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Australasian Epidemiologist August 2015 Vol. 22.1
14
Round Table
Epidemiology of injuries in full-contact combat sports
Reidar P Lystad
School of Medical and Applied Sciences, Central Queensland University, Australia
Email: r.lystad@cqu.edu.au
Abstract
As in any sport, there is an inherent risk of injury to
practitioners of combative martial arts. Notwit hstanding the
potential for injury, there has not been a concerted eor t to
clearly elucidate the injury problem in full-contact combat
sports. The purpose of this review is to provide an overview
of the injury incidence, injury pattern, and injury sever ity in
six popular and commonly practiced full-contact combat
sports. Data from a total of 47 observational studies suggest
that there is a significant injury problem in f ull-contact
combat sports generally. However, the injury incidence rates
and injury patterns vary considerably across dierent styles,
which most likely is a reflection of dierences in competition
rules. Very little is known about the act ual sever ity of injuries
in combat sports. Future studies are strongly encouraged to
adopt stronger study methodologies.
Introduction
The term combat sports can be used to refer to the subset of
martial ar ts that are practiced for the purpose of competition.
Combat sports typically involve one-on-one combat, either
unarmed or wit h the use of various weapons such as sticks
(e.g. arnis, kali, eskrima), wooden swords (e.g. kendo), small
swords (e.g. modern fencing), or even lances (e.g. jousting).
Unarmed combat sports can be fur ther subdivided into
stri king styles (e.g. boxing, kickboxing, karate, taekwondo),
grappling styles (e.g. wrestling, judo, Brazilian jiu-jitsu), or
hybrid styles combining striking and grappling (e.g. mixed
martial ar ts). Naturally, there is a wide range of rulesets
across the combat sports. These rulesets regulate various
aspects of the contests, for instance: which techniques and
targets are permissible, what protective gear (if any) the
contestants must wear, and whether contests are won by
scoring more points or by disabling an opponent. Reflecting
the amount of force that can be used on an opponent,
combat sports can be divided into light-contact, medium-
contact, and full-contact variants.
Although bot h karate and taekwondo each boast having
almost 100 million practitioners worldwide, it is dicult to
estimate exactly how many people participate in combat
sports worldwide, and, moreover, to ascertain which of them
are the most popular or commonly practised. The ocial
program for the Rio 2016 Olympic Games includes three
unarmed combat sports, namely boxing, judo, and
taekwondo. Noteworthy among the non-Olympic combat
sports is mixed martial arts. Promoters and organisers of
mixed martial arts contests have enjoyed a surging
popularity and widespread coverage in mainstream media
since the early 2000s, but the sport has also at tracted rebuke
from both politicians and medical associations that wish to
see it banned.1
The health benefits of regular physical activity are
undisputed, and the speci fic health benefits of martial arts
practice have been reviewed elsewhere.2-4 However,
participation in sport and active recreation are not without
risk, and injuries can be an adverse outcome. Indeed, sport
injury is identified as a major public health problem,5-7 and
approximately 8% of youths discontinue sporting activ ities
annually because of injury.8 As in any sport, there is an
inherent r isk of injury to practitioners of combative mart ial
arts, in particular in f ull-contact combat sports. The aim of
any sport, therefore, should be to keep the risk of injury at an
acceptable level, and to ensure that t he benefits of
participation outweighs the potential adverse events.
It is been claimed that all styles of mar tial arts are safe and
that practitioners are seldom severely injured.9 However,
good quality evidence to support such claims are often
wanting. Moreover, there are good reasons to suspect that
the injury problem varies significantly between dierent
combat sports. Unlike in many other major sports such as
football, rugby, and basketball (to name but a few), there has
not been a long-standing, concerted eor t to clearly elucidate
the injury problem in popular combat sports. It is therefore
dicult to ascertain the true injury risk in these sports,
which in turn precludes athletes from making truly informed
choices. The lack of good quality epidemiological
investigations also precludes the identification of risk factors
that could become targets for injury prevention eor ts,
thereby improving the safety for combat sport athletes.
