk of a second
cerebral concussion. The author pointed to the common presumption that an individual who has
incurred a cerebral concussion was at greater risk for sustaining another one, and also
underscored the lack of a risk ratio that could describe this relationship. He used the American

25

Academy of Neurology’s definition of concussion, which states that it is “a traumatically
induced alteration in mental status (e.g., confusion, amnesia) that may or may not involve loss of
consciousness” (p.654), and also considered the Concussion in Sport Group’s definition
proposed in 2001 as “a complex pathophysiological process affecting the brain, induced by
traumatic biomechanical forces” (p.654). The author highlighted the importance of studying the
risk of concussion in individuals who have a history of concussion, and its association with
amount of playing time and exposure time. His study included data from two high school
football and college seasons taken from a large national sample. Data from 89 high schools and
85 colleges from the 1997 and 1998 football seasons were collected from the Athletic Injury
Monitoring System (AIMS). The information included number of players that had a history of
concussion during the previous five years, any reports of injuries during practice and games, and
the severity of them. Concussions were reported following the aforementioned definition, and
also used the American Academy of Neurology scale, which ranges from “grade 1 indicating
transient confusion that resolves in less than 15 minutes; grade 2 indicating symptoms that last
longer than 15 minutes but there is no loss of consciousness; and grade 3 for any concussion
involving loss of consciousness” (p.655).
During the study period, there were 572 concussions, 240 in high school athletes and 332
in college athletes representing 4.1% of the sample population. Injury rates were calculated
based on total athlete-exposures considering the following equation:
Injury rate per 1000 athlete-exposures = (number of injuries reported/number of exposures) x
1000.

26

The concussion rates were 0.5 concussions per 1000 athlete-exposures for high school
and 0.57 for college, which translates to 3.33 concussions per 1000 high school players per
seasons and 4.1 per 1000 college players per season.
Considering the information collected at the beginning of the season and the two season
data sets, it was observed that among those high school players with a history of concussion 18%
sustained a new concussion, and less than 3% of those with no history sustained one. For the
high school level, the relative risk was calculated by considering 7197 player-seasons and the
number of concussion in the season; the players who had a history of concussion during the
previous five years (296 player-seasons) experienced 53 new cases; the group of players who had
no history of concussions (95.9% of all the player-seasons healthy cases) and sustained one
during the season had 187 cases. Thus, the relative risk was calculated ((53/296)/(187/6901))
indicating that a player that has had a concussion is 6.6 times more likely to sustain another one
in comparison with a player that has not experienced one. At the college level, there were 8107
player-seasons. Six hundred and seventy nine player-seasons had sustained a concussion within
the previous five years. Of the total 332 concussions, 108 were sustained by players with a
history, and 224 were new cases. The relative risk was calculated ((108/679)/(224/7428)),
indicating a risk of 5.3 for those who already had a concussion. When the results from high
school and college were combined, the relative risk was 5.8, still indicating a greater risk for
those players who had sustained a concussion. Based on these findings, the author concluded that
a history of concussion does have an impact on new occurrences but does not seem to have an
impact on the severity of a new concussion. It was inferred that a longer participation in the sport
(particularly if it is a contact sport) will increase the chances of sustaining a concussion.

27

Macciocchi, Barth, Littlefield, and Cantu (2001) studied multiple concussions and
neuropsychological functioning in collegiate football players. The authors indicated that
concussive injuries in American football can cause time-limited neuropsychological and
neurobehavioral problems. They recognized that there is not much evidence of the effects of
multiple concussions. Their study focused on cognitive deficiencies presented after a second
concussion and how they compare with the same measurements after sustaining the first one.
Twenty-four division I-A football athletes from a population of 2300 that participated in a
previous concussive injury study were selected to participate in this study. Players sustaining one
concussion were matched on age, education, years of experience, and prior concussion history
with players sustaining two concussions.

Players in the one concussion group had an average

age of 19.5 years, and a mean of 8.4 years of playing experience, while the two concussions
group had a mean age of 19.1 years and 9.1 years of experience playing football. All participants
were assessed during the preseason to establish baseline data. The Paced Auditory Serial
Addition Task (Gronwall, 1977), the Trail-Making Tests A and B for the Halstead-Reitan
Neuropsychological Test Battery (Retain & Wolfson, 1985), and the Symbol Digit Test (Smith,
1982), in addition to a history questionnaire and a symptom checklist were administered to the
participants. Players who were suspected of sustaining head injuries during practices or games
were examined by athletic trainers and physicians using standardized medical and mental status
procedures. All the cases were consistent with a grade one concussion using the American
Academy of Neurology standards. The results indicated that two grade 1 concussions sustained
at least two weeks apart do not result in more neurocognitive impairment than a single
concussion. Players who sustained 2 concussions performed as well or better on all
neuropsychological tests after their first and second concussions when compared with those that

28

only experienced one concussion. There was no evidence of a decrement in test performance
relative to the performance observed after players’ first concussions. Players who sustained two
concussions performed better on post-season assessments than on preseason examinations.
Among the limitations of the study, the authors recognized the small sample size, the fact that all
of the concussions were grade 1 does not allow any inference related to more severe injuries, and
the timing of the injuries, which in some cases occurred within 12 to 24 months.
Janda, Bir, and Cheney (2002) studied the presence of cumulative concussive effects of
soccer heading in a youth population by quantifying the number of times a player headed the ball
throughout two years either in practices or games. Cognitive function was assessed at the
beginning of the fall and at the end of the spring season (approximately nine months between
measurements). Verbal learning was assessed with the Wide Range of Assessment Memory and
Learning (WRAML) (Western Psychological Services, Los Angeles, CA), attention ability was
assessed using the Wechsler Intelligence Scale for Children – III (WISC-III) (The Psychological
Corporation, San Antonio, TX) tracking and information processing speed was assessed with the
Symbol Digits Modality Test (SDMT), and verbal learning was assessed with a delay test.
Participants also completed a subjective assessment by answering questions at the end of the
spring season about experiencing any symptoms associated to concussions. The age range of the
participants was 10 to 13.7 years of age, with a mean of 11.55. Data from 57 participants (37
males and 20 females) were used for analysis. The average heading in season one was 33.75 and
131.78 headers per female and male players respectively, with a minimum of 1 and a maximum
of 450. Season two had only 1 team participating and was composed by 18 male participants
with a mean age of 13.25 and a range of 12.6 to 14.5 years. The average number of headers in
the second year was 129.6.

29

No significant differences were observed in any of the cognitive function components
tested in the first year. However, results for the second year indicate a marginal significant
difference for verbal learning (p = 0917). These findings support previous research recognizing
negative effects of head impacts on cognitive function. Additionally, they are also in accordance
with previous findings on the inverse relationship between cognitive function decline and
players’ maturation, explained by having experienced more repetitive head trauma as they aged.
Forstl, Haass, Hemmer, Meyer, and Halle (2010) completed a review of acute, subacute,
and chronic neuropsychiatric consequences of boxing. They identify fist speeds of 10 m/s or
greater upon impact, forces of 5000 N (and correlations of this force with weight class), that lead
to translational accelerations of 50 g. Rotational accelerations were also identified as a critical
factor, because they generate shearing forces causing lesions in the upper brainstem.
It was reported that in Olympic and amateur World Championships up to 1984, 13.6% of
the matches had to be stopped due to knockout or other injuries. After introducing the use of
head guards, the percentage was 9.5 (up to 1996), and when the duration of the matches was
reduced from three 3-minute rounds to four 2-minute rounds the percentage was 2.2.
Modifications to the rules, such as the “outclassed rule” reduced the knockouts and other injuries
to zero up to 2004. Boxer’s age and number of matches fought were identified as risk factors for
injuries.
These authors also identified potential risk factors for increased mortality, such as age,
pre-existing brain changes, somatic disease (chronic), medication, dehydration, pronounced
weight loss, large number of punches striking the head during the match, and “second impact
syndrome” with incomplete recovery after a recent injury.

30

Subacute consequences included symptoms present 24 hours after the knockout, such as
headaches, tinnitus, forgetfulness, impaired hearing, dizziness, nausea, and impaired gait.
Cognitive deficit was reported to affect immediate recall, working memory, and reaction time.
Performance in visual-spatial and mathematical exercises was also diminished in those
participating in a study exploring the effects of knockouts even 48 hours after the event. The
authors also reported studies highlighting impaired performance in information processing and
verbal fluency one month after a knockout.
Biochemical changes associated with traumatic brain injury have also been reported in
the literature, particularly identifying the presence of tau, neurofilament light, and glial fibrillary
acidic proteins in higher concentrations as a response to more frequent and harder punches.
Among the chronic consequences, Forstl and colleagues (2010) also found that
professional boxers with longer careers are more susceptible to tremors, dysarthria, Parkinson’s
disease, ataxia, and spasticity. On cognition they experience lower processing, loss of memory,
and dementia. Behaviorally, they suffered more depression, irritability, aggression, criminality,
and addiction.
Rabadi and Jordan’s (2001) review on the cumulative effect of repetitive concussion in
sports, included sports such as soccer, football, ice hockey, and martial arts. They recognized the
prevalence of chronic traumatic brain injury (CTBI) in professional boxing and identified boxing
longer than ten years, participation in over 150 bouts, and retiring after the age of 28 years as
factors for CTBI. The signs and symptoms of CTBI in boxers were more manifest after the age
of 50 and included motor and cognitive impairments as well as behavioral changes. Radiological
imaging has shown structural changes and lesions in the frontal and temporal lobes.

31

CTBI has been associated with soccer, and possible risk factors are increased exposure to
the sport, duration of participation, and increased level of competition. Among the potential
mechanisms of injury were direct forces resulting from collisions with the ground, other players,
or cumulative impacts associated with heading the ball. CTBI in soccer is mostly associated with
a decrease in cognitive function, such as memory, attention, concentration, and judgment.
In football CTBI is associated with repetitive impacts, and a history of concussions.
Neurological impairment manifestations are memory loss, confusion, information processing
speed, attention, and speech difficulties. In ice hockey the incidence of concussions increased
with the level of play through the professional level. Additionally, it was reported that using
protective equipment may help to mitigate the occurrences of concussions. In martial arts
information on CTBI is limited. However case studies have identified cerebella ataxia, seizures,
and dementia, associating these to repeated blows to the head. Recommended preventive
measures include “reducing the exposure of high-risk athletes using protective equipment,
enforcing strict rule adherence, training and supervising athletes, and increasing medical
surveillance”.
Pellman, Viano, Tucker, Casson, and Waeckerle (2003) reproduced game impacts and
injuries that produced concussions in professional football. The authors pointed out the start of
the National Operating Committee on Standards for Athletic Equipment (NOCSAE) in 1973 to
establish standards for the impact performance of football helmets, limiting the Severity Index
(SI), which was based on resultant head acceleration. Adoption of these standards by the helmet
manufacturers by 1980 showed “significant reductions” in injuries observed in youth football
(i.e., a 51% reduction in fatal head injuries, 35% reduction in concussions, and 65% reduction in
cranial fractures). In spite of rule changes implemented later, the reduction of injuries was still

32

considered to be associated to helmet design improvement, and was explained by the increase of
neck injury rates, which is indicative of the occurrence of head impacts.
Hodgson and Thomas (1985) reported an average SI of 1064 for helmets meeting
NOCSAE standards. It is recognized that improvements continue to be made on helmet
performance, and the attention was focusing on the incidence of concussion in sports. The
summative effect of multiple concussions and their long term effects were also noted.
It was reported that in 1994 the NFL formed a committee to study mild traumatic brain
injuries (MTBI) in football (Pellman, 2003), with the mission to scientifically investigate
MTBI’s in the NFL. Thus, MTBI cases in professional football were systematically recorded
between 1996 and 2001, generating approximately 90 MTBI cases that were studied by
evaluating video tapes of events when a MTBI was suspected. MTBI were reported by a
physician and a trainer, as well as the engineering group responsible of analyzing and
reconstructing the game impacts. Reconstructions were made using videotapes of the games.
Location of the impact and the striking objects were identified. These reconstructions determined
impact velocities, orientations, and helmet kinematics. These variables were later used in the
laboratory to replicate the impacts. The lab reconstructions involved the use of a Hybrid II male
anthropometric test device (crash test dummy) with a football helmet strapped to it. A
mechanical device impacted the helmet at various velocities and angles. Velocities and
accelerations were measured 3-dimensionally at the center of gravity of the head. Nine
accelerometers were placed to record linear and rotational acceleration. Two high speed cameras
recorded head kinematics in the lab. The authors identified two categories of potential errors in
their measurements: position of the accelerometers and data-processing techniques to determine
accelerations and use of broadcast video as the bases to determine collisions. They reported that

33

translational acceleration of the head’s center of gravity was determined from three orthogonal
2
accelerations measured in the dummy, and was expressed in g’s (1g = 9.8 m/s ). The use of

Lissner, Lebow, and Evans (1960) Concussion Tolerance Curve was cited to estimate the
tolerable peak translational acceleration of the head. Various works were cited providing a range
between 42 to 80 g’s as the limits of tolerance in humans.
The Severity Index (SI) was calculated by using Gadd’s (1966) method:
T

SI = ∫ a(t ) 2.5 dt
0

where,
a(t) = the resultant translational acceleration at the head center of gravity and
T = duration of the acceleration pulse.
SI cannot exceed 1200 to be acceptable.
The Head Injury Criterion (HIC) used by the National Highway Traffic Safety
Administration considers a SI variation, and was reported as:
t2

