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The effectiveness of exercise interventions to prevent
sports injuries: a systematic review and meta-analysis
of randomised controlled trials
Jeppe Bo Lauersen,
1
Ditte Marie Bertelsen,
2
Lars Bo Andersen
3,4
▸Additional material is
published online only. To view
please visit the journal online
(http://dx.doi.org/10.1136/
bjsports-2013-092538).
1
Institute of Sports Medicine
Copenhagen, Bispebjerg
Hospital, Copenhagen NV,
Denmark
2
Faculty of Health and Medical
Sciences, Copenhagen N,
Denmark
3
Department of Exercise
Epidemiology, Institute of Sport
Sciences and Clinical
Biomechanics University of
Southern Denmark, Odense,
Denmark
4
Department of Sports
Medicine, Norwegian School of
Sport Sciences, Oslo, Norway
Correspondence to
Jeppe Bo Lauersen,
Institute of Sports Medicine
Copenhagen, Bispebjerg
Hospital, Building 8, 1. Floor,
Bispebjerg Bakke 23, 2400
Copenhagen NV, Sealand
2400, Denmark;
jeppelauersen@stud.ku.dk
Accepted 31 August 2013
Published Online First
7 October 2013
To cite: Lauersen JB,
Bertelsen DM, Andersen LB.
Br J Sports Med
2014;48:871–877.
ABSTRACT
Background Physical activity is important in both
prevention and treatment of many common diseases, but
sports injuries can pose serious problems.
Objective To determine whether physical activity
exercises can reduce sports injuries and perform stratified
analyses of strength training, stretching, proprioception and
combinations of these, and provide separate acute and
overuse injury estimates.
Material and methods PubMed, EMBASE, Web of
Science and SPORTDiscus were searched and yielded 3462
results. Two independent authors selected relevant
randomised, controlled trials and quality assessments were
conducted by all authors of this paper using the Cochrane
collaboration domain-based quality assessment tool.
Twelve studies that neglected to account for clustering
effects were adjusted. Quantitative analyses were
performed in STATAV.12 and sensitivity analysed by
intention-to-treat. Heterogeneity (I
2
) and publication bias
(Harbord’s small-study effects) were formally tested.
Results 25 trials, including 26 610 participants with
3464 injuries, were analysed. The overall effect estimate on
injury prevention was heterogeneous. Stratified exposure
analyses proved no beneficial effect for stretching (RR
0.963 (0.846–1.095)), whereas studies with multiple
exposures (RR 0.655 (0.520–0.826)), proprioception
training (RR 0.550 (0.347–0.869)), and strength training
(RR 0.315 (0.207–0.480)) showed a tendency towards
increasing effect. Both acute injuries (RR 0.647 (0.502–
0.836)) and overuse injuries (RR 0.527 (0.373–0.746))
could be reduced by physical activity programmes.
Intention-to-treat sensitivity analyses consistently revealed
even more robust effect estimates.
Conclusions Despite a few outlying studies, consistently
favourable estimates were obtained for all injury prevention
measures except for stretching. Strength training reduced
sports injuries to less than 1/3 and overuse injuries could
be almost halved.
INTRODUCTION
Increasing evidence exists, for all age groups, that
physical activity is important in both prevention and
treatment of some of the most sizable conditions of
our time,
1–3
including cardiovascular disease, dia-
betes, cancer, hypertension, obesity, osteoporosis,
and depression. Although overall population levels of
physical activity is a general concern, increasing levels
of leisure time physical activity and sports participa-
tion have been reported in some population groups.
4
Injuries are virtually the sole drawback of exercise,
but may be a common consequence of physical activ-
ity and have been shown to pose substantial pro-
blems.
5–7
Management of sports injuries is difficult,
time-consuming and expensive, both for the society
and for the individual.
8–10
However, sports injury
prevention by different kinds of strength training,
proprioception exercises, stretching activities, and
combinations of these, is accessible to essentially
everyone and requires limited medical staff assistance.
This adds several interesting aspects regarding the
potential dispersion, applicability, and compliance to
these programmes.