Fortunately, prospective epidemiological investigations of
injuries in combat sports have star ted to emerge in the
literature. It may therefore be useful to athletes and sport
governing bodies, as well as to sports injury prevention
Australasian Epidemiologist August 2015 Vol. 22.1
15
scientists, if the available data were synthesised in a way that
allowed for meaningful comparisons to be made. Thus, the
main objective of this review is to provide an overview of the
injury incidence, injury pattern, and injury severit y in six
popular and commonly practised full-contact combat sports
(i.e. boxing, kickboxing, judo, karate, taekwondo, and mixed
martial arts).
Methods
Selection criteria
Reports from obser vational studies published in peer-
reviewed literature were eligible for inclusion in this rev iew.
Eligible study designs included prospective or retrospective
cohort studies based on on-site competition injur y
surveillance data, and meta-analyses of similar data. On the
other hand, cross-sectional surveys, case-control studies,
case series and reports, commentaries, editorials, and letters
to the editor were excluded from th is review. Language
restrictions were applied such that only English, German,
French, and Spanish lang uage articles were included. Eligible
studies had to report epidemiological data such as incidence,
distribution, or severity of injuries in either boxing, judo,
karate, kickboxing, mixed martial ar ts, or taekwondo. No
studies were excluded based on sex, age, or any other
characteristics of the study population.
Search strategy
This review used a quasi-systematic approach to identify
relevant st udies. This entailed using the results from
previously conducted, sport-specific systematic literature
searches. Although t here are minor dierences between the
original search strategies (e.g. which databases were utilised,
when the searches were conducted, and which spor t-
specific keywords were used), they all included at a
minimum electronic searching of PubMed and
SPORTDiscus databases from inception to 2013. Moreover,
snowballing strategies were used to identif y additional
studies not captured by the original electronic searches.
Data extraction and analysis
Data from included studies were extracted and tabulated in
an electronic spreadsheet. The data of interest were as
follows: (i) injur y incidence rate per 1,000 athlete-exposures,
(ii) distribution of injuries by anatomical region and by type
of injury, and (iii) injury severity. One athlete-exposure was
defined as one athlete being exposed to the possibility of
incurring an injury while participating in a single contest
(fight or bout). If the included studies did not specifically
report injury incidence rates per 1,000 athletes-ex posures,
they were, if possible, calculated from the available data.
The number of injuries by anatomical region and by ty pe of
injury from individual studies were pooled for each combat
sport and presented as proportions of the total number of
injuries. In an attempt to increase the comparability across
the included studies, injuries were categorised according to
the Orchard Sports Injury Classification System, version 1010 ,
while unspecified injuries were omitted from the pooled
injury proportion calculations.
Similarly, the number of injuries by injur y severity were
presented as propor tions of the total number of injur ies.
Injury severit y was defined in accordance with previous
recommendations,11 that is, as the number of days elapsed
from the date of injury to the date of the athlete’s return to full
participation in training and match play. Injury severity was
categorised as follows: slight (0–1 days), minimal (2–3 days),
mild (4–7 days), moderate (8–28 days), severe (>28 days).
Results
A total of 47 observational studies were included in this
review. Two studies repor ted on injuries in both taekwondo
and judo. Thus, the total number of injury reports for each
combat sport were as follows: 13 for taekwondo12-24 , 3 for
kickboxing2 5-27, 5 for mixed mar tial arts28-3 2, 6 for boxing33-3 8,
13 for karate39-51, and 7 for judo.24, 51-56 In addition, t wo
meta-analyses (one for mixed martial arts1 and one for
taekwondo11) were identified and included in this review.
Injury incidence rates
Figure 1 shows the injury incidence rates per 1,000 athlete-
exposures as reported by the included studies. The small
circles represents point estimates from indiv idual
observational studies, while the large circles represent pooled
estimates from published meta-analyses. The data suggest
that, among the popular full-contact combat spor ts, t he risk
of injury is lowest in grappling styles such as judo (range:
41.2–115.1); greater in striking styles such as taek wondo
(range: 19.1–138.8), karate (range: 45.2–214.3), kickboxing
(range: 109.7–155.4), and boxing (range: 77.7–250.6); and
greatest in hybrid styles such as mixed martial arts (range:
85.1–2 80 .7 ).