HIC = {(t 2 − t1 )[ ∫ a(t )dt /(t 2 − t1 )]2.5 } max
t1

where,
a(t) = resultant translational acceleration at the head center of gravity and

t 2 − t 1 = T = 15 ms (used to determine maximal value).
The analyses included 174 cases with 29% of the impacts on the facemask, and the
remaining on the helmet shell. There were 25 concussions, 16 on the offense, five on the defense,
and the rest on special teams. Thirty one videos were analyzed which included those where

34

concussions were reported. The peak head acceleration for concussed players averaged 98 ± 28
g, with 15 ms duration, and was significantly greater than the 60 ± 24 g experienced for
uninjured players. Concussion was primarily related to translational head acceleration resulting
from helmet impact to the face mask at an oblique or lateral angle, and falling hitting the back of
the head. Concussion was strongly correlated with SI, HIC, peak translational acceleration, and
head velocity change. Nominal tolerance levels for concussion were SI of 300 and HIC of 250
for helmet impacts. There was a low correlation with rotational acceleration.
Hodgson’s (1990) study tested several types of helmets using a child size humanoid
headform (6 5/8” in diameter), and provided evidence of the effectiveness of the use of helmets
in reducing head injuries. A small size humanoid head was instrumented with a triaxial
accelerometer to measure the linear acceleration experienced at the center of gravity of the head.
These values were used to calculate the Severity Index (SI). Drop tests were conducted from the
following heights: 1, 1.5, and 2m.
2

T

( SI ) = ∫ Adt
o

where, T is the effective impact duration, A is the instantaneous acceleration (g), and dt is time
increment of integration.
The risk of injury was evaluated according to the Severity Index and use of a risk chart,
which was constructed from the data obtained from experiments of head impacts received by
adult cadavers in controlled falls. The author recognized that the values of the chart may be
affected negatively by age of the subjects, and also by the rotational motion at impact that may
lower the impact tolerance of an individual. The overall results indicated a decrease of
acceleration associated with the use of helmets. While falling from 1 m without head protection

35

may result in a serious head injury in 70-99 % of the population, the use of helmets reduced this
to 1 %. When the height was increased to 2 m, the risk varied from 6-35% depending on the type
of helmet. Caution must be exerted when using this data, because it was observed that there were
differences on the protective behaviors of the helmets if the forces were not uniform and helmets
could not be kept in place. When the results were analyzed to evaluate the stress in the neck,
there was a difference between shell and no-shell helmets, where the later produced greater neck
flexion, axial loading, and head angular acceleration. Neither helmet was able to prevent injuries
to the facial region.
Dau, Chien, Sherman, and Bir (2006) studied the effectiveness of boxing headgear for
limiting injury. In their research they used a Hybrid III dummy. There were 27 amateur boxers
who participated in the study. They were asked to punch the dummy’s head. The variables
measured were linear and angular accelerations of the head, head injury criteria (HIC), and
punch force. The Hybrid III head had nine linear and three angular accelerometers, the neck had
six-axis load cells, and the boxers’ gloves had three accelerometers. Sampling rate was 20 KHz.
The dummy head, with and without headgear, was struck.
A decrease of all variables with the headgear in place, was reported. Peak rotational
2
acceleration decreased from 9164.1 to 5534.78 rad/s with the use of the headgear, punch force

also decreased from 4260.51 to 2815.59 N, the HIC decreased from 79.23 to 47.34, and the peak
resultant acceleration fell from 78.04 to 51.79 g. Punch velocity was also reduced from 9.57 to
8.43 m/s.
In King’s (2000) review on the fundamentals of impact biomechanics, the author
identified two injury mechanisms for the brain, and pointed out that diffuse axonal injury can be
produced by angular or linear acceleration, because both can generate shear stress in the brain.

36

However, he also cautioned that in spite of a body of knowledge related to linear and angular
accelerations as injury mechanisms, there was not enough evidence to support the idea of shear
stress. When head injury mechanisms were explained with more detail, the author listed them as
“positive pressure, negative pressure, and shear due to pressure gradients or relative motion of
the brain with respect to the skull”(p.58), suggesting that movement of the brain after impact has
a direct effect on the cellular structure, particularly on the axons, which respond with swelling.
This particular observation provided some evidence that diffuse axonal injury (DAI), which
takes several hours to develop, was a result of the impact and not secondary to ischemia or
increased intracranial pressure, as it has been suggested by other authors. He also indicated that
most of the testing done in the car industry to evaluate injury risk from impact in humans is
based on a criteria that defines “reasonably safe” levels, as meaning that injuries sustained by a
car occupant should not be life-threatening. Along with this criteria, others have also been
develop, among these, the Abbreviated Injury Scale (AIS), developed by emergency room
physicians (Committee on Medical Aspects of Automotive Safety, 1971), where severity is
defined as a “threat to life and is not based on disability or impairment”(p.57). In this scale, a
life-threatening injury will receive a value of four. In spite of these efforts, there is still a void on
how to express in quantitative terms the agent(s) that cause these injuries. (Table 1).

37

Table 1
Abbreviated Injury Scale (AIS)
AIS
Severity
0
No injury
1
Minor
2
Moderate
3
Serious
4
Severe
5
Life threatening
6
Maximum
9
Unknown
Note. Adapted from “Fundamentals of impact biomechanics: Part I – Biomechanics of the head,
neck and thorax” by A.I. King, 2000, Annual Review of Biomedical Engineering, Copyright 2000
by Annual Reviews.
On head injury tolerance, the author recognized that several models have been used, and
identified the Gadd Severity Index (GSI) (Gadd, 1966) as the one with confirmed validity (tested
on subhuman primates) and built upon the contributions of the previous indexes. This index
considers the acceleration of the head center of mass (a(t)), time (t), and the duration of the
impact pulse(T).
T

GSI = ∫ a (t ) 2.5 dt ≤ 1000
o

The GSI has been re-named the Head Injury Criterion (HIC), and redefined to be
considered the current standard for the US federal government for automotive and other safety
legislation. It is defined as follows:

T 2

HIC =  ∫ a (t )dt 
 T1




2.5

/(T 2 − T 1) ≤ 1000

It is important to note that this criterion is valid for linear acceleration impacts only; does
not consider angular accelerations, even though they are present during impacts, but no criterion
is available for angular accelerations.

38

King, Yang, Zhang, and Hardy (2003) explored the causal relationship between head
injury and linear and angular acceleration. The authors indicated that based on the automotive
industry data on injuries, there were approximately 1.5 million traumatic brain injuries per year
in the US, and 2% of the US population lives with disabilities resulting from a traumatic brain
injury. The current literature indicates that the principal cause of injury is brain deformation or
strain during head impacts. However, it is not possible to measure this variable in vivo. Thus,
head acceleration is used as an alternate parameter. These authors recognized linear and angular
accelerations as the two major mechanisms of head injury. Rotational acceleration was thought
to produce focal and diffuse brain injuries, while linear acceleration was associated with focal
brain injuries.
King et al. (2003) listed various injury mechanisms that have been proposed to explain
concussion mechanisms, among them were the shear strains generated by rotation and cited in
Holbourn’s (1943) work; extent of relative displacement due to impact from different directions,
supported by Pudenz and Sheldon’s (1946) work; and the coup/countercoup cavitation associated
with the relative displacement between the brain and the skull, reported by Gross in (1958).
Other mechanisms include the shear stress, distortion or mass movement in the brain stem
resulting from impact loading, and its linear acceleration, as presented by Gurdjian, Webster, and
Lissner (1955); Gurdjian, Lissner, and Evans (1961); Gurdjian, Lissner, and Patrick (1963); and
Hodgson, Thomas, and Gurdjian (1969); the pressure waves traveling through the brain proposed
by Goldsmith (1972); strains affecting the brain in a centripetal sequence, as described by
Ommaya and Gennarelli (1974); and the impact pulses containing frequencies that are close to
the nodal frequencies of the skull/brain which are capable of producing injury due to resonance,
a theory proposed by Willinger, Taleb, and Kopp (1996). The authors also cited the results of

39

Hardy, Foster, Mason, Yang, King, and Tashman (2001) where relative motion data between
brain and skull were studied using cadaver heads. Linear acceleration peak was in excess of 60 g
2
and the angular acceleration was above 200 rad/s . Additional tests were carried out at linear
2
accelerations in excess of 200 g and 10000 rad/s . It was reported that linear acceleration created

a 1mm displacement of the brain at most, while angular acceleration produced displacements of
5mm regardless of the direction of impact.
After reviewing studies on helmets that indicated a reduction on linear acceleration in all
the helmet models tested, and in some cases showed an increase of the angular component, King
et al. (2003) concluded that because the results support the idea that the helmet reduces the
occurrence of concussions, and that there was a reduction in the linear component, even though
the rotational component may have even increased, then there may not be a link between
concussions and the angular component.
In a more recent study by Zhang, Dwarampudi, Yang, and King (2003), also cited by the
authors, and conducted in 2001 on NFL players, showed that an average linear acceleration of
94±27 g was known to cause a concussion, as well as angular accelerations of 6398 ±1978
2
rad/s . These accelerations produced a strain over 10% in the midbrain, upper brain stem, and

most of the diencephalon, in addition to the frontal lobe. This rate of strain was hypothesized to
be the key biomechanical parameter to explain the cause of brain injury and concussion.
The guidelines for rating injury measures, developed by the Insurance Institute for
Highway Safety (2009) were created to provide uniform criteria for rating injuries. The data
th
were “obtained from an instrumented 50 percentile male Hybrid III dummy seated in the driver

40

seat” (p.2). Twenty eight measures were recorded from the following body regions: head and
neck, chest, left leg and foot, and right leg and foot. Four injury parameters were used to evaluate
protection for the head and neck. The injury protection ratings went from good, to acceptable, to
marginal or poor based on the injury parameters. The rating criteria indicated that the whole
region would receive the same rating as the lowest of the parameters of that particular region.
Thus, if any body parameter had a poor result, then the whole region was to receive a poor
rating. The authors emphasized that the data presented are guidelines that in no way include all
the possible circumstances that may be present in any particular event. Thus, caution must be
exercised. When evaluating the risk of injury in the head, a 5 percent risk of a severe injury is
estimated to be a HIC-15 (Head Injury Criteria evaluated over a period of 15 ms) of 700,
equivalent to a score of 4+ on the Abbreviated Injury Scale (AIS). When these values are
considered as multiples of acceleration, a value of 70 g is critical, because depending on the
timing of this value with respect to the HIC-15, the injury projection rating can be given a lower
evaluation (higher risk of injury). A range of accelerations of 15-90 g experienced by a Hybrid
III dummy head results in forces that represent 670 to 4000 N, which are enough to cause face
and skull fractures. Aside from the evaluation of the head, the neck was also evaluated, but
mostly on the tension experienced axially and the bending moment about a lateral axis passing
through the dummy’s occipital condyle. These values have been reported to be 6806 N for the
neck axial force during tension/flexion, and 6160 N under compression/extension conditions.
Similarly, the bending moments have been observed to be 310 to 135 Nm, respectively.
Definitions of Injuries in Martial Arts

The definition of injury is difficult due to the differences in perspective and criteria as to
what is considered an injury and how severe it is. The perspective from an epidemiologist is

41

quite different from that of a physician or an engineer. To exemplify these differences, several
definitions are presented.
Birrer and Halbrook (1988) based their definition on medical judgment of expected
physical impact as well as life threat and potential for permanent impairment; thus, all non fatal
injuries were classified on a six point scale with injury classifications ranging from minor to
most severe. Scale values increased by 1 point if the patient was admitted for inpatient hospital
care.
Hung (1997) defined a sports injury as one suffered from being engaged in sports
activities. He also indicated that participation in a sport placed persons at risk for incurring sports
related injuries. However, there was no mention on severity, but Hung recognized that the
occurrence and frequency of an injury can impair performance, lead to lost competitiveness,
disability, and, in some severe cases, even death.
Van Mechelen, Hlobil, and Kemper (1992) define a sport injury as any injury occurring
as a result of sports activity and causing one or more of the following: the subject had to stop
sports activity and/or could not fully participate in the next planned sports activity, and/or could
not go to work the next day, and/or needed medical attention. In addition, a fifth characteristic
defined an overuse injury as suffering from pain or stiffness during ten subsequent days while
doing sports.
Pieter (1991) defined serious injuries as those that lead to time-loss from participation of
one day or more; furthermore, Pieter and Zemper (1998) consider an injury as any circumstance
for which assistance was sought from medical personnel.

42

Injury Mechanisms in Martial Arts

There are many factors that contribute to injuries in martial arts. Kannus, Niittymaki, and
Jarvinen (1988) indicated that overuse in systematically trained children and adolescents tends to
increase epiphyseal injuries and avulsion fractures, acute characteristic injuries, and long bone
fractures. Abrasion, laceration, dislocation, contusion, and fracture are common terms to injuries
that have their origin in sports (see definitions section). When studying these factors in
competition, the following has been observed:
Table 2 identifies the distribution of injuries by mechanism per 1000 Athlete-Exposures
(A-E) of two different round robin tournaments - one restricted for adults and the other
exclusively for adolescents (Pieter, Van Ryssegem, Lufting, & Heijmans, 1995) and (Pieter &
Zemper, 1997a).