Most studies on musculoskeletal injuries have
focused on one particular intervention, injury type/
location, sport or studied other relatively narrowly
defined research questions. This applies to most
reviews and meta-analyses as well.
11–18
However,
Parkkari et al
19
described 16 controlled trials in a
narrative review. Central concepts of sports injury
prevention such as extrinsic (including exposures,
environment, equipment) and intrinsic (including
physical characteristics, fitness, ability, age, gender,
psychology) risk factors and the ‘sequence of preven-
tion’model of van Mechelen
20
were summarised.
Aaltonen et al
21
presented an overview of all sports
injury prevention measures, but as in the literature up
until their search in January 2006, the focus of this
review was primarily on extrinsic risk factors.
22
Recently, and with less restrictive exclusion criteria,
Schiff et al
23
covered the same topic with additional
studies. Aaltonen et al and Schiff et al were unable to
obtain full quantification of intervention effect esti-
mates. Steffen et al
24
presented a narrative review of
acute sports injury prevention written by field
experts for each location of injury, but an examin-
ation and quantification of specific training exposures
and a differentiation of acute and overuse outcome
effect estimates is still lacking.
This review and meta-analysis will broaden the
scope of previous reviews and meta-analyses on
sports injury prevention and focus on the preventive
effect of several different forms of physical activity
programmes and complement the existing summative
literature on extrinsic risk factor reduction. Valuable
summary literature exists for both neuromuscular
proprioception
14 15
and stretching exercises.
17 18
However, aggregation of effect estimates and com-
parison with the effect of strength training and an
intervention group with multiple exposures (combin-
ing ex strength, proprioception, stretch etc) could
reveal new and interesting information, enabling pro-
posals for future directions in the field of sports
injury prevention. This study consequently aimed at
performing stratified analyses of different injury pre-
vention exercise programmes and additionally pro-
vides separate effect estimates for acute and overuse
injuries.
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MATERIAL AND METHODS
Search strategy and study selection
A review protocol was composed, comprising a priori specifica-
tion of analyses, inclusion/exclusion criteria, injury definition
and search strategy. Injury was defined according to the
F-MARC consensus statement for football, merely broadened to
fit all forms of physical activity.
25
See online supplements
eMethods1–3 and eFigure 1 for full injury definition, detailed
search entries, study selection description and flow chart.
PubMed, EMBASE, Web of Science and SPORTDiscus databases
were searched to October 2012 with no publication date restric-
tions. The search was performed by four blocks of keywords
related to prevention, injury and diagnoses, sports, and rando-
mised controlled trials. The searches were customised to accom-
modate the layout and search methods of each search engine
and the application of additional free text words were based on
the coverage of subject terms. Reference lists of retrieved articles
were hand searched for trials of potential interest and the search
was later updated to January 2013.
Search results yielded 3462 hits, which were screened by title
to yield 90 titles. After exclusion by abstract, 40 were read in
full text and 22 were included. Another three studies were
included from reference lists and updated search. Study selec-
tion followed a priori-specified inclusion and exclusion criteria.
Inclusion criteria Exclusion criteria
▸Primary prevention
▸Free of injury at inclusion
▸Sports/physical activity injuries
▸Randomised controlled trials
▸Appropriate intervention/control
arms
▸Conducted in humans
▸Reported in English
▸Peer-reviewed publications
▸Influencing pathology
▸Surrogate measures of injury
▸Any use of devices (kinesiotaping,
insoles, etc)
▸Any means of transportation (bicycles,
motor driven, skies, equestrian, etc)
▸Inadequate follow-up
Two reviewers ( JBL and DMB) independently assessed the eli-
gibility criteria with subsequent consensus by discussion. If
unanimous consensus could not be reached, this was arbitrated
by a third person (LBA).
In total, 25 studies were included.
26–50
Data extraction
All included studies were assessed using the domain-based evalu-
ation tool recommended by the Cochrane collaboration.
51
Tw o
reviewers ( JBL and DMB) independently collected the support
for judgement and final judgements required consensus from all
authors of this paper. If reporting was inadequate or unclear,
efforts were made to contact the corresponding authors and ask
by ‘open questions’in order to reduce the risk of overly positive
answers. Weighting of studies by quality assessment was consid-
ered but not performed, as such appraisals would inevitably
involve subjective decisions and no evidence in support of this
approach exists.