Figure 1. Injury incidence rates per 1,000 athlete-
exposures in full-contact combat spor ts. Small squares
represent point estimates from individual obser vational
studies. Large circles represent pooled estimates from
published meta-analyses
0 50 100 150 200 250 300
Injury incidence rate per 1,000 athlete−exposures
Mi
xed martial arts
B
oxing
Ka
rate
Kickb
oxing
T
aekwondo
J
udo
Injury patterns
Figure 2 shows the proportions of the total number of injuries
by anatomical region across the included combat spor ts. T he
head and neck was the most frequently injured anatomical
region in boxing (84%), karate (74%), mixed mar tial arts (64%),
and kickboxing (55%); whereas the lower limb and upper
limb were the most frequently anatomical regions in
Australasian Epidemiologist August 2015 Vol. 22.1
16
taekwondo (51%) and judo (47%), respectively. The
proportion of trunk injuries was relatively small across
all combat spor ts (2–10%).
Figure 2. Proportions of total number of injuries by
anatomical region in full-contact combat sports
Proportion (%) of total number of injuries by anatomical region
Mi
xed martial arts
B
oxing
Ka
rate
Kickb
oxing
T
aekwondo
J
udo
Head and neck
Trunk
Upper limb
Lower limb
Figure 3 shows the proportions of the total number of injuries
by type of injur y across the included combat sports.
Contusion (which includes bruising and haematoma) was
found to be the most common type of injury in karate (55%),
taekwondo (45%), and kickboxing (40%); while laceration
(which includes abrasion) was the most common type of
injury in boxing (68%) and mixed mart ial ar ts (58%).
Compared to other combat sports, judo was found to have a
greater var iety of injury diagnoses, with joint sprain (31%)
being the most common type of injur y. Concussion
comprised a greater proportion of the total number of injuries
in kickboxing (19%) and boxing (14%) compared to taekwondo
(6%), MMA (4%), and karate (4%). The proportion of fractures,
however, was greater in mixed martial ar ts (27%) than in
taekwondo (8%), boxing (7%), kickboxing (7%), karate (4%), and
judo (2%).
Figure 3. Proportions of total number of injuries by type
of injury in full-contact combat sports
Proportion (%) of total number of injuries by type of injury
Mi
xed martial arts
B
oxing
Ka
rate
Kickb
oxing
T
aekwondo
J
udo
Contusion/Haematoma
Laceration/Abrasion
Joint sprain
Muscle strain
Fracture
Dislocation
Concussion
Other
Injury severity
Figure 4 shows the proportions of the total number of injuries
by injury severity across the included combat spor ts. Although
several of the included st udies mentioned injury severity, only
three of t hese measured injury severity in terms of actual, as
opposed to estimated, time-loss from participation. The
proportion of moderate to severe injuries (i.e. injuries resulting
in more than one week of time lost from play) was 32% in
taekwondo22 , 15% in karate50 , and 7% in judo.53 There were no
studies reporting on the severity of injur ies in boxing,
kickboxing, or mixed mar tial arts.
Figure 4. Proportions of total number of injuries by
injury severity in full-contact combat sports
Proportion (%) of total number of injuries by injury severity
Mi
xed martial arts
B
oxing
Ka
rate
Kickb
oxing
T
aekwondo
J
udo
?
?
?< 1 week
> 1 week
Discussion
This review highlights that there is a significant injury
problem in full-contact combat sports generally, that both
injury incidence rates and injury patterns vary considerably
across dierent styles, and t hat very little is known about the
actual severity of injuries in combat sports.
Among full-contact combat sports, t he risk of injur y appears
to be greater in hybrid styles (e.g. mixed mar tial arts),
intermediate in striking styles (e.g. boxing, kickboxing,
karate, and taekwondo), and lower in grappling styles (e.g.
judo), with injury incidence rates of around 230, 120, and 80
injuries per 1,000 athlete-exposures, respectively. However,
there is considerable heterogeneity in study met hodologies
among the included studies. For instance, the included
studies varied in terms of operational injur y and exposure
definitions, data collection methods, setting, and study
population characteristics. Consequently, there may have
been significant underreporting of injuries in some of the
included studies. It is therefore prudent to be cautious when
interpreting the injury incidence rates reported herein.