43

Table 2
Injury Mechanisms per 1000 Athlete-Exposures (A-E)
A-E men = 258 and women = 114
Pieter et al. 1995
Men
Women
N=67
N=30
Injury
Injury
Injury Mechanism
No.
No.
Rate
Rate
Delivering round kick
12
46.51
2
17.54
Receiving round kick
11
42.64
4
35.09
Receiving punch
3
11.63
Receiving spinning back
3
11.63
4
35.09
kick
Delivering punch
2
7.75
Receiving spinning hook
1
3.88
kick
Receiving axe kick
1
3.88
Simultaneously round kicks
1
3.88
1
8.77
No evidence of contact
1
3.88
Receiving a blow
Delivering a blow
Impact with surface
Simultaneous blows
Overuse/gradual onset
Other
Total
36
139.54
11
96.49

44

A-E boys = 6068 and girls = 1538
Pieter & Zemper, 1997a
Boys
Girls
N= 3341
N= 917
Injury
Injury
No.
No.
Rate
Rate

2
212
90
21
9
5
16
354

.33
34.77
14.83
3.46
1.48
.82
2.64
58.34

2
46
17
9
4
2
7
87

1.3
29.91
11.05
5.85
2.6
1.3
4.55
56.57

The number and mechanisms of injuries severe enough to require the player to
retire from the competition and miss at least one practice session after the injury are
illustrated in Table 3. The injury mechanism of concussions in taekwondo events are
illustrated in Table 4.
Table 3
Injury mechanism of time-loss injuries per
1995)
Men
Injury Mechanism Number Injury
Rate
Receiving round
3
11.63
kick
Receiving punch
1
3.88
1
3.88
Receiving
spinning hook
kick
Delivering round
1
3.88
kick
No evidence of
1
3.88
contact
Total
7
27.13

1000 Athlete-Exposures (A-E) (Pieter et al.
Women
Injury Mechanism

Number

Receiving spinning
back kick

1

Injury
Rate
8.77

Total

1

8.77

Table 4
Injury mechanism of cerebral concussions per 1000 Athlete-Exposures (A-E)
Study by
Study by
Study by
Study by
Pieter &
Pieter &
Pieter et al.,
Men
Pieter et al.,
Zemper,
Women
Zemper,
1995
1995
1998
1998
Injury
Mechanism

No.

Receiving
round kick

3

Receiving
punch
Receiving a
blow
Impact with
surface
Total

1

Injury
Injury Injury
No.
Rate
Rate Mechanism
Receiving
11.63
spinning
back kick

1

Injury
Injury
No.
Rate
Rate
8.77

3.88
22

15.50

6.46

2
4

No.

.59

24

4

7.04

Total

45

1

8.77

2.42

4

2.42

CHAPTER III
Methods
Participants

Participants were recruited from two gymnasia in the Detroit, Michigan area after
making arrangements in advance with the instructors at each site. Site A was made
available by the Grand Master exclusively for the research data collection session. He
invited all students interested in participating in the project to come to the gymnasia on a
set date. A data collection session was also hosted at Site B on a date during which
classes were being taught. Students interested in participating were allowed to step out of
class to have their data collected. The research was approved by the Michigan State
University Institutional Review Board (IRB) and the Wayne State University Human
Investigation Committee (HIC). Verbal assent (see Appendix C) was obtained from each
participant younger than 13 years of age and written assent (see Appendix D) was
obtained from those participants older than 13 years of age. Written assent (see
Appendices A and B) was obtained from one parent of each youth who assented to
participate. A questionnaire was administered to collect demographic data (Appendix E).
Anthropometric data were collected using a data sheet (Appendix F).
There were 18 participants (three female and fifteen male) with a mean age of
10.7 (1.7) years (range 7-14 years of age). Only one male participant reported left foot
predominance. Participants were categorized into three age groups, where pre-pubescent
participants were included in the youngest age group (under 9 years); the second group
(10-13 years) was set considering the possibility that children in this age range may
experience the initiation of the adolescent growth spurt during this time. The final group

46

(older than 14) was set considering that by this age most of the participants would have
reached adolescence. Additionally, these age groups are commonly used to set up
competition categories in martial arts events. (Table 5).

47

Table 5
Age Groups and Number of Kicks
n
Participant
Age (yrs.) Age Group (yrs.)
ID #
4

12

2

M1
M2
M3
M4
M5
M6
M7
M8
M9
F1
F2
M10
M11
F3
M12
M13
M14
M15

7
9
9
9
10
10
10
10
10
11
11
11
11
12
12
12
14
14

Under 9

10 to 13

14 and older

Gender

Skill Level

Height
(m)

male
male
male
male
male
male
male
male
male
female
female
male
male
female
male
male
male
male

beginner
advanced
beginner
beginner
beginner
beginner
beginner
beginner
advanced
beginner
beginner
beginner
advanced
beginner
beginner
beginner
beginner
advanced

1.23
1.35
1.39
1.40
1.46
1.54
1.48
1.42
1.49
1.31
1.32
1.51
1.59
1.53
1.46
1.54
1.62
1.7

48

Weight
(kg)
27.0
44.5
37.8
43.0
59.1
86.6
38.9
37.8
60.6
29.2
29.2
57.4
48.6
57.2
49.8
49.5
50.5
59.6

Body mass
index
2
(kg/ m )
17.8
24.2
19.4
21.7
27.4
36.4
17.6
18.7
27.3
16.8
16.7
24.8
19.1
24.1
23.2
20.7
19.2
20.6

# of
Kicks
9
11
11
11
12
7
4
8
10
10
10
5
12
10
10
14
10
7

Participants’ experience in martial arts ranged from 1 to 96 months of practice
with a mean of 26 months (Figure 1). Fourteen participants were classified as beginners
(colored belts) and four males (M2, M9, M11, and M15) as advanced (black belts)
(Figure 1). Most of the participants (n=15, 83%) expressed an interest in full-contact
sparring competition, and more than 60% in forms competition (n=11). Ten participants
(55%) reported to participate in one or more sports in addition to their martial art.

*
*

*

*

Figure 1. Experience of participants by age and gender (* indicates a black belt
participant).
Procedures
Instrumentation and Setup
th
A 5 percentile Hybrid III female dummy head was mounted on a support base

(Figure 2). This head size (3.7 kg, 0.53 m in diameter) was used due to its similarities to
the participants’ anthropometric characteristics. The support base was stabilized with 100
pounds of sand to prevent excessive movement, thus reducing the risk of injuries.

49

Martial arts
headgear
Hybrid III
female dummy
head

Support
base

Stabilizing sand bags
Figure 2. Testing setup.
The coordinate system established for the head followed SAE J211-1
recommendations (Society of Automotive Engineers, 1995) resulting in +X toward the
front of the head in an anterior-posterior axis, +Y to the right of the head in a mediolateral axis, and +Z toward the neck in the longitudinal (vertical) axis (Figure 3).

50

medial-lateral axis

anteriorposterior axis
longitudinal axis
Figure 3. Orientation of standardized dummy coordinate system. For interpretation of the
references to color in this and all other figures, the reader is referred to the electronic
version of this dissertation.
A 3/4 inch thick vinyl covered foam, medium size, protective martial arts
headgear (Proforce Lightning, Proforce Inc., USA) was placed on the dummy head to
reduce the exposure to its hard surface by the feet in kicking, thus minimizing the risk of
injuries (Figure 4).

Figure 4. Headgear.
All participants wore 5/8 inch dipped foam foot pads by Century (Century LLC.
Oklahoma City, OK, USA) provided by the research team during their trials as an
additional measure to reduce the risk of injury (Figure 5). Each participant selected the
size of foot pad that he/she felt most comfortable using.

51

Figure 5. Foot pad used by participants to reduce the risk of injury during testing.
For each participant, the dummy head was adjusted to the same height as the head
of each participant during his/her stance (Figure 6).
Hybrid III
female
dummy head

Headgear

Support
base

Foot
pad

Figure 6. Dummy head set at participant’s stance head height.
Three 2000 g’s accelerometers (Endevco 7264, ENDEVCO Corp. San Juan
Capistrano, CA, USA) were placed in the mounting plate in the Hybrid III female dummy
head perpendicular to each other following manufacturer’s recommendations (Figure 7).
These devices are lightweight (1 gr) piezoresistive accelerometers designed for

52

applications requiring minimal mass loading and meet SAEJ2570 (Society of Automotive
Engineers, 2009) specifications for anthromorphic testing. Three angular rate sensors
(DTS ARS-12K, Diversified Technical Systems, Inc. Seal Beach, CA, USA) were also
placed in the mounting plate (Figure 7). These devices are designed for high rate dummy
impact and vehicle component testing for precise measurements of head rotation and
other biodynamic measurements. They weigh less than 3 gr, have a SAE class 100
response and a range of ±12000 degrees/sec.

Accelerometers

Angular
sensors

Figure 7. Accelerometers and angular sensors mount.
A TDAS PRO Sensor Input Module (SIM) (Diversified Technical Systems Inc.
Seal Beach, CA, USA) data system was used to collect data from the accelerometers and
angular sensors. This system has eight fully-programmable sensor input channels with
isolated excitation that can integrate various modules (Figure 8) to increase its data

53

collection capability. The system is controlled by its TDAS Control software which
allows automatic sensor assignment, detailed channel diagnostics, and real-time data
display (Figure 9). TDAS PRO functions were set-up using an IBM-compatible
computer. Data were stored in each module and, after testing was complete, it was
downloaded to the PC hard drive in binary format. Once on the hard drive, the binary
data files were then unpacked for viewing and post-processing. It is certified to NHTSA,
FAA, ISO 6487 and SAE J211 (Society of Automotive Engineers, 1995) data acquisition
practices. Sampling was done at 10 KHz for each channel, and recorded for 30 seconds to
allow participants to complete ten or more kick trials during this period of time. The data
were filtered with a CFC1000 filter (-3dB point of 1650 Hz) as specified by SAE J211
standard for head accelerometers.

Figure 8. TDAS PRO modules.

54

Figure 9. TDAS software screen snapshot.
Each participant was asked to consecutively kick the side of the dummy head with a
roundhouse kick five times with one foot as hard as possible and then to repeat the
process with the opposite foot within a 30 second period. Participants were asked to
assume a right ready stance (staggered foot position with right foot farthest from the
target) and, at an indication by a member of the research team, to kick the head assuming
a ready stance before each kick. Once these trials were completed, the participant
switched to the opposite stance and began kicking with the left foot until the completion
of the five additional trials (Figure 10), again, assuming a ready stance before each kick.
If there were collection time left after the ten trials, the participant was asked to continue
kicking with his/her preferred foot until the collection time expired. Allowing continued
kicking resulted in a total of 171 attempts available for analysis.

55

Figure 10. Participant roundhouse kick trial.
Anthropometric Measurements

A SECA portable digital scale (SECA model Alpha 770, Hamburg, Germany)
was used to measure weight in kilograms to the closest 0.1 kilogram. Participants wore
their martial arts uniform while being weighed and were barefoot. A

SECA

portable

stadiometer (SECA model 214, Hamburg, Germany) was used to measure standing,
sitting, and shoulder heights to the closest 0.1 centimeter. Participants were barefoot.
A GPM 101 anthropometer (Siber & Hegner, Zurich, Switzerland) was used to
measure biacromial and bicristal widths to the closest 0.1 centimeter. Participants wore
their martial arts uniform during measurements, and were barefoot. A Sit and Reach Flex
Tester (Power-Systems, Inc. Knoxville, TN, USA) was used to measure flexibility of the
shoulder joints and shoulder girdle, and lower back and hip regions to the closest 0.5
centimeter.

56

CHAPTER IV
Results and Statistical Analysis
Anthropometry

These data were collected to provide descriptive information on participants’
anthropomorphic characteristics and explore their effect on linear and angular
accelerations. There are differences by age and gender in height, weight, flexibility,
biacromial and bicristal widths, thus, these measurements provided an understanding of
the effects of maturation on linear and angular accelerations. Table 6 shows
anthropometric data and flexibility scores. Participants’ mean standing height was 146.7
centimeters (range from 123 to 170 centimeters) and mean weight was 48.15 kilograms
(range from 27.0 to 86.6 kilograms). Mean Body Mass Index (BMI) was 22.0 kg/ m

2

2
(range from 16.8 to 36.4 kg/ m ). Sit and reach flexibility ranged from -7.5 to 14

centimeters, with a mean of -0.1cm.
When examined by gender, mean standing heights were 139.2 cm for females and
148.21 cm for males (Figure 11). Mean weight was 38.55 kg for females and 50.07 kg for
males (Figure 12). Mean flexibility for the sit and reach test was 6.5 cm for females and 2
2
1.2 cm for males (Figure 13). Mean BMI was 19.2 kg/ m for females and 22.6 kg/ m for

males (Figure 14).

57

Table 6
Sample Anthropometric Data and Flexibility Scores
Mean
Age (yrs.)
Height (cm)
Weight (kg)
Sit and Reach (cm)
2
Body Mass Index (kg/ m )

SD

Min

Max

10.7
146.7
48.1
-.1
22.0

1.7
11.8
14.5
6.1
4.9

7
123
27
-7.5
16.78

14
170
86.65
14
36.44

Figure 11. Participants’ height by age and gender.

58

Figure 12. Participants’ weight by age and gender.

Figure 13. Participants’ sit and reach flexibility by age and gender.

59

Figure 14. Participants’ body mass index by age and gender.
The overall mean of the sitting height to standing height ratio was 0.51 with a
range from 0.48 to 0.53 (Figure 15). Biacromial to bicristal ratio ranged from 0.8 to 1.4
with an overall mean of 1.2 (Figure 16). Grouped by gender, mean sitting height to
Standing height ratio was 0.51 for both groups. Mean Biacromial to Bicristal ratio was
1.27 for females and 1.23 for males. When participants were grouped by skill level,
Sitting height to Standing height ratio mean for each groups was 0.5 (Figure 17). The
Mean Biacromial to Bicristal ratio for beginners was 1.26 and 1.13 for advanced
participants (Figure 18). Mean BMI for beginners was 21.8 and 22.8 for advanced
participants (Figure 19).