51
Data extraction for total estimate and exposure subgroup esti-
mates covered the primary outcome, defined by each study.
Injuries were classified as acute or overuse according to defini-
tions used by each study and proprioception was defined as
exercises aiming at improving joint proprioception and/or joint
stability. For the outcome subgroups, acute and overuse injuries,
we additionally extracted appropriate secondary data from
studies where information was available in order to optimise the
power of these analyses. Overlapping entities were omitted so
no injury was analysed more than once.
The stratification of studies into less heterogeneous exposure
subgroups was, with the exception of Beijsterveldt et al,
27
per-
formed after completion of the literature search. Beijsterveldt
et al was added from the updated literature search and was
unambiguously fitted into the multiple exposures group.
As compliance plays a central role in the robustness of results,
sensitivity analyses without studies that neglected to analyse by
intention-to-treat were conducted.
During the iterative process of hypothesis generation and pre-
liminary searches the prespecified eligibility criteria were elabo-
rated but not changed. All a priori-specified analyses were
performed as planned.
Statistics
Whenever possible, only first-time injuries were taken into
account as repeated outcomes are likely to be dependent of each
other and therefore would introduce bias. Most studies have
analysed by calculation of either RR, injury rate RR or Cox
regression RR. When no appropriate effect estimates were
reported or studies neglected to adjust for clustering effects, we
adjusted for clustering effects and calculated a RR. Twelve
included studies were not originally adjusted for cluster random-
isation. As individuals in clusters potentially lack independence
of each other, a regulation of sample size calculations is often
required. The equation for cluster adjustment is
IF¼1þ(n1)r
where ρis the intracluster correlation coefficient, n the average
cluster size and IF the inflation factor. Effective sample size is
calculated by dividing sample size with IF.
52
The intracluster
correlation coefficient was calculated by
r¼s2
c=(s2
cþs2
w)
where s
2
w
is the within cluster variance of observations taken
from individuals in the same cluster and s
2
c
the variance of true
cluster means.
53
In the nine studies where the corresponding
authors did not provide us with sufficient data for ρcalculation,
we achieved this by calculating an average intracluster correl-
ation coefficient based on p values from studies, which were
appropriately adjusted for clustering effects.
In order to address reporting bias formally, we sought to test
all analyses by the Harbord small-study effect test with a modified
Galbraith plot.
54
This follows the recommendations by the
Cochrane handbook for systematic reviews of interventions and
is available in STATA V.12.
51 55
Effective sample sizes for interven-
tion and control group populations were used for the required
binary data input to achieve a cluster-adjusted result for this test.
The heterogeneity for all analyses was assessed by I
2
and the
χ
2
(Q) p value. I
2
is calculated from the Stata given Q value and
number of studies (n) by
I2¼Qðn1Þ
Q
A rough interpretation guide of I
2
has been proposed by
Higgins et al.
51
All analyses were computed in STATA V.12 by user-written
commands described by Egger et al
56
The random effects model
was used for the weighting of studies. Statistically heterogeneous
2 of 8 Lauersen JB, et al.Br J Sports Med 2014;48:871–877. doi:10.1136/bjsports-2013-092538
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estimates were graphically explored by the metainf command,
displaying the influence of each individual study on the effect
estimate. These analyses did not reveal conclusive information
of particular studies primarily causing the heterogeneity and
will not be reported throughout this article.
RESULTS
Study characteristics
Table 1 summarises the characteristics of 25 included studies. A
full study characteristics table is available in the online supple-
ments eTable 2. In total 26 610 individuals were included in the
analysis and effect estimates were based on 3464 injuries.
Thirteen studies were performed on adult participants, 11
studies on adolescents and one study included both.
We contacted nine authors and four supplied clarifying
answers with subsequent change in their data or quality
assessment. For detailed quality assessments and quality assess-
ment summary see online supplementary eMethods 4, eTable 1
and eFigure 2.