Furt hermore, all exposures are not equal. For instance, the
typical length of an exposure in most combat sports is
somewhere between 5 and 25 minutes, whereas matches in
team sports such as rugby and soccer may last an hour or
more. Thus, it becomes dicult compare the risk of injur y in
combat sports to other sports without first factoring in the
actual exposure time. Unfortunately, few studies on combat
sports report exposure time-adjusted injury incidence rates.
However, if we assume an average exposure time of 15
minutes, t hen we can estimate the time-adjusted injury
incidence rates for hybrid, striking, and grappling styles to be
approximately 920, 480, and 320 injuries per 1,000 contest-
hours, respectively. By this measure, the injur y risk in
full-contact combat sports is far greater than in popular
sports such as r ugby (80 per 1,000 match-hours)57, soccer
(20–25 per 1,000 match-hours)58, and running (8–18 per
1,000 hours).59 Although this measure provides a more direct
comparison, caution must nevertheless still be exercised
Australasian Epidemiologist August 2015 Vol. 22.1
17
because t here may be significant dierences in the total time
of competition exposure (e.g. annually or lifetime) that is
typical for combat sports and ot her spor ts such as rugby,
soccer, and running.
The included combat sports appear to have unique injur y
patterns, and dierences in competition rules undoubtedly
explain much of these observed variations in injury patterns.
For instance, lower limb injur ies are ver y uncommon in
boxing, but very common in taekwondo. Although it is not
permissible to strike the lower limb in either sport,
taekwondo allows using t he feet to kick the opponent’s trunk
or head. Another example is that head injuries are
uncommon in judo (which disallows strikes to the head), but
exceedingly common in boxing, kickboxing, mixed martial
arts and, to lesser extent, karate where strikes to the bare head
are allowed. The high propor tion of head injuries in some of
these combat sports is a cause for concern, especially
considering that continued repetitive head trauma (not
necessarily limited to clinically observable concussions) is
associated with degeneration in brain structures such as
thalamus, basal ganglia, and hippocampus, with measurable
decline in cognitive function.60
In regard to injury severity, only three of the included st udies
measured actual, as opposed to estimated, time lost to
participation in training or competition. With such scarcity
of data it becomes very dicult to both assess the act ual
burden injuries in combat sports, and, subsequently, to know
where to direct eorts to prevent or mitigate the risk of injury.
Thus, it is strongly recommended that future studies
investigate the sever ity of injuries in combat spor ts using
objective measurements of actual time lost to participation.
It is important to emphasise that this review has concerned
itself with competition injuries only. The injury problem is
expected, as is the case in many other sports, to be very
dierent in the training context, not only in terms of
incidence, but also in regard to injur y pattern and severity.
This disparity in injur y risk between training and
competition should be kept in mind when considering the
costs and benefits of participating in combat sports. It is, for
instance, both possible and reasonable to choose to train in
combat sports without ever participating in contests
or tournaments.
This review is limited by t he paucity of available injur y data
in some of the combat sports, as well as the methodological
quality of the included studies. It is possible the literature
searches failed to identify all relevant studies, while the
exclusion of articles in languages other than English,
German, Spanish, and Italian may have introduced language
bias. However, reviews of the potential impact of language
bias have concluded that language restrictions has generally
little eect on summar y on the overall findings.61 , 62 Lastly, the
included studies were not subjected to a formal risk of bias
assessment, which could, in turn, have been used to provide
preferential weighting when synthesising the data presented
in this review. The findings herein should be interpreted in
light of these limitations. To facilitate cross-study
comparisons, future studies are strongly encouraged to
adhere to the (STrengthening the Reporting of Obser vational
studies in Epidemiology (STROBE) Statement guidelines63 ,
adopt standard injury definitions, and employ standardised
sports injur y classification systems.
Conclusion
There is a significant injury problem in full-contact combat
sports. The risk of injury appears to be greatest in hybrid
styles (e.g. mixed martial arts), intermediate in striking styles
(e.g. boxing, kickboxing, karate, and taekwondo), and lowest
in grappling st yles (e.g. judo), with injury incidence rates
around 230, 120, and 80 injuries per 1,000 athlete-exposures,
respectively. The injury patterns vary considerably across
dierent styles, which most likely is a reflection of dierences
in competition rules. Unfort unately, very little is known
about the actual severity of injuries in combat sports.
Future studies are strongly encouraged to adopt stronger
study methodologies.
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