60

Figure 15. Participants’ sitting height to standing height ratio by age and gender.

Figure 16. Participants’ biacromial to bicristal ratio by age and gender.

61

Figure 17. Participants’ sitting height to standing height ratio by skill level.

Figure 18. Participants’ biacromial to bicristal ratio by skill level.

62

Figure 19. Participants’ Body Mass Index by skill level.

Performance Data

Table 7 shows the number of successful data collection trials (number of
roundhouse kicks to the head recorded) from each participant and the corresponding
averages per participant for Mean Linear Acceleration (MeanMaxLinAcc), Mean
Angular Acceleration (MeanMaxAngAcc), Mean Gadd Severity Index (SI), which
according to Pellman, Viano, Tucker, Casson, and Waeckerle (2003) is calculated by
integrating the resultant translational acceleration at the head center of gravity over the
duration of the acceleration pulse and cannot exceed 1200 to be acceptable, thus
indicating a football helmet’s ability to absorb forces, and protect its user, and the Mean
Head Injury Criteria (HIC) (considered as a SI variation used by the National Highway
Traffic Safety Administration, and reported by Pellman et al. (2003). Figure 20 compares
linear acceleration values from all trials by participants to low and high thresholds known

63

to cause concussions. Figure 21 shows minimum, maximum and means of linear
accelerations generated by each participant. Figure 22 compares angular acceleration
values from all trials by participants to thresholds known to cause concussions. Figure 23
shows minimum, maximum and means of angular accelerations generated by each
participant.

64

Table 7
Mean Values for Linear and Angular Accelerations, HIC, and SI by Participant
Age
11
11
12
7
9
9
9
10
10
10
10
10
11
11
12
12
14
14

Gender
female
female
female
male
male
male
male
male
male
male
male
male
male
male
male
male
male
male

Skill level Participant ID # Kicks MeanMaxLinAcc (g)
beginner
F1
10
2.73
beginner
F2
10
5.29
beginner
F3
10
83.76
beginner
M1
9
8.88
advanced
M2
11
11.83
beginner
M3
11
15.26
beginner
M4
11
10.44
beginner
M5
12
7.15
beginner
M6
7
16.59
beginner
M7
4
22.26
beginner
M8
8
35.08
advanced
M9
10
26.71
beginner
M10
5
19.23
advanced
M11
12
25.03
beginner
M12
10
9.42
beginner
M13
14
14.61
beginner
M14
10
15.5
advanced
M15
7
41.45

65

MeanMaxAngAcc
2
(rad/sec )
Mean SI
357.8
0.24
554.4
1.78
3181.7
127.85
1585.7
2.12
2089.4
4.83
1247.6
9.16
895.8
2.86
1454.8
2.11
1210.3
8.43
2161.8
16.62
3426.3
28.34
1262.2
21.22
1143.1
16.26
4230.7
17.98
907.9
3.77
1025.2
6.88
3203.9
13.26
4154
57.36

Mean
HIC
0.13
0.61
102.42
1.17
2.67
6.12
2.14
0.76
6.22
12.06
21.72
14.36
12.95
8.43
2.78
4.31
5.84
47.1

Figure 20. Linear acceleration values per trial by participant, low and high thresholds from Pellman et al. (2003).

66

Figure 21. Mean, minimum and maximum linear acceleration values by participant.

67

Figure 22. Angular acceleration values per trial by participant. Low threshold from King et al., (2003), high threshold from Zhang,
Dwarampudi, Yang, and King (2003).

68

Figure 23. Mean, minimum and maximum angular acceleration values by participant. Low threshold from King et al., (2003), high
threshold from Zhang, Dwarampudi, Yang, and King (2003).

69

Female F1 was 11 years old and had practiced for 3 months, F2 was 11 years old
and had practiced for 2 months; F3 was 12 years old and had practiced for 24 months.
Table 8 provides overall and by gender descriptive data of linear and angular
accelerations, HIC, SI and number of kicks. Descriptive data of linear and angular
accelerations, HIC and SIC by skill level are found in Table 9. Pellman, Viano, Tucker,
Casson, and Waeckerle (2003) reported nominal tolerance levels for concussion of 300
for SI and 250 for HIC, observed in helmet impacts. These authors also reported linear
accelerations between 42 to 80 g’s as the limits of tolerance in humans.

70

Table 8
Descriptive Statistics for Linear and Angular Acceleration, HIC and SI Overall and by Gender
AngAcc
LinAcc
2
(rad/s )
Gender
(g’s)
1753.82
29.39
Female
Mean
(SD 29.56)
(SD 1374.23)
(n=25 roundhouse kicks) Minimum - Maximum
2.73-84.81
357.80-3991.90
1603.09
19.21
(SD 1145.38)
Male
Mean
(SD 15.86)
(n=146 roundhouse kicks) Minimum - Maximum
1.66-86.72
274.50-6109.20
1625.12
20.70
(SD 1178.31)
Overall
Mean
(SD 18.73)
1.66-86.72
274.50-6109.20
(n=171 roundhouse kicks) Minimum - Maximum
Table 9
Descriptive Statistics for Linear and Angular Acceleration, HIC and SI by Skill Level
MaxAngAcc
MaxLinAcc
2
(rad/s )
Skill Level
(g’s)
1463.94
19.02
Beginner
(SD 1038.55)
Mean
(SD 18.16)
(n=131 roundhouse
Minimum kicks)
Maximum
1.66-84.81
311.10-4472.20
2153.02
26.21
Advanced
Mean
(SD 19.77)
(SD 1443.52)
(n=40 roundhouse
Minimumkicks)
Maximum
2.38-86.72
274.50-6109.20

71

HIC
30.47
(SD 41.06)
0.13-141.17
12.94
(SD 23.02)
0.03-177.00
15.50
(SD 26.99)
.03-177.00

HIC

SI
39.87
(SD 53.34)
0.24-183.13
17.26
(SD 28.49)
0.06-219.88
20.56
(SD 34.02)
.06-219.88

SI

12.96
(SD 22.77)

17.51
(SD 29.25)

141.17
23.81
(SD 36.80)

183.13
30.58
(SD 45.40)

0.09-177.00

0.35-219.88

Tests of Null Hypotheses

Correlational analyses were performed for age, months of practice, standing
height, weight, flexibility, BMI, Linear Acceleration (LinAcc), Angular Acceleration
(AngAcc), Severity Index (SI), and Head Injury Criteria (HIC). Results of the
correlational analyses for 171 kick trials were presented in Tables 10 and 11.
Table 10
Sample Pearson Correlation Coefficients (2-Tailed) Among Performance Parameters
and Injury Factors (n=171 roundhouse kicks)
Linear Acceleration Angular Acceleration of Severity Head Injury
of Hybrid III
Hybrid III Dummy Head
Index
Criteria
Dummy Head
(SI)
(HIC)
(AngAcc)
(LinAcc)
LinAcc

.714**

SI

.930**

.705**

AngAcc

.932**

.697**
.998**

HIC
** Indicates significance at the 0.01 level.
Table 11
Sample Pearson Correlation Coefficients (2-Tailed) for Mean Values, Among Age,
Experience, Anthropometry, Performance Parameters, and Injury Factors (n=171
roundhouse kicks)
Sit and Reach
BMI
Age
Months of Standing
Weight
Flexibility
Practice
Height
.293**
.232**
.282**
.349**
.078
.307**
LinAcc
2
2
2
2
2
2
(r = .01)
(r = .09) (r = .08) (r = .12) (r = .05) (r = .07)
.389**
.376**
.434**
.249**
.281**
.052
AngAcc
2
2
2
2
2
2
(r = .15) (r = .14) (r = .18) (r = .06) (r = .07)
(r = .00)
.314**
.376**
.225**
.264**
.041
.360**
SI
2
2
2
2
2
2
(r = .00)
(r = .12) (r = .09) (r = .14) (r = .05) (r = .06)
.354**
.319**
.369**
.219**
.258**
.038
HIC
2
2
2
2
2
2
(r = .12) (r = .10) (r = .13) (r = .04) (r = .06)
(r = .00)
** Indicates significance at the 0.01 level.

72

The high correlation values observed between Linear Acceleration (LinAcc) and
Head Injury Criteria (HIC), and Linear Acceleration (LinAcc) and Severity Index (SI)
can be explained by the dependence of HIC and SI calculations on Linear Acceleration.
A high correlation (r=.714) was also observed between Linear Acceleration (LinAcc) and
Angular Acceleration (AngAcc) (Table 10).
Low but significant, correlations for Linear Acceleration (LinAcc) and age
(r=0.307), months of practice (r=0.293), standing height (r=0.349), weight (r=0.232), and
sit and reach flexibility (r=0.282) (Table 11) were found.
Low, but significant, correlations were observed between Angular Acceleration
(LinAcc) and age (r=0.389), months of practice (r=0.376), weight (r=0.249), and sit and
reach flexibility (r=0.281). A moderate and significant correlation was observed between
Angular Acceleration (LinAcc) and standing height (r=0.434).
Also, low, but significant, correlations were found between Severity Index (SI)
and age (r=0.36), months of practice (r=0.314), standing height (r=0.376), weight
(r=0.225), and sit and reach flexibility (r=0.264).
Low, but significant, correlations for Head Injury Criteria (HIC) and age
(r=0.354), months of practice (r=0.319), standing height (r=0.369), weight (r=0.219), and
sit and reach flexibility (r=0.258) were observed.

No significant correlations were

observed for BMI and Linear Acceleration, Angular Acceleration, Head Injury Criteria
and Severity Index.
Correlational analyses were performed for age, height, weight, flexibility, BMI
and months of practice. Results of the correlational analyses for 171 kick trials were
presented in Table 12.

73

Table 12
Sample Pearson Correlation Coefficients (2-Tailed) Among Age, Experience, and
Anthropometry (n=171 kicks)
Height
Weight
Flexibility
BMI
Months of
Practice
Age
Height

.769**

.333**
.680**

.285**
-.076

.876**

.515**

-.494**

Flexibility

.264**
.610**

-.380**

Weight

-.069
.250**

-.096

BMI

.277**

** Indicates significance at the 0.01 level
Low correlations significant at the 0.01 were observed for age and weight (.333),
flexibility (.285) and months of practice (.264). Moderate correlations were observed for
age and height (.769). Low correlations were observed for height and BMI (.250).
Moderate correlations were observed for height and weight (.680) and months of practice
(.610). Low correlations were observed for weight and flexibility (-.380). Moderate
correlations were observed for weight and months of practice (.515). A high correlation
was observed between weight and BMI (.876). A moderate correlation was observed
between flexibility and BMI (-.494). A low correlation was also observed for BMI and
months of practice (.277) (Table 12).
Correlational analyses were performed for age, months of practice, standing
height, weight, flexibility, BMI, considering only maximal values of linear acceleration
(MaxLinAcc), angular acceleration (MaxAngAcc), SI and HIC. Results of the
correlational analyses for 18 participants were presented in Table 13.

74

Table 13
Pearson Correlation Coefficients (2-Tailed) for Maximum Values per Participant, Among
Age, Experience, Anthropometry, Performance Parameters, and Injury Factors (n=18
participants)
Sit and Reach
BMI
Age Months of Standing
Weight
Flexibility
Practice
Height
.496*
.454
.517*
.293
.270
.077
2
2
2
2
2
2
MaxLinAcc
(r = .25) (r = .21) (r = .27) (r = .09) (r = .07)
(r = .00)
MaxAngAcc

.445
.633**
2
2
(r = .20) (r = .40)

.601**
2
(r = .36)

.230
2
(r = .05)

.227
2
(r = .05)

-.045
2
(r = .00)

SI

.499*
.554*
2
2
(r = .31) (r = .25)

.556*
2
(r = .31)

.284
2
(r = .08)

.269
2
(r = .07)

.021
2
(r = .00)

HIC

.527*
.436
2
2
(r = .28) (r = .19)

.517*
2
(r = .27)

.279
2
(r = .08)

.303
2
(r = .09)

.045
2
(r = .00)

* Indicates significance at the 0.05 level.
** Indicates significance at the 0.01 level.
Moderate correlations were observed at the 0.05 level for maximal linear
accelerations, age (r=.496) and standing height (r=.517). Also moderate correlations were
observed at the 0.05 level with SI, age (.554), months of practice (.499) and standing
height (.556). Similarly, moderate correlations were observed for HIC and age (.527), and
standing height (.517) (Table 13). Moderate correlations were observed at the 0.01 level
for maximal angular accelerations, months of practice (r=.663) and standing height
(r=.601) (Table 13).
Results indicated that, only two participants were able to generate dummy head
accelerations greater than 80 g’s in three trials (see Chapter V). Using a more
conservative criteria there were a total of 24 trials by six different participants that
exceeded 42 g’s (see Chapter V). Overall, the results indicated that participants did not
consistently generate linear accelerations close to concussion values failing to reject the
null hypothesis of no difference between maximum impact linear accelerations of the

75

dummy head generated via roundhouse kicks and acceleration values known to cause
concussions in humans.
Testing the hypothesis of no difference between maximum impact angular
accelerations of the dummy head generated via roundhouse kicks and acceleration values
2
known to cause concussions in humans, there were 44 trials exceeding 2000 rad/s and
2
only two participants exceeding the 4420 rad/s threshold (see Chapter V). The results
2
indicated that the 2000 rad/s threshold was exceeded in 25 percent of the cases, thus

presenting a relatively high risk for concussions. This hypothesis was rejected.
To test the null hypothesis of no difference in Linear Acceleration values based
on gender, an Independent-Samples T-Test analysis was performed on LinAcc. The
results (t (169) = 2.55, p<.05) supported the rejection of the null hypothesis and recognize
that there is a difference in Linear Acceleration values associated with gender.
Specifically, female participants showed greater Linear Acceleration than males (Table
14). However, it is important to note that results should not be generalized, due to the
small number of female participants. Additionally, standard deviations were large,
compared to the mean; thus, the spread of the data is significant and indicated a high
level of variability within the sample.
Table 14
Statistics for Maximum Linear Acceleration by Gender
Female
Mean
Std. Deviation
# of Kicks

Male

29.39
29.56
25

19.21
15.86
146

76

To test the null hypothesis of no difference in Angular Acceleration values based
on gender, an Independent-Samples T-Test was performed. No difference in Angular
Acceleration values was found (t (169) = 0.59, p>.05). Thus, the null hypothesis was
supported (Table 15).
Table 15
Means and Standard Deviations for Maximum Angular Acceleration by Gender
Female
1753.82
1374.23
25

Mean
Std. Deviation
# of Kicks

Male
1603.09
1145.37
146

A one-way ANOVA was conducted to determine age differences in Maximum
Linear Acceleration among the three age groups. Age differences were found, F (2, 168)
= 9.6, p<.01. A Tukey Post Hoc test revealed the following differences. The “9 and
under” group showed less acceleration than the “14 and older” group. The “10 to 13”
group exhibited less acceleration than the “14 and older” group. The “9 and under” group
did not differ from the “10 to 13” group (Table 16). The results supported the rejection of
the null hypothesis, indicating that there was a difference in linear acceleration among
age groups with the 14 and older group generating the highest linear accelerations.