Total estimate
The total effect estimate was RR 0.632 (95% CI 0.533 to
0.750, I
2
=70% with a χ
2
p<0.001). Brushoj et al,
28
Eils
et al,
30
Gilchrist et al,
34
Holmich et al
36
and Soderman et al
46
did not report intention-to-treat data. When performing a sen-
sitivity analysis on the 20 studies with intention-to-treat data,
an estimate of RR 0.608 (0.503–0.736, I
2
=74%, χ
2
p<0.001)
was found. A post hoc analysis stratified for age showed RR
0.577 (0.453–0.736, I
2
=68%, χ
2
p<0.001) for adolescents
and RR 0.683 (0.526–0.885, I
2
=72%, p<0.001) for adults
(figure 1).
Table 1 Study characteristics summary
Study Intervention Population Completion Follow-up Injuries Primary out
Askling et al
26
Strength Soccer, male, elite Intervention 15 Control 15 10 weeks + 1
season
Intervention 3 Control 10 Hamstring injury
Beijsterveldt et al
27
Multi Soccer, 18–40, male
amateur
Intervention 223 Control 233 9 months Intervention 135 Control 139 All injuries
Brushoj et al
28
Multi Conscripts,
19–26 years
Intervention 487 Control 490 12 weeks Intervention 50 Control 48 Overuse knee injury
Coppack et al
29
Strength Recruits, 17–30 years Intervention 759 Control 743 14 weeks Intervention 10 Control 36 Overuse ant. knee
pain
Eils et al
30
Proprioception Basketball, 1st–7th
league
Intervention 81 Control 91 1 season Intervention 7 Control 21 Ankle injury
Emery et al
31
Proprioception Students, 14–19 years Intervention 60 Control 54 6 weeks +
6 months
Intervention 2 Control 10 All injuries
Emery and
Meeuwisse
32
Multi Soccer, 13–18 years Intervention 380 Control 364 1 year Intervention 50 Control 79 All injuries
Emery et al
33
Proprioception Basketball,
12–18 years
Intervention 494 Control 426 1 year Intervention 130 Control 141 All injuries
Gilchrist et al
34
Multi Soccer, collegiate Intervention 583 Control 852 12 weeks Intervention 2 Control 10 Non-contact ACL
Heidt et al
35
Proprioception H. school, female,
soccer
Intervention 42 Control 258 1 year Intervention 6 Control 87 All injuries
Holmich et al
36
Multi Football, 2nd–5th
level
Intervention 477 Control 430 42 weeks Intervention 23 Control 30 Groin injuries
Jamtvedt et al
37
Stretch Internet, >18 years Intervention 1079 Control 1046 12 weeks Intervention 339 Control 348 Lower limb + trunk
injury
LaBella et al
38
Multi Athletes, female Intervention 737 Control 755 1 season Intervention 50 Control 96 Lower extremity
injury
Longo et al
39
Multi Basketball, male Intervention 80 Control 41 9 months Intervention 14 Control 17 All injuries
McGuine and
Keene
40
Proprioception Basketball, adolescent Intervention 373 Control 392 4 weeks + 1
season
Intervention 23 Control 39 Ankle sprain
Olsen et al
41
Multi Handball, 15–17 years Intervention 958 Control 879 8 months Intervention 48 Control 81 Knee and ankle
injury
Pasanen et al
42
Multi Floorball, female, elite Intervention 256 Control 201 6 months Intervention 20 Control 52 Non-contact injuries
Petersen et al
43
Strength Soccer, male, elite Intervention 461 Control 481 12 months Intervention 12 Control 32 Hamstring injuries
Pope et al
44
Stretch Recruits, 17–35 years Intervention 549 Control 544 12 weeks Intervention 23 Control 25 4 specific LE injuries
Pope et al 2000
45
Stretch Recruits, male Intervention 666 Control 702 12 weeks Intervention 158 Control 175 Lower limb injuries
Soderman et al
46
Proprioception Soccer, female, elite Intervention 62 Control 78 7 months Intervention 28 Control 31 Lower extremity
injury
Soligard et al
47
Multi Football, 13–17,
female
Intervention 1055 Control 837 8 months Intervention 121 Control 143 Lower extremity
injury
Steffen et al
48
Multi Soccer, female Intervention 1073 Control 947 8 weeks + 1
season
Intervention 242 Control 241 All injuries
Walden et al
49
Strength Soccer, 12–17, female Intervention 2479 Control 2085 7 months Intervention 7 Control 14 ACL injuries
Wedderkopp et al
50
Proprioception Handball, 16–18,
female
Intervention 111 Control 126 10 months Intervention 11 Control 45 All injuries
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Stratified exposure analyses
The strength training estimate including four studies was RR
0.315 (0.207–0.480, I
2
=0%, χ
2
p=0.808). All studies in the
strength training group were analysed by intention-to-treat. For
stratified exposure Forest plots see online supplementary
eFigure 4–7.