Table 16
Linear Acceleration (LinAcc) and Age Group Descriptive Statistics
Age Group
N
Minimum
Maximum
Mean
Std.
(yrs.)
Deviation

Variance

9 and under

42

1.66

47.09

14.01

10.40

108.24

10 to 13

112

2.38

84.81

20.81

19.37

375.27

14 and
older

17

12.30

86.72

36.49

21.60

466.65

77

A One-way ANOVA was conducted to analyze differences in Angular
Acceleration among the three age groups. Significant differences were found, F (2, 168)
= 28.067, p < .01. A Tukey Post Hoc test revealed the following differences. The “9 and
under” group showed less angular acceleration than the “14 and older” group. The “10 to
13” group exhibited less angular acceleration than the “14 and older” group. The “9 and
under” group did not differ from the “10 to 13” group (Table 17). The results supported
the rejection of the null hypothesis, indicating that there was a difference in linear
acceleration among age groups with the 14 and older group generating the highest
angular accelerations.
Table 17
Angular Acceleration (AngAcc) and Age Group Descriptive Statistics
Age
N
Range
Min
Max
Mean
Std.
Group
Dev.
(yrs.)
9 and
42
3240.20 316.20 3556.40
1256.67
831.29
under
10 to
112 3956.20 274.50 4230.70
1498.79 1006.52
13
14 and 17
5370.60 738.60 6109.20
3367.74 1502.75
older

Variance

691057.65
1013097.51
2258279.47

To test the null hypothesis of no differences in linear acceleration values based on
skill level, an Independent-Samples T-Test was performed. Significant differences were
found (t (169) = -2.147, p<.05) with advanced performers having greater linear
acceleration than beginners. Thus, the null hypothesis was rejected (Table 18).

78

Table 18
Means and Standard Deviations for Linear Acceleration by Skill Level
Skill Level
LinAcc

# of Kicks

Mean

Std. Deviation

Std. Error
Mean

Beginner

131

19.02

18.15

1.58

Advanced

40

26.21

19.77

3.12

To test the null hypothesis of no differences in Angular Acceleration values based
on skill level, an Independent-Samples T-Test was performed. Advanced participants had
greater angular acceleration than beginner participants (t (169) = -3.332, p< .01). Thus,
the null hypothesis was rejected (Table 19).
Table 19
Means and Standard Deviations for Maximum Angular Acceleration by Skill Level
Std. Error
Skill Level
# of Kicks
Mean
Std. Deviation
Mean
AngAcc

Beginner

131

1463.93

1038.55

90.73

Advanced

40

2153.02

1443.51

228.24

Multiple regressions analyses for linear and angular accelerations were conducted,
and multicollinearity of variables was also evaluated. The analysis for linear acceleration
included age, height, weight, flexibility, and months of practice as predictors. The results
F (6, 170) = 10.055, p < .05, and R = .519 indicated the model was significant. The
significant predictors were flexibility (β=.502, p<.05), height (β=.403, p<.05) and weight
(β=.285, p<.05). These predictors accounted for 26.9% of the variability. Low partial
correlations were observed for all the predictors. Using the criterion of tolerance values
less than .3 and variance inflation factor (VIF) greater than 3, age, height, months of
practice and skill level indicate multicollinearity among these predictors (Table 20). A
more conventional criteria of VIF >10 indicated no multicollinearity among predictors.

79

Table 20
Linear Acceleration Regression Coefficients and Collinearity
Unstandardized Std. Standardized Partial Tolerance
Model
Coefficients Error Coefficients Correlation
(Beta)
(B)
1 (Constant)
-76.330 30.654
Age
-2.027 1.592
-.183
-.099
.217
Height
68.157 31.807
.403
.165
.126
Weight
.414 .170
.285
.187
.326
1.532 .292
.502
.380
.488
Flexibility
Months of
-.167 .135
-.245
-.096
.113
practice
13.168 6.842
.298
.149
.185
Skill Level

VIF

4.613
7.935
3.066
2.049
8.832
5.391

The analysis for angular acceleration included age, height, weight, flexibility, and
months of practice as predictors. The results F (6, 170) = 14.203, p < .05, and R = .585
indicated the model was significant. The significant predictors were flexibility (β=.470,
p<.05), height (β=.451, p<.05) and skill level (β=.363, p<.05). These predictors
accounted for 34.2% of the variability. Low partial correlations were observed for all the
predictors. Using the criterion of tolerance values less than .3 and variance inflation
factor (VIF) >3, age, height, months of practice and skill level indicate multicollinearity
among these predictors (Table 21). A more conventional criteria of VIF >10 indicates no
multicollinearity among predictors.
Table 21
Angular Acceleration Regression Coefficients and Collinearity
Unstandardized Std. Standardized Partial Tolerance
Model
Coefficients (B) Error Coefficients Correlation
(Beta)
1 (Constant)
-5514.2171828.989
Age
-76.510 94.976
-.110
-.063
.217
.194
.126
Height
4798.5561897.787
.451
Weight
19.495 10.137
.213
.149
.326
Flexibility
90.172 17.394
.470
.375
.488
Months of
-9.827 8.074
-.229
-.095
.113
practice
1006.464 408.209
.363
.189
.185
Skill Level

80

VIF

4.613
7.935
3.066
2.049
8.832
5.391

In summary, several participants (F3, M2, M7, M8, M9, M12, M14 and M15)
were able to generate linear accelerations of the center of gravity of the Hybrid III
dummy head above the threshold of 42 g’s known to cause concussions in adults.
Similarly, there were several participants (F3, M2, M3, M7, M8, M9, M10, M11, M12,
2
M14 and M15) able to exceed the 2000 rad/s threshold for angular accelerations about

the center of gravity of the Hybrid III dummy head known to cause concussions.
Furthermore, two participants (M14 and M15) exceeded the more stringent threshold of
2
4420 rad/s . None of the participants’ trials in the current study exceeded either the

SI=300 or the HIC=250 thresholds.
High correlation values were observed between linear and angular accelerations.
Low, but significant, correlations were observed for linear acceleration and age, months
of practice, standing height, weight and flexibility. Similarly, low, but significant,
correlations were observed for angular acceleration and age, months of practice, weight
and flexibility. A moderate and significant correlation was observed between angular
acceleration and standing height.
Results showed that there is a difference in linear acceleration values associated
with gender. Specifically, female participants generated greater linear accelerations than
males. No differences in angular accelerations were observed for gender.
Differences in linear accelerations among age groups were observed, and results
indicated the 14 and older group as the one that generated the highest linear accelerations.
Differences were also observed for skill level, and advanced performers were identified
as the group that generated the highest linear accelerations.

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Results showed a difference in angular accelerations among age groups,
identifying the 14 and older group as the one that generated the highest angular
accelerations. Differences by skill level indicated that advanced performers also
generated the highest angular accelerations.
Analysis of multicollinearity of predictors of linear acceleration (age, height,
weight, flexibility, and months of practice) indicated moderate values among these
predictors. Similarly, analysis of predictors of angular acceleration (age, height, weight,
flexibility, and months of practice) also indicated moderate values.

82

CHAPTER V
Discussion and Conclusions
Linear Acceleration

A linear acceleration of 80 to 90 g’s acting for more than four milliseconds can lead to
concussions (Guskievicz and Mihalik, 2006). Based only on the linear acceleration
criterion, results of the current study indicated that only two participants using a
roundhouse kick were able to achieve an acceleration greater than 80 g’s to the head of
the dummy. One of these participants was 12 year old female beginner (F3) who
achieved values of 83.76 and 84.81 g’s. The other participant was an advanced 14 year
old male (M15) who reached a value of 86.72 (Table 19). Pellman, Viano, Tucker,
Casson, and Waeckerle (2003) reported more stringent values (42-80 g’s) as the limits of
tolerable translational acceleration of the head in humans. These authors also reported
that values greater than 60 g’s have been considered critical to cause concussions. Under
this range (42-80 g’s) there were ten trials by one female (F3) and 14 total trials by a
combination of six beginning (M2, M7, M8, M9, M12, M14) and one advanced (M15)
male participants that exceeded 42 g’s (Table 22).
Overall, the results indicated that participants did not consistently generate linear
accelerations close to concussion values, but nevertheless are capable of doing so. Low g
values may be explained by the inability of participants to consistently hit the target (as it
was observed during data collection), either by the lack of familiarity with the testing
setup or by a limited kicking ability. Analyses indicated that female participants’ values
were greater than males, in spite of being beginners. Possible explanations for this can be
associated with female participants reaching puberty earlier than male participants

83

(resulting in higher weight associated with an increase in muscle and fat mass) (Malina,
Bouchard, & Bar-Or, 2004), and also exhibiting greater flexibility of the lower
extremities, which may facilitate the generation of velocity in the lower extremity and
greater ability to kick targets at head level.
When examining the sitting height to standing height ratios, the three female
participants (F1, F2, F3) had a ratio greater than 0.5; thus this cannot be considered a
significant factor to explain the difference in linear accelerations because ten of the male
participants (M1, M2, M4, M5, M8, M9, M10, M12, M13, M14) had a ratio greater than
0.5. Furthermore, the average female participant was shorter (mean 139.2 cm for females
and 148.21 cm for males) and lighter (mean weight was 38.55 kg for females and 50.07
kg for males) than the average male. When compared with the corresponding female
Body Mass Indices (BMI) for age percentiles, the two 11 year olds (F1, F2) had a BMI
th
below the 50 percentile for their age group (16.7), while the 12 year old (F3) was
th
classified in the 90 percentile for her age group. Mean sit and reach flexibility was 6.5

cm for the females and -1.2 cm for the males, indicating that female participants were
more flexible than their male counterparts. Based on these observations, BMI may not
explain the differences in linear accelerations. However, a wider range of motion of the
lower back and lower extremities may explain some of these variations.

84

Table 22
Linear Acceleration (Participants Exceeding 42 g’s)
Participant ID
Gender
Age (yrs.)
F3
Female
12

M2
M8

Male

Skill Level
Beginner

9
10

Advanced
Beginner

M9

10

advanced

M12
M14
M15

12
14
14

beginner
beginner
advanced

85

Linear Acceleration (g)
83.76
74.03
49.11
60.13
70.55
44.66
65.42
84.81
43.79
53.24
47.09
49.17
61.68
46.68
59.73
54.36
43.41
45.73
47.61
44.14
56.44
56.08
75.49
86.72

Angular Acceleration

Guskievicz and Mihalik (2006) identified linear acceleration and deceleration and/or
rotation of the skull as the basic concussion mechanisms and categorized these
mechanisms into head-contact injuries and head-movement injuries. Several thresholds
for angular accelerations to cause concussions have been identified by Hardy, Foster,
2
Mason, Yang, King, and Tashman’s (2001) (2000 rad/s ), Zhang, Dwarampudi, Yang,
2
and King’s (2003) (6398 ±1978 rad/s ), Ommaya, Goldsmith, and Thibault (2002) (4500
2
2
rad/s ) and Pellman, Viano, Tucker, Casson, and Waeckerle (2003) (6596 ±1866 rad/s ).

There were ten female (F3) and 34 male (M2, M3, M7, M8, M9, M10, M11, M12, M14,
2
M15) trials exceeding the 2000 rad/s values (Table 23). No female participants reached
2
the threshold of 4420 rad/s cited by Zhang, Dwarampudi, Yang, and King (2003) and

only one male beginner (M14) with one kick and one advanced participant (M15) with
2
three kicks exceeding the 4420 rad/s threshold, and Pellman’s et al. (2003) lowest value
2
2
of 4730 rad/s . Using the first criteria of 2000 rad/s , the results indicated that this

threshold was exceeded in 25 percent of the cases, thus presenting a relatively high risk
for concussions to participants receiving a roundhouse kick, regardless of age, gender, or
skill level. Most of the participants did not reach the threshold obtained by Zhang and
2
colleagues of 6398 ±1978 rad/s . However, it is likely for some participants who are

86

older and more skilled to reach these values and cause a concussion to their opponents
from their roundhouse kicks.
Being older is associated with an advanced mature physical state that manifests
itself in a greater muscle mass (particularly in males), and thus a greater ability to
generate force that can be transmitted through kicks (faster movements and greater
momentum of the kicking segment). In a study of adult boxers, Waliko, Viano, and Bir
(2005) reported a linear correlation between weight class, and rotational accelerations,
thus providing an insight on the relationships between weight, force of impact and the
resulting head accelerations.
Skill proficiency of participants particularly those with advanced levels, provides
another explanation for the results observed. Theorists in motor development recognize
that advanced level participants will be more efficient, faster, and demonstrate more
control of the motor skills required for a sport (Schmidt & Wrisberg, 2008), thus in this
project, advanced participants were able to transmit more force through their kicks.

87

Table 23
2
Angular Acceleration (Participants Exceeding 2000 rad/sec )
Participant
Angular Acceleration
Gender
Age (yrs.)
Skill Level
2
ID
(rad/s )
F3
female
12
beginner
3181.7

3105.7
3158.4
2125.5
3570.9
3429.7
3598.5
3649.9
3698.1
3991.9
M2

male

9

beginner

3556.4
4154.0

M3

9

advanced

2089.4
2730.7
2365.4
2805.4
2448.0
3300.9

M7

10

beginner

2161.8

M8

10

beginner

3426.3
2258.1
4229.4
3070.2
3240.3

M9

10

advanced

3787.4
2586.2
2971.2

M10

11

beginner

88

4230.7

Table 23 (cont’d)
M11

11

beginner

2418.8
2187.1
3251.4

M12

12

beginner

2899.4

M14

14

beginner

3203.9
3072.4
3260.9
3507.8
4185.8
4472.2

M15

14

advanced

5351.8
3726.0
2892.7
3115.4
5181.8
6109.2

Severity Index (SI) and Head Injury Criteria (HIC)

Pellman, Viano, Tucker, Casson, and Waeckerle (2003) reproduced game impacts
and injuries that produced concussions in professional football players and identified
values of 300 for SI and 250 HIC as nominal values for concussions (for helmet impacts).
King (2000) reported values ≤ 1000 for SI and HIC as acceptable (under the automotive
safety industry standards). Under the Abbreviated Injury Scale (AIS) for rating injuries
by the Insurance Institute of Highway Safety (2009), a HIC-15 (Head Injury Criteria
evaluated over a period of 15 ms) of 700 can indicate a higher risk of injury. None of the
participants’ trials in the current study exceeded either the SI=300 or the HIC=250.

89

The aforementioned HIC and SI thresholds have been developed by and for the
automotive industry where the nature of the impacts is a result of an interaction (direct or
indirect) of humans and vehicles. They were not created to assess impacts between
humans. However, they provided models that can be modified to consider these
conditions. At this point, the results did not meet the criteria to consider the impact to the
dummy head as significant for a high risk of injury. More research is needed to
effectively adapt these scales to assess the potential for concussions.
Conclusions

Results provided insight on the ability of children to generate linear and angular
accelerations on a Hybrid III female dummy head and the risk of concussion. It may be
possible that the linear and angular acceleration thresholds for concussions for children
be smaller than those used for comparisons in this study (collected from concussions in
NFL players) thus the results must be observed with caution because no data are available
for children.
The results indicated that participants were capable of reaching thresholds for
linear and angular accelerations known to cause concussions, although not consistently.
Thus, further research is needed to explain the risks of concussion in martial arts from
kicks to the head in this population.
Results also showed that female participants did generate higher linear
acceleration values than male participants. Analyses showed differences by age group
where older participants generated higher maximal linear and angular accelerations.
Skilled participants also generated greater maximal linear and angular accelerations than
beginners.

90

Some participants were able, with their roundhouse kicks, to reach the threshold
known to cause concussions in humans. Age, months of practice, standing height, weight,
and sit and reach flexibility showed low, but significant, correlations with maximum
linear and angular accelerations of the dummy head suggesting that these variables may
not be related to these accelerations. However, significant differences between skill
levels, suggested that advanced performers generated greater maximum linear and
angular accelerations than beginners. Gender differences in maximum linear and angular
accelerations of the dummy head generated via roundhouse kicks did show differences,
but results were limited by the small sample size.
Practical Implications

Martial arts are a popular choice as a physical activity for children. However, it is
necessary to educate parents, instructors, and governing bodies about the intrinsic risk for
traumatic brain injuries, which has been reported to be similar to other contact sports
such as American football, boxing, and ice hockey. Thus, providing parents with more
evidence to make decisions when selecting a martial arts program, and providing
instructors and organizations insight into potentially offering better services to their
communities.
Martial arts programs can benefit by promoting non-contact sparring programs,
particularly for children. Safer environments can translate into more participants and even
participation extending over a period of several years, impacting not only self-esteem,
socialization, and fitness of participants, but an increased income for studio owners.

91

Children are capable of generating linear and angular accelerations high enough
to cause concussion with their roundhouse kicks to the head. Thus, it is suggested to
reduce the number of practice sessions or tournaments that encourage kicks to the head.
The use of head gear and mouth guards is strongly recommended in practice and
competition, but is important to recognize that this gear only reduces the risk of fractures
of the skull and may not sufficiently reduce the linear and angular accelerations that the
brain experiences as a result of an impact to the head to eliminate concussions. These
accelerations are the contributing factors to concussions, thus the use of head gear may
give a false sense of protection against concussions.
The long term effects of single/multiple concussions in children are not known at
this time; however recent studies on contact sports, particularly American football, are
pointing to negative effects on cognition, memory, irritability, sudden bursts of rage, and
number of cases of depression (Rabadi and Jordan, 2001). Thus, it is suggested to reduce
children exposure to these risks. In martial arts this can be accomplished by reducing the
exposure to kicks to the head in practice and competition. By modifying competition
rules, promoting controlled (low impact) kicks to the head or discouraging the use of
competition systems that award higher scores for full force impacts, not promoting
knockout of an opponent, and/or having a differential scoring system in place where more
points are not awarded when complex kicks (adding jumps and body turns) are used to
impact the head of an opponent. These complex kicks typically have a greater moment of
inertia that may contribute to higher accelerations of the brain after an impact, and may
cause a more serious injury.

92

It is also recommended that safety training modules for athletes, parents, and
instructors be developed on the health risks associated with concussions, the possible
negative long term effects of concussion, and how to identify them in competition or
practice. Furthermore, becoming familiar with guidelines that dictate when a participant
can go back to the activity and developing a surveillance system to monitor the incidence
of this type of injury will contribute to a safer participation in martial arts.
Recommendations for Further Study

It is important to continue exploring the effects of these variables on concussion
by conducting similar studies that focus on increasing the number of participants by
gender, age, skill level, and control for martial art style. Including participants from
martial arts that emphasize kicking over punching such as taekwondo and muay thai, may
provide a better understanding of high injury rates reported by Pieter et al. (1995), and
Pieter and Zemper (1998). These styles promote the use of kicking techniques to the
head, and knocking out an opponent is one of the goals of the competition.
The accelerations resulting from other kicking techniques need to be studied.
Among these are front and crescent kicks (for the simplicity), and particularly those that
include whole body rotations along the longitudinal axis of the kicker, such as back and
reverse hook kicks. These kicks have been reported to be not as fast or popular as
roundhouse, but are used effectively in competition, due to their devastating effects if the
head is impacted.
Although the results of this study of the roundhouse kick to the Hybrid III female
dummy head showed most linear and angular accelerations lower than the thresholds
known to cause concussions, the effects of receiving one or several kicks to the head

93

during martial arts competitions or practice settings need to be studied further, because
there may be cumulative effects on the brain even at lower acceleration levels, which
may predispose participants to concussions, or more severe brain injuries. Further
understanding is also needed for “second impact syndrome”, which can occur when a
practitioner receives an impact to the head and falls uncontrolled or unconscious to the
ground, thus exposing him/her to a second impact, this time against the floor (which
could be padded or not), potentially contributing to a more serious outcome.

94

APPENDICES

95

Appendix A
Parental Consent Form Michigan State University

“Accelerations of a Hybrid III Dummy Head Resulting From Roundhouse Kick Impacts
and Their Relation to the Risks of Concussions in Boys and Girls”
Your child is being asked to participate in a research study. The purposes of this
study are to compare the magnitudes of impacts by a roundhouse kick, measured on a
Hybrid III head dummy, to those that are known to cause concussions. This study will
attempt to identify differences in performances of practitioners with various skill levels,
ages, and gender.
Your child is being asked to participate in this study because s/he has been
participating in martial arts for 4 or more weeks (or at least 8 hrs). Your child’s
participation is totally voluntary, and s/he may refuse to participate in certain procedures
or answer certain questions as well as to discontinue participation at any time without any
explanation. There is no direct economic benefit to you or your child from your child’s
participation. By allowing your child to participate in this study you agree that the
materials and data generated (pictures, video and measurements) may be used for
research and academic purposes. Please note that your child cannot be in the study
without being taped. Only the research team members, the Human Investigation
Committee at Wayne State University and the Michigan State University’s Human
Research Protection Program will have access to the research data. Your child’s
confidentiality will be protected to the maximum extent allowable by law. We will keep
your child’s records private unless we are required by law to share any information. Any
films or pictures shown in research presentations will be deidentified with faces not
visible. After completion of the project, all research data will be stored securely for a
period of 3 years under the supervision of Dr. Marty Ewing at the Department of
Kinesiology at Michigan State University. When this research is completed, an abstract
of the results will be mailed to you.
The participants must be free of any orthopedic condition that may hinder their
ability to perform roundhouse kicks, the data collection session will last approximately 1
hour and participants will be asked to participate in only one data collection session. Data
collection will have the following stages:
1.
General information.
Your child will be asked to complete a questionnaire in order to provide general
information about himself/herself such as name, date of birth, gender, martial arts
experience, leg predominance, practice time, competition experience and overall physical
activity.

96

2.

Anthropometrical measurements and flexibility.
All anthropometric data will be collected in private (parents or guardians may be
present) in the Sports Injury Biomechanics Lab at Wayne State University’s Department
of Biomedical Engineering.
•
Weight will be assessed on a standard weight balance while your child wearing
only shorts and
t-shirt.
•
Height will be assessed with a standard stadiometer.
•
Sitting height will be assessed with a standard stadiometer while you are seated
on a bench.
•
Segmental lengths will be assessed with the use of standard body calipers. Thigh,
shank, and foot lengths will be taken.
•
Biacromial and bicristal widths will also be measured with a body caliper.
•
Flexibility will be measured with the sit-and-reach test.
3.

Kinetic data collection
Kinetic data collection (data related to velocities and accelerations experienced by
a dummy head) will involve the use of a Hybrid III dummy and the BAF system will
collect kinematic data through your child’s kick attempts; a backup high-speed video
system will be used to record performances. The following protocol will be used:
•
Your child will be asked to warm up as if you were about to participate in one of
your standard
Martial arts practice sessions.
•
Following your child’s overall warm up, your child will be asked to perform 5
roundhouse kicks according to
how your child would normally perform them. (Note that there is no correct or incorrect
performance. We only want to record your child’s style of performance.) Your child
will be asked to
assume a “ready sparring position” prior to kicking the side of a Hybrid III crash dummy
head that has been adjusted to your child’s height.
•
Your child will be asked to do 5 trials of the technique with each foot. Each trial
will be recorded.
There will be no direct benefit to your child from participating in this study.
However, the study will help to identify differences that may lead to improve teaching
techniques, reduction of injuries, and promote safer martial arts.
Risks associated with your child’s participation in this study may include bruises
on your child’s feet as a result of kicking the dummy head (even though your child will
be wearing protective equipment on his/her feet, and the head will be fitted with
protective gear too), or “pulling a muscle” while kicking, however, this risk is no
different from a normal martial arts practice session. No other serious risks are identified
at this time.

97

In the event that this research related activity results in an injury, treatment will be
available including first aid, emergency treatment and follow-up care as needed. Care for
such will be billed in the ordinary manner to you or your insurance company. No
reimbursement, compensation or free medical care is offered by Wayne State University
or Michigan State University. This does not mean that you are giving up any legal right
you may have. If you think that your child may have suffered a research related injury
you may contact Dr. Cynthia Bir
no. (313)577-3830, Dr. Marty Ewing
no.
(517)353-4652, or Miguel Narvaez no. (716)372-2233.
If you have questions or concerns about your child’s role and rights as a research
participant, would like to obtain information or offer input, or would like to register a
complaint about this study, you may contact, anonymously if you wish, the Michigan
State University’s Human Research Protection Program by phone: (517)355-2180, fax:
(517) 432-4503, e-mail: irb@msu.edu, or regular mail at 207 Olds Hall, MSU, East
Lansing, MI 48824, or the Chair of the Human Investigation Committee at Wayne State
University no.(313) 577-1628. If you are unable to contact the research staff, or if you
want to talk to someone other than the research staff, you may also call no. (313) 5771628.
Name of participant:___________________________________
Date of birth:____________

Date:___________

Name of parent/guardian:___________________________________________________
I voluntarily agree to allow my child to participate in the study. (Signature of
parent/guardian): _________________________
Mailing
address:_________________________________________________________________
Phone:_______________ e-mail address:_____________________________________

98

Appendix B
Research Consent Form Wayne State University

Title of the Study: Accelerations of a Hybrid III Dummy Head Resulting From
Roundhouse Kick Impacts and Their Relation to the Risks of Concussions in Boys and
Girls.
Principal Investigator (PI):

Cynthia Bir
Department of Biomedical Engineering
(313)577-3830

When we say “you” in this consent form, we mean you or your child; “we” means the
researchers and other staff.
Purpose
The purposes of this study are to compare the magnitudes of linear acceleration of
the center of gravity of the head and angular acceleration about the center of gravity from
a hybrid III head dummy as a result of being impacted with a roundhouse kick, to values
of these same variables that are known in general to cause concussions as a result of
direct contact with the head. It will attempt to identify differences in performances of
practitioners with various skill levels, ages, and gender. The roundhouse kick is
considered a simple kick in the martial arts, and the study will help to identify
performance differences that may lead to the improvement of teaching techniques,
reduction of risk of injury, and promotion of a safer activity.