The pooled effect estimate for six studies with propriocep-
tion training as the primary exposure showed a RR of 0.550
(0.347–0.869, I
2
=66%, χ
2
p=0.012). Sensitivity analysis of
intention-to-treat ruled out Eils et al
30
and Soderman et al
46
and revealed RR 0.480 (0.268–0.862, I
2
=71%, χ
2
p=0.017).
Unlike the above two exposures, the overall estimate
for stretching did not prove significant with RR 0.963
(0.846–1.095, I
2
=0%, χ
2
p=0.975) based on three studies.
All studies in the stretching group were analysed by
intention-to-treat.
The combined effect estimate for the 12 studies with multiple
exposure interventions revealed a RR of 0.655 (0.520–0.826,
I
2
=69%, χ
2
p<0.001). Sensitivity analysis of intention-to-treat
excluded Brushoj et al
28
Gilchrist et al
34
and Holmich et al
36
and revealed RR 0.625 (0.477–0.820, I
2
=75%, χ
2
p<0.001;
figure 2).
Stratified outcome analyses
On the basis of primary or secondary data from nine studies,
the RR for all types of exposures against acute injury was 0.647
(0.502–0.836, I
2
=73%, χ
2
p<0.001). One study had strength
training as exposure, two studies did proprioception training
and the remaining six studies were from the group of multiple
exposure studies. Sensitivity analysis of eight intention-to-treat
analysed studies (Soderman et al
46
was excluded) showed a RR
0.615 (0.470–0.803, I
2
=75%, χ
2
p<0.001).
Figure 1 Total estimate Forest plot.
Stretching studies are denoted by red,
proprioception exercises yellow,
strength training green, and multiple
component studies blue.
Figure 2 Exposure estimates Forest
plot. Stretching studies are denoted by
red, proprioception exercises yellow,
strength training green, and multiple
component studies blue.
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Six studies provided data on overuse injuries. RR from these
six studies was 0.527 (0.373–0.746, I
2
=19%, χ
2
p=0.287). All
studies in this analysis, except one proprioception training study,
were multiple exposure studies. All analysed studies reported
intention-to-treat data (figure 3A,B).
Small-study effect
The Harbord test for the total estimate of all 25 studies showed
a highly significant small-study effect test. Exposure and
outcome subgroups revealed significant test for only the mul-
tiple exposures group. See online supplementary eFigure 7 for
modified-Galbraith plot and online supplementary eTable 3 for
Harbord tests.
DISCUSSION
An overall RR estimate for physical activity for injury preven-
tion, adjusted for clustering effects, was 0.632 (0.532–0.750),
and slightly lower when sensitivity analysed by intention-to-treat
(RR 0.607 (0.501–0.735)). A preventive effect of this size
should be considered convincing, but the analysis was heteroge-
neous and the result is, therefore, clinically useless. However, it
also suggests that some types of interventions may prove better
than others.
Stretching did not show any protective effect (RR=0.961
(0.836–1.106)), while strength training proved highly significant
(RR 0.315 (0.207–0.480)). Results from stretching and strength
training studies were not heterogeneous despite different pro-
grammes were used and outcomes of interest were different. This
points towards a strong generalisability of results. Proprioception
training and multiple exposure programmes were also effective
(RR=0.480 (0.266–0.864) and 0.625 (0.477–0.820), respect-
ively), but results were relatively heterogeneous.