The data collection session will last approximately 1 hour and participants will be
asked to participate in only one data collection session, also participants must be free of
any orthopedic condition that may hinder their ability to perform kicks. It is estimated to
have 60 participants in the project. Data collection will have the following stages:
Study Procedures
1.
General information.
You will be asked to complete a questionnaire in order to provide general information
about yourself such as name, date of birth, gender, martial arts experience, leg
predominance, practice time, competition experience and overall physical activity.
2.
Anthropometrical measurements.
All anthropometric data will be collected in private (parents or guardians may accompany
you) in the Sports Injury Biomechanics Lab at Wayne State University’s Department of
Biomedical Engineering.
•
Weight will be assessed on a standard weight balance while you are wearing only
shorts and
t-shirt.
•
Height will be assessed with a standard stadiometer.

99

•
Sitting height will be assessed with a standard stadiometer while you are seated
on a bench.
•
Segmental lengths will be assessed with the use of standard body calipers.
Thigh, shank, and foot lengths will be taken.

3.

Kinetic data collection
Kinetic data collection will involve the use of a Hybrid III dummy and the BAF
system will collect kinematic data through your kick attempts. A high-speed video
system will also be used as a backup for the BAF system. The following protocol will be
used:
•
You will be asked to warm up as if you were about to participate in one of your
standard
Martial arts practice sessions.
•
Following your overall warm up, you will be asked to perform 5 roundhouse
kicks according to
how you would normally perform them. (Note that there is no correct or incorrect
performance. We only want to record your style of performance.) You will be asked to
assume a “ready sparring position” prior to kicking the side of a Hybrid III crash dummy
head that has been adjusted to your height.
•
You will be asked to do 5 trials of the technique with each foot. Each trial will be
recorded.
Benefits
You are being asked to participate in this study because of you have been
participating in martial arts for 4 or more weeks (or at least 8 hrs). As a participant in this
research study, there will be no direct benefit for you; however, information from this
study may benefit other people now or in the future.
Risks

There are no known risks at this time to participation in this study.
Study Costs
Participation in this study will be of no cost to you.
Research Related Injuries
In the event that this research related activity results in an injury, treatment will be
made available including first aid, emergency treatment, and follow-up care as needed.
Care for such will be billed in the ordinary manner to you or your insurance company. No
reimbursement, compensation, or free medical care is offered by Wayne State University.
You may contact Dr. Cynthia Bir
no. (313)577-3830, Dr. Marty Ewing
no.
(517)353-4652, or Miguel Narvaez no. (716)372-2233 with any questions or to report
an injury.

100

Confidentiality
All information collected about you during the course of this study will be kept
confidential to the extent permitted by law. You will be identified in the research records
by a code name or number. Information that identifies you personally will not be released
without your written permission. However, the study sponsor, the Human Investigation
Committee (HIC) at Wayne State University, or federal agencies with appropriate
regulatory oversight [e.g., Food and Drug Administration (FDA), Office for Human
Research Protections (OHRP), Office of Civil Rights (OCR), etc.) may review your
records.

When the results of this research are published or discussed in conferences, no
information will be included that would reveal your identity.
If photographs, or video recordings of you will be used for research or educational
purposes, your identity will be protected or disguised. All the materials will be kept in a
locked cabinet under the supervision of the PI, and will be destroyed after three years.
Only coded information will be used for analysis and it will not be possible to identify
you or your data.
Voluntary Participation/Withdrawal
Taking part in this study is voluntary. You have the right to choose not to take
part in this study. You are free to only answer questions that you want to answer. You
are free to withdraw from participation in this study at any time. Your decisions will not
change any present or future relationship with Wayne State University or its affiliates, or
other services you are entitled to receive.

The PI may stop your participation in this study without your consent. The PI will
make the decision and let you know if it is not possible for you to continue. The decision
that is made is to protect your health and safety, or because you did not follow the
instructions to take part in the study
Questions
If you have concerns or any questions about this study, such as scientific issues,
how to do any part of it, or to report an injury, please contact the researchers Dr. Marty
Ewing no. (517)353-4652, email: mewing@msu.edu at the Department of Kinesiology
at Michigan State University, or Miguel Narvaez
no. (716)372-2233, email:
narvaezm@sbu.edu at the Department of Physical Education at Saint Bonaventure
University. If you have questions or concerns about your role and rights as a research
participant, would you like to obtain information or offer input, or would you like to
register a complaint about this study, you may contact, anonymously if you wish, the
Michigan State University’s Human Research Protection Program by phone: (517)3552180, fax: (517) 432-4503, e-mail: irb@msu.edu, or regular mail at 207 Olds Hall, MSU,
East Lansing, MI 48824, the Chair of the Human Investigation Committee at Wayne
State University no.(313) 577-1628. If you are unable to contact the research staff, or
if you want to talk to someone other than the research staff, you may also call no.
(313) 577-1628 to ask questions or voice concerns or complaints.

101

.Consent to Participate in a Research Study
To voluntarily agree to take part in this study, you must sign on the line below. If
you choose to take part in this study you may withdraw at any time. You are not giving
up any of your legal rights by signing this form. Your signature below indicates that you
have read, or had read to you, this entire consent form, including the risks and benefits,
and have had all of your questions answered. You will be given a copy of this consent
form.
___________________________________
Signature of participant

_____________
Date

___________________________________
Printed name of participant

_____________
Time

___________________________________
Signature of witness**

_____________
Date

___________________________________
Printed of witness**

_____________
Time

___________________________________
Signature of person obtaining consent

_____________
Date

___________________________________
Printed name of person obtaining consent

_____________
Time

102

Appendix C
Verbal Assent Script Wayne State University
Project Title: “Accelerations of a Hybrid III Dummy Head Resulting From Roundhouse
Kick Impacts and Their Relation to the Risks of Concussions in Boys and Girls”
Principal Investigators:
Cynthia Bir Ph.D.
Marty Ewing Ph.D.
Miguel Narvaez

My name is Miguel Narvaez.
We want to tell you about a research study we are doing. A research study is
usually done to find a better way to treat people or to understand how things work. In this
study, we want to find out more about how a head moves and reacts after being hit with a
roundhouse kick. You are being asked to be in this study because you have been
practicing a martial art for at least 8 hours, you are between 5 and 17 years of age and can
perform a roundhouse kick without any problems. In any study, only people who want to
take part are allowed to do so. You do not have to be in this study if you do not want to
do so.
If it is okay with you and you agree to join this study, you will be asked to
complete a questionnaire about your age, your martial arts experience and overall
physical activity. You can ask for help from your parent(s).
You height, weight and length of your arms and legs will be also measured.
Some sensors will be placed in your trunk, arms and legs that will allow us to record the
movement of these parts of your body while you are asked to use a roundhouse kick to hit
a special dummy head. We will also use high-speed video cameras to record your
performance.
You will be asked to kick the dummy head 5 times with each leg.
You only need to come here once, and all these measurements will take about an hour to
complete.
As a result of kicking the dummy head you may get a bruise on your kicking foot
(note that you will be wearing protective equipment on your feet), or “pull a muscle”
while kicking, however, this risk is no different from a normal martial arts practice
session. No other serious risks can be identified.
If anything hurts or you are uncomfortable with some of the questions, please let us
know, you can stop to participate at any time.
We do not know if you will be helped by being in this study however the study
will help to identify differences that may lead to improve teaching techniques, reduction
of injuries, and promote safer martial arts.

103

You do not have to be in this study. It is up to you. You can say no now or you
can change your mind later. All you have to do is tell us. No one will be mad at you if
you change your mind.
Your parents/guardian say it is okay for you to be in this study. If you have
questions, please ask them now or at anytime.
We will make every reasonable to keep your information confidential. But we do
have to let some people look at your study records. We will keep your records private
unless we are required by law to share any information. The law says we have to tell
someone if you might hurt yourself or someone else. The study researchers can use the
study results as long as you cannot be identified. Any films or pictures shown in research
presentations will be deidentified with faces not visible. Information that identifies you
personally will not be released without you written permission. However, the Human
Investigation Committee (HIC) at Wayne State University, The Institutional Review
Board (IRB) at Michigan State University or federal agencies with appropriate regulatory
oversight, may review your records.
If you are not happy with this study and want to talk to someone else other than
the research personnel please call Dr. Cynthia Bir at (313)577-3830, Dr. Marty Ewing at
(517)353-4652 or Miguel Narvaez (716)372-2233 with any questions or to report an
injury. If you have questions or concerns about your rights as a research participant
contact the Wayne State University Chair of the Human Investigation Committee at
(313)577-1628 or Michigan State University Human Research Protection Program at
(517)355-2180.
Do you understand this study and are you willing to be in it?

To be completed by person obtaining verbal assent from the child/subject:
Yes
No
Child’s/Subject’s response:
Check which applies below:

The child/Subject is capable of understanding the study
The child/Subject is not capable of understanding the study

Child’s/Subject’s Name (printed)

Signature of Person Obtaining Verbal Assent

104

Date

Appendix D
Adolescent Assent Form Wayne State University

Title: “Accelerations of a Hybrid III Dummy Head Resulting From Roundhouse Kick
Impacts and Their Relation to the Risks of Concussions in Boys and Girls”
Study Investigators:
Cynthia Bir Ph.D.
Marty Ewing Ph.D.
Miguel Narvaez
Why am I here?
This is a research study. Only people who choose to take part are included in research
studies. You are being asked to take part in this study because you have been an active
martial arts participant in the last four weeks, have accumulated at least eight hours of
practice during this time frame, are between five and 17 years of age, and you are
healthy, without any abnormalities or injuries that may adversely affect performance of
the roundhouse kick. Please take time to make your decision. Talk to your family about
it and be sure to ask questions about anything you don’t understand.
Why are they doing this study?
This study is being done to find out how a hybrid III head dummy responds (its velocities
and accelerations will be estimated) after being kicked with a roundhouse kick and
compare them with known values that can cause concussions. It will attempt to identify
differences among practitioners of various skill levels, age, and gender.
What will happen to me?
You will complete a questionnaire about your age, your martial arts experience and
overall physical activity. You can ask for help from your parent(s).
You height, weight and length of your arms and legs will be also measured.
Some sensors will be placed in your trunk, arms and legs that will allow us to record the
movement of these parts of your body while you are asked to use a roundhouse kick to hit
a special dummy head. We will record your performance with high speed video cameras.
You will be asked to kick the dummy head 5 times with each leg.
How long will I be in the study?
You will be in the study for only one hour, and only need to visit once.
Will the study help me?
We cannot promise you that being in this research study will help you, however the study
will help to identify differences that may lead to improve teaching techniques, reduction
of injuries, and promote safer martial arts.

105

Will the study hurt?
As a result of kicking the dummy head you may get a bruise on your kicking foot (note
that you will be wearing protective equipment on your feet), or “pull a muscle” while
kicking, however, this risk is no different from a normal martial arts practice session. No
other serious risks can be identified.
Research Related Injuries:
In the event that this research related activity results in an injury, treatment will be
available including first aid, emergency treatment and follow-up care as needed. Care for
such will be billed in the ordinary manner to you or your insurance company. No
reimbursement, compensation or free medical care is offered by Wayne State University
or Michigan State University. If you think that you have suffered a research related
injury, let the investigator know right away.
Do my parents or guardians know about this?
This study was explained to your parents/guardian and they said that you could be in it.
You can talk this over with them before you decide.
What about confidentiality?
Every reasonable effort will be made to keep your medical records confidential. But we
do have to let some people look at your study records. We will keep your records private
unless we are required by law to share any information. The law says we have to tell
someone if you might hurt yourself or someone else. The study researchers can use the
study results as long as you cannot be identified. Any films or pictures shown in research
presentations will be deidentified with faces not visible. Information that identifies you
personally will not be released without you written permission. However, the Human
Investigation Committee (HIC) at Wayne State University, The Institutional Review
Board (IRB) at Michigan State University or federal agencies with appropriate regulatory
oversight, may review your records.
What if I have any questions?
For questions about the study please call Dr. Cynthia Bir at (313)577-3830, or Dr. Marty
Ewing at (517)353-4652 or Miguel Narvaez (716)372-2233 with any questions or to
report an injury. If you have questions or concerns about your rights as a research
participant contact the Wayne State University Chair of the Human Investigation
Committee at (313)577-1628 or Michigan State University Human Research Protection
Program at (517)355-2180.
Do I have to be in the study?
You don’t have to be in this study if you don’t want to or you can stop being in the study
at any time. Please discuss your decision with your parents and the researchers. No one
will be angry if you decide to stop being in the study.

106

AGREEMENT TO BE IN THE STUDY
Your signature below means that you have read the above information about the study
and have had a chance to ask questions to help you understand what you will do in this
study. Your signature also means that you have been told that you can change your mind
later and withdraw if you want to. By signing this assent form you are not giving up any
of your legal rights. You will be given a copy of this form.
_________________________________
Signature of Participant (13 yrs & older)

_______________
Date

________________________________________________
Printed name of Participant (13 yrs & older)
___________________________________
**Signature of Witness (When applicable)

__________________
Date

__________________________________________________________
Printed Name of Witness
___________________________________
Signature of Person who explained this form

______________
Date

________________________________________________
Printed Name of Person who explained form
** Use when participant has had consent form read to them (i.e., illiterate, legally blind,
translated into foreign language).

107

Appendix E
Data Collection Form (Demographics)

Date:_______________

ID No.:________

Name:__________________________________________ Date of Birth:_________
Gender:__________Rank (Kup/Dan):__________ Belt Color:___________
Leg predominance: _________________________
How many months have you been practicing martial arts? _________
In the last month, how many hours per week have you practiced martial arts?
_________
In the last week, how many hours have you practiced martial arts? _________
Using the following table, tell us how many competitions you participated in during the
past year, and what was the nature of each competition. Also indicate if you finished in
the top ten participants in each contest.
martial arts Only
Mixed
Martial Arts
Full-contact
Non-Contact
Forms
Describe
sparring
sparring
Weight/skill
division
Approx. #
participants in your
category
Approx. # of
matches you
participated
Final placement
Did you suffer any
injuries that require
you to miss at least
one practice
session? (describe)
How many hours per week do you invest in preparing/practicing for free-sparring
competitions? ___________________________________
How many hours per week do you invest in preparing/practicing for form competitions?
______________________________________

108

Use the following table to tell us about any other physical activities that you may do
during your week.
List any other
sport(s) of
physical
activities that
you participate
in

For each
sport/activity
indicate the
frequency and
number of
hours you
practice it per
week

If you
Please number
Have you
compete in
these activities suffer any
any of these,
in your
injuries in
please indicate favorite order
these
the level of
of preference,
activities
participation starting with 1 that required
(school clubs,
as being the
you to miss
community
most favorite. at least one
clubs, junior
practice
varsity, varsity
session?
sports, etc.)
(describe)

109

Appendix F
Data Sheet

Date:_________________________

ID No.:_______________________

Name
DOB mm/dd/yy
Gender
ID number
(ddmmyygbddmmyy)
Sitting height (m):
(measure to the
closest mm)
Standing height (m):
(measure to the
closest mm)
Shoulder height (m):
(measure to the
closest mm)
Trochanteric height
(m):
(measure to the
closest mm)
Leg length (m):
(measure to the
closest mm)
Weight (kg):
(measure to the
closest hundredth)
Flexibility (cm):
(measure to the
closest mm)
Biacromial width
(cm):
(measure to the
closest mm)
Bicristal width (cm):
(measure to the
closest mm)

110

Appendix G
Glossary

To understand concepts presented throughout this document, the following
definitions are provided:
Abrasion: Minor wound in which the surface of the skin or mucous membrane is worn
away by rubbing or scraping.
Abbreviated Injury Scale (AIS): The AIS was originally designed to stratify victims of
motor vehicle crashes. The AIS injury severity values are consensus-derived and range
from 1 (minor) to 6 (fatal).
Accelerometer: An instrument used to measure acceleration.
Angular acceleration: The rate of change of angular velocity over time.
Angular velocity: The rate of change of the angular position of a rotating body over time.
Anthropometry: The measurement of the structures and proportions of the human body.
Apnea: Transient cessation of respiration.
Ataxia: An inability to coordinate voluntary muscular movements that is symptomatic of
some central nervous system disorders and injuries and not due to muscle weakness.
Athlete-Exposure (A-E): An epidemiologic concept of person-time at risk, thus describing
the time or times an athlete is at risk of an injury by participating in his/her sport.
Athlete-game: An injury incidence density rate that considers one-athlete participation in
a game.
Athlete-practice: An injury incidence density rate that considers one-athlete participation
in a practice.

111

Athletic Injury Monitoring System (AIMS): An injury surveillance system established by
the NCAA to provide data on injury rates, patterns, and risk factors of various sports.
Avulsion: Tearing or forcible separation of part of a structure.
Body Mass Index (BMI): Is an index for relating a person's body weight to their height.
Chronic Traumatic Brain Injury (CTBI): A condition characterized by persistent brain
damage or dysfunction as sequelae of cranial trauma.
Collision sports: A sport in which the athletes purposely hit or collide with each other or
inanimate objects, including the ground, with great force.
Contact sports: A sport in which body contact either is an integral component of the sport
or commonly occurs while engaged in the sport.
Contusion (bruise): An area of skin discoloration caused by the escape of blood from
ruptured underlying vessels following injury.
Coup/counter coup cavitation: Injury to the brain occurring directly beneath the area of
impact.
Diencephalon: The posterior part of the forebrain, consisting of the hypothalamus,
thalamus, metathalamus, and epithalamus.
Diffuse Axonal Injury (DAI): A relatively common sequela of blunt head injury,
characterized by a global disruption of axons throughout the brain.
Dislocation: Displacement from the normal position of bones meeting at a joint.
Dysarthria: Difficulty in articulating words due to emotional stress or to paralysis, lack of
coordination, or spasticity of the muscles used in speaking.
Excoriation: A circumscribed removal of the epidermis of skin or mucous membrane.
Flexibility: Represents the relative ranges of motion allowed at a joint.

112

Focal injury: Acute and/or chronic injuries to the brain, including the cerebral
hemispheres, cerebellum, and brain stem.
Force: A push or a pull; the product of mass and acceleration.
Fracture: Breakage of a bone, either complete or incomplete.
Gadd Severity Index (GSI): An index developed to quantifying the severity of an injury
sustained in an automobile accident.
Glial fibrillary acidic protein: Is a cell-specific marker that, during the development of
the central nervous system, distinguishes astrocytes from other glial cells.
Halstead-Reitan Neuropsychological Test Battery: Consists of a series of individual
neuropsychological measures that, in combination, permit a skilled examiner to make
detailed inferences about the integrity of the cerebral hemispheres.
Head-contact injuries: An injury associated with direct trauma to the head.
Head Injury Criteria (HIC): Is a measure of the likelihood of head injury arising from an
impact.
Head-movement injuries: An injury associated with sudden changes in direction,
resulting in indirect trauma to the head.
Impact height: In the current study, defined as the height of the lateral malleolus of the
kicking foot when the foot makes contact with the Hybrid III female dummy head target.
Injury criteria: A mathematical relationship between some measurable physical
parameter interacting with a test subject and the occurrence of injury that directly results
from that interaction.
Injury rate: The incidence of injury per unit of athlete time.
Injury: Damage, wound, trauma.

113

Inverse dynamics: Use of link-segment models to represent mechanical behavior of
connected pendulums, or more concretely, body segments of humans.
Ischemia: is a condition that occurs when blood flow and oxygen are kept from a
particular part of the body.
Kinematics: The branch of mechanics concerned with motion without reference to force
or mass.
Kinetics: The branch of mechanics concerned with forces that cause motions of bodies.
Laceration: A tear in the flesh producing a wound with irregular edges.
Limited contact sports: A sport in which the rules are designed to prevent intentional or
unintentional contact between players which, if it occurs, carries strong penalties.
Linear acceleration: The rate of change in linear velocity over time.
Linear velocity: The rate of change in position over time.
Lipid peroxidation: Is a mechanism of cellular injury in plants and animals, used as an
indicator of oxidative stress in cells and tissues.
Neurofilament light polypeptide: Is a gene that provides instructions for making the
smallest protein component (the light subunit) of neurofilaments.
Non-contact sports: A sport in which the players are physically separated such as to make
it nearly impossible for them to make physical contact during the course of a game.
Non-collision sports: A sport in which the athletes are not permitted to hit or collide with
each other.
Outclassed rule: A referee in an amateur boxing has the responsibility to stop a fight at
any time one fighter seems in danger due to being clearly outmatched.

114

Pace auditory serial addition task: Is a test often used to measure attention,
concentration, working memory, and speed of information processing.
Pathomechanics: The study of mechanical forces that are applied to a living organism
and adversely change the body's structure and function.
Player-seasons: An injury incidence density rate that considers one-athlete participation
in a season.
Severity Index (SI): See Gadd Severity Index.
Second Impact Syndrome (SIS): Results from an acute, usually fatal brain swelling that
occurs when a second concussion is sustained before complete recovery from a previous
concussion.
Sitting height: Height of the participant while sitting on a bench with hips and back
against a wall, measured from the bench to the vertex of the head.
Shoulder height: Height of participant’s right shoulder while standing erect.
Skill level (colored belt, black belt): Individual skill levels in martial arts that follows a
colored belt system, where a light color belt indicates beginner/intermediate levels, and a
black belt is recognized as an advanced level. A participant that has not achieved a black
belt typically has a level of experience in martial arts less than 6 months to approximately
2 years. A black belt requires years of training, and it is usually reached within 2 years of
practice.
Sparring ready stance: Stance assumed by martial arts competitors during a free sparring
contest, characterized by a staggered anterior-posterior placement of the feet, with the
body weight evenly distributed on both feet, and a relatively high center of gravity.

115

Sprain: Ligamentous injury to a joint with possible rupture, but without dislocation or
fracture.
Standing height: Height of a participant when standing erect.
Strain: Excessive stretching or working of a muscle resulting in pain and swelling of the
tissue.
Symbol Digits Modality Test (SDMT): Detects cognitive impairment. The test involves a
simple substitution task that normal children and adults can easily perform.
Tau: Is a protein used as a serum marker of brain damage in mild traumatic brain injury.
Total kicking time: Starts from the moment the kicking foot leaves the ground, through
the contact with the target, and ends when the foot touches the ground again.
Trochanteric height: Height of a participant’s right trochanter from the ground while
standing.
Leg length: Measurement from the ground to the lateral condyle of the tibia while the
participant stands erect.
Wechler Intelligence Scale for Children III (WISC-III): A test developed to measure
intelligence in children ages 6-0 to 16-11.
Wide Range of Assessment Memory and Learning (WRAML): A test designed to assess
memory and learning functions across the school years.
Wound: An injury to the body (as from violence, accident, or surgery) that typically
involves laceration or breaking of a membrane (as the skin) and usually damage to
underlying tissues.

116

Appendix H
Permission Letter to Use Figure 7

April 26, 2011

Nate Dau
818 W. Hancock
Detroit, MI 48201USA

Dear Nate:
I am completing a doctoral dissertation at Michigan State University entitled
“Accelerations of a Hybrid III Dummy Head Resulting from Roundhouse Kick Impacts
and their Implications for Concussions in Boys and Girls”. I would like your permission
to reprint in my dissertation the following picture:

The requested permission extends to any future revisions and editions of my
dissertation, including non-exclusive world rights in all languages, and to the prospective
publication of my dissertation by ProQuest Information and Learning (ProQuest) through
its UMI® Dissertation Publishing business. ProQuest may produce and sell copies of my
dissertation on demand and may make my dissertation available for free internet

117

download at my request. These rights will in no way restrict republication of the material
in any other form by you or by others authorized by you. Your signing of this letter will
also confirm that you own [or your company owns] the copyright to the above-described
material.
If these arrangements meet with your approval, I would appreciate your assistance
by signing the letter where indicated below and return it to me via fax, email or regular
mail.
Thank you very much.
Sincerely,

Miguel Narvaez
1C Butler Gym
Saint Bonaventure University
Saint Bonaventure, NY 14778
Telephone (716)375-2233
Fax (716)375-2360
Email: mnarvaez@sbu.edu

PERMISSION GRANTED FOR THE USE REQUESTED ABOVE:
________________________________
[Type name of addressee below signature line]
Date:____________________________

118

Appendix I
Permission Letter to Use Figures 8 & 9

April 26, 2011
Diversified Technical Systems, Inc.
909 Electric Avenue, Suite 206
Seal Beach, CA 90740 USA
Dear Sir/Madame:
I am completing a doctoral dissertation at Michigan State University entitled
“Accelerations of a Hybrid III Dummy Head Resulting from Roundhouse Kick Impacts
and their Implications for Concussions in Boys and Girls”. I would like your permission
to reprint in my dissertation the following pictures:
a) TDAS PRO sensor input module, included in the TDAS PRO manual, downloaded
from:
http://dtsweb.com/library/tdas/DTS%20Datasheet%20TDAS%20PRO%20SIM6.2010.pdf

b) TDAS control software screen shot, included in the TDAS PRO manual, downloaded
from:

http://dtsweb.com/library/tdas/DTS%20Datasheet%20TDAS%20PRO%20SIM-

6.2010.pdf

119

The requested permission extends to any future revisions and editions of my
dissertation, including non-exclusive world rights in all languages, and to the prospective
publication of my dissertation by ProQuest Information and Learning (ProQuest) through
its UMI® Dissertation Publishing business. ProQuest may produce and sell copies of my
dissertation on demand and may make my dissertation available for free internet
download at my request. These rights will in no way restrict republication of the material
in any other form by you or by others authorized by you. Your signing of this letter will
also confirm that you own [or your company owns] the copyright to the above-described
material.

120

If these arrangements meet with your approval, I would appreciate your assistance
by signing the letter where indicated below and return it to me via fax, email or regular
mail.
Thank you very much.
Sincerely,
Miguel Narvaez
1C Butler Gym
Saint Bonaventure University
Saint Bonaventure, NY 14778
Telephone (716)375-2233
Fax (716)375-2360
Email: mnarvaez@sbu.edu
PERMISSION GRANTED FOR THE USE REQUESTED ABOVE:
________________________________
[Type name of addressee below signature line]
Date:____________________________

121

REFERENCES

122

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-Committee on Medical Aspects of Automotive Safety. (1971). Rating the severity of
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-Covassin, T., Swanik, C.B. & Sachs, M.L. (2003a). Epidemiological considerations of
concussions among intercollegiate athletes. Applied Neuropsychology, 10(1), 12-22.

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-Dau, N., Chien, H.C, Sherman, D. & Bir, C. (2006) Effectiveness of boxing headgear for
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Proceedings
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