The effect estimate of stretching and proprioception training
analyses in this article corresponds to earlier reviews.
14 15 17 18
Our data do not support the use of stretching for injury preven-
tion purposes, neither before or after exercise, however it
Figure 3 (A) Acute outcomes
estimate Forest plot. Proprioception
studies are denoted by yellow, strength
training green, and multiple
component studies blue. (B) Overuse
outcomes estimate Forest plot.
Proprioception studies are denoted by
yellow and multiple component studies
blue.
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should be noted that this analysis only included two studies on
army recruits and one internet-based study on the general popu-
lation. Strength training showed a trend towards better prevent-
ive effect than proprioception training and proved significantly
better than multiple exposure studies, even though all multiple
exposure studies included a strength training component.
Further research of strength training for a wider range of injur-
ies is still needed, as our analyses suggest great sports injury pre-
vention potential for this type of intervention. With a growing
number of randomised controlled trials containing numerous
exposure types, it was of interest to assess intervention studies
with multiple exposures separately, although, as expected, still
being a heterogeneous subgroup. Though it makes intuitive
sense to design an array of exposures for prevention of all injur-
ies, it is important to note that each component may be reduced
quantitatively and/or qualitatively by doing so. Multiple expos-
ure programmes may therefore reduce the proportion of proven
beneficial exposures and consequently reduce the overall pre-
ventive effect on sports injury. Additionally, the risk of designing
too extensive prevention programmes will unavoidably be
enhanced with growing amounts of applied exposures and com-
pliance may suffer as a consequence. Although most multiple
intervention studies in this analysis were well designed and
carried out in a satisfactory way, this subgroup did not exhibit
an unambiguous preventive effect on sports injuries. Our find-
ings suggest that designs of multiple exposure interventions
should at least be built from well-proven single exposures and
that further research into single exposures remains pivotal.
When analyses were stratified by outcome, both acute (RR
0.615 (0.470–0.803)) and overuse (RR 0.527 (0.373–0.746))
injuries were effectively reduced by preventive physical activity,
although overuse injuries fared slightly better.
Five of six studies analysing overuse injuries were multiple
exposure studies, and estimates were not particularly heteroge-
neous. Six of nine studies analysing acute injuries were multiple
exposure studies with heterogeneous effect sizes. It is not pos-
sible to derive which parts of these interventions manifested the
preventive effect. Future studies should report acute and
overuse injuries separately and test specific exposures against
these in order to acquire further knowledge in this import area.
Strengths and limitations
The aim of this meta-analysis was to aggregate a wide array of
populations, exposures and outcomes to augment the external
validity while maintaining the suitability of combining studies.
Physical activity is broadly defined and populations include
army recruits, recreational and professional athletes. In this
regard, it should be pointed out that the diversity of included
studies should not be interchanged with the I
2
measure of statis-
tical heterogeneity, which exclusively concerns inconsistency in
effect sizes. The statistically homogeneous analyses of strength
training and stretching studies differing in population, interven-
tion, and outcome, prove the generalisability of results. The stat-
istically heterogeneous analyses of this meta-analysis should be
interpreted with caution as this heterogeneity could arise from
true variation (diversity in design) and/or artefactual variation
(bias by conduct, attrition, etc).
Omission of intention-to-treat analysis and cluster adjustment
are two sources of potentially serious bias. As compliance to
intervention programmes appears to vary and remains a dis-
puted phenomenon, the analysis by intention-to-treat plays a
central role in the robustness of results.
57–61
In the present
meta-analysis we extracted data from intention-to-treat analyses
whenever possible and performed sensitivity analysis by
exclusion of five studies with no report of intention-to-treat ana-
lysis. Contrary to the expected more conservative effect esti-
mate, the intention-to-treat sensitivity analyses revealed even
more beneficial effect estimates. As a result we can conclude
that physical activity as primary prevention against sports injur-
ies is effective, even if it has been argued that compliance issues
could diminish the implementation and effect of these pro-
grammes. We speculate the above to result from an association
between using intention-to-treat analysis and study conduct in
general. For example, Brushoj et al
28
added concurrent training
in the critical high risk period of military training initiation,
which intuitively appears detrimental to overuse injuries.
Soderman et al
46
exhibited several methodological issues and
reported adverse effects of major injuries that have not been
reproduced by other studies. None of them analysed by
intention-to-treat and exclusion of such studies improved the
quality of included studies and subsequently the effect estimate.
Cluster adjustment is similarly important in order not to over-
estimate the power of the study. A strength of this meta-analysis
is the adjustment of these studies that report the same effect esti-
mate but underestimate the width of CIs. Corresponding
authors of studies without cluster adjustment were contacted
and three provided data for ρcalculation. For the remaining
nine studies we calculated an average p value extracted from 12
reported values of 10 studies that performed correct adjustment
methods. This caused, in some cases, a dramatic, down-
regulation of effective sample size which affected the study
weight in the quantitative analyses.
A short discussion of the allocation concealment and partici-
pant blinding quality assessments is advocated. As true partici-
pant blinding is frequently argued to be impossible in sports
injury prevention and allocation, concealment makes less sense
in non-pharmacological interventions, these quality assessment
items should be interpreted with caution. In spite of this, some
of the included studies made qualified efforts to alleviate these,
which, in this review, resulted in a lower risk of bias judgement.
The domain-based tool was chosen as evaluation tool of this
review as recommended by the Cochrane collaboration with the
most convincing validation evidence in this area. Although not
being perfectly suited for assessment of sports injury prevention
studies, assessment of these parameters still holds relevance as
these factors can greatly influence analyses.
62 63
A Harbord’s small-study effect test and a modified Galbraith’s
plot were performed for this meta-analysis to assess publication
bias. The small-study effect test for the total estimate was highly
significant, while the multiple exposures subgroup was the only
subgroup showing a statistically significant test. According to
Egger et al
64 65
significant small-study effects may arise from a
number of reasons, including true publication bias, heterogen-
eity, chance, and methodological differences between smaller
and larger studies. As the p value of the small-study effects
increased when the total estimate test was divided into less het-
erogeneous subgroups, it is likely that a substantial part of the
total estimate small-study effect originates in heterogeneity.
Owing to the relatively heavy burden of implementing physical
activity interventions, it should be noted that smaller studies
often would be able to pay greater attention to the intervention
for each team/individual, thereby enabling them to obtain more
thorough intervention quality. Hence, a methodological differ-
ence may exist as well.
CONCLUSION
In general, physical activity was shown to effectively reduce
sports injuries. Stretching proved no beneficial effect, whereas
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multiple exposure programmes, proprioception training, and
strength training, in that order, showed a tendency towards
increasing effect. Strength training reduced sports injuries to less
than one-third. We advocate that multiple exposure interven-
tions should be constructed on the basis of well-proven single
exposures and that further research into single exposures, par-
ticularly strength training, remains crucial. Both acute and
overuse injuries could be significantly reduced, overuse injuries
by almost a half. Apart from a few outlying studies, consistently
favourable estimates were obtained for all injury prevention
measures except for stretching.
What this study adds
This meta-analysis provides quantitative effect estimates of
different exercise programmes on sports injury prevention.
Comparison of exposures reveals a highly effective strength
training estimate, significantly better than multicomponent
studies.
Acknowledgements The authors would like to thank Thor Einar Andersen,
associate professor, Department of Sport Medicine, Norwegian School of Sport
Sciences and Ashley Cooper, professor, Centre for Exercise, Nutrition and Health
Sciences, University of Bristol for comments and manuscript revision.
Contributors All authors of this paper have contributed substantially to conception
and design, analysis and interpretation of the data, drafting the article or revising it
critically for important intellectual content and final approval of the version to be
published.
Competing interests None.
Provenance and peer review Not commissioned; externally peer reviewed.
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doi: 10.1136/bjsports-2013-092538
7, 2013 2014 48: 871-877 originally published online OctoberBr J Sports Med
Jeppe Bo Lauersen, Ditte Marie Bertelsen and Lars Bo Andersen
controlled trials
review and meta-analysis of randomised
to prevent sports injuries: a systematic
The effectiveness of exercise interventions
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