The Impact of Stretching on Sports Injury
Risk: A Systematic Review of the Literature
STEPHEN B. THACKER1, JULIE GILCHRIST2, DONNA F. STROUP3, and C. DEXTER KIMSEY, JR.3
1Epidemiology Program Office,2National Center for Injury Prevention and Control, and3National Center for Chronic
Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA
THACKER, S. B., J. GILCHRIST, D. F. STROUP, and C. D. KIMSEY, JR. The Impact of Stretching on Sports Injury Risk: A
Systematic Review of the Literature. Med. Sci. Sports Exerc., Vol. 36, No. 3, pp. 371–378, 2004. Purpose: We conducted a systematic
review to assess the evidence for the effectiveness of stretching as a tool to prevent injuries in sports and to make recommendations
for research and prevention. Methods: Without language limitations, we searched electronic data bases, including MEDLINE
(1966–2002), Current Contents (1997–2002), Biomedical Collection (1993–1999), the Cochrane Library, and SPORTDiscus, and then
identified citations from papers retrieved and contacted experts in the field. Meta-analysis was limited to randomized trials or cohort
studies for interventions that included stretching. Studies were excluded that lacked controls, in which stretching could not be assessed
independently, or where studies did not include subjects in sporting or fitness activities. All articles were screened initially by one
author. Six of 361 identified articles compared stretching with other methods to prevent injury. Data were abstracted by one author and
then reviewed independently by three others. Data quality was assessed independently by three authors using a previously standardized
instrument, and reviewers met to reconcile substantive differences in interpretation. We calculated weighted pooled odds ratios based
on an intention-to-treat analysis as well as subgroup analyses by quality score and study design. Results: Stretching was not
significantly associated with a reduction in total injuries (OR ? 0.93, CI 0.78–1.11) and similar findings were seen in the subgroup
analyses. Conclusion: There is not sufficient evidence to endorse or discontinue routine stretching before or after exercise to prevent
injury among competitive or recreational athletes. Further research, especially well-conducted randomized controlled trials, is urgently
needed to determine the proper role of stretching in sports. Key Words: ATHLETES, CONDITIONING, META-ANALYSIS,
therapists, and physicians recommend stretching in an effort
to both prevent injury and enhance performance; numerous
journal articles and textbooks are devoted to the topic,
providing a variety of approaches directed to different parts
of the body and for specific sporting activities (1). As more
people participate in sports and other recreational activities
through social changes (e.g., Title IX) and increased recog-
nition that physical activity is part of a healthy lifestyle,
injury prevention becomes more important. However, some
tretching before participation in athletic activities is
standard practice for all levels of sports, competitive
or recreational. Athletes, coaches, trainers, physio-
investigators have questioned the routine practice of stretch-
ing and contend that there is little evidence that stretching
pre- or postparticipation prevents injury and that it might
affect performance negatively (82,93). In particular, a recent
systematic review (35) concluded that the best available
evidence indicates that stretching before or after exercise
does not prevent muscle soreness or injury and that there is
insufficient evidence to assess effect on performance.
We developed a logic model to illustrate the relations
among stretching, flexibility, performance, and injury (Fig.
1). Flexibility is an intrinsic property of the body tissues that
determines the range of motion achievable without injury at
a joint or group of joints (40). There are several methods of
stretching to increase flexibility including passive, static,
isometric, ballistic, and proprioceptive neuromuscular facil-
itation (PNF) (Table 1). Although static stretching is the
easiest and most frequently used stretching method, each
approach has advocates (1). Both passive and PNF tech-
niques require a second person with specific skills, and there
is some concern that PNF techniques might increase the risk
of injury because of the resulting increase in stretch toler-
ance (i.e., the ability to increase the range of stretching
Address for correspondence: Stephen B. Thacker, M.D., M.Sc., Director,
Epidemiology Program Office, Centers for Disease Control and Prevention,
MS C08, Atlanta, GA 30333; E-mail: email@example.com.
Submitted for publication June 2003.
Accepted for publication October 2003.
MEDICINE & SCIENCE IN SPORTS & EXERCISE®
Copyright © 2004 by the American College of Sports Medicine
without pain). Concerns about connective tissue trauma
have caused the practice of ballistic stretching to fall from
Flexibility is dependent on the viscoelasticity of muscle,
ligaments, and other connective tissue. Flexibility is as-
sessed with tools such as goniometers to measure joint
angles, fleximeters to measure the degree of bending, and
arthrometers to measure joints. These tools are generally
used to measure static flexibility (i.e., the measured range of
motion about a joint or series of joints in an immobile
subject), and the relationship of these measures to dynamic
flexibility (i.e., the measure of resistance to active motion
about a joint or series of joints) is not clear (19). Although
some persons are described as loose-jointed, a general body
measure of flexibility has not been demonstrated, and there
is little agreement on the definition and limits of normal
flexibility (39). The improvement in short-term flexibility
that results from stretching has been documented (44).
As with stretching, little evidence exists that documents a
relation between increased flexibility and reduced incidence
of injury (54,55,88). Indeed, injury may be related to too
much or too little flexibility or, in some instances, increasing
flexibility may actually increase the rate of injury (49). The
lack of flexibility does not account for many muscle injuries
that occur within a normal range of motion (96). However,
an imbalance in flexibility in individual athletes might pre-
dispose to injury (54). Although stretching before activity
might improve performance for some sports that require an
increased range of motion (e.g., gymnastics or swimming),
increased flexibility might compromise muscle performance
for up to 1 h (56,57).
Literature reviews (87) and analytic studies (48,62,88)
concerning injury enumerate many risk factors such as age,
extremes in body mass index, decreased fitness, inexperi-
ence, short stature in women, increased body fat in men,
strength imbalance between flexor and extensor muscle
groups, history of previous injury, increased weekly running
mileage, increased duration and frequency of endurance
training, weight training, smoking, and competitive motiva-
tion. Yet, the studies have methodological problems, often
complicated by both ascertainment and information biases,
lacking sufficient statistical power and having inadequate
control of potential confounding variables such as warm-up.
In addition, most of the comparative analytic data on inju-
ries come from studies of runners. Close examination of
these studies, however, finds that stretching has not been
shown to prevent injury (61,87). Instead, use of stretching as
a prevention tool against sports injury has been based on
intuition and unsystematic observation rather than scientific
evidence. Indeed, risk factors are not often demonstrated
conclusively to predict injury because there is usually in-
sufficient epidemiologic evidence to make a judgment. Of
the few comparative studies in the literature, only a small
number address multiple potential risk factors and potential
confounding variables (49,62). Similarly, little research has
addressed stretching as an injury prevention strategy.
In this paper, we first conduct a systematic review of the
literature to summarize the research on flexibility and its
relation to stretching and sports injuries in the context of
other risk and protective factors. Second, we assess the
evidence for the effectiveness of stretching as a tool to
prevent injuries in sports. To do this, we first assess the
evidence that stretching improves flexibility as well as the
adverse effects of stretching on flexibility. We then examine
the effect on injury prevention of warm-up, a critical inter-
vening or independent variable, as well as other risk factors
for injury. Finally, we make recommendations for a system-
atic approach to future research and prevention.
Using OVID version 2, we searched electronic data bases:
MEDLINE, 1966 through August 2002; Current Contents,
1997 to August 2002; Biomedical Collection, 1993 to 1999;
and Dissertation Abstracts (in all languages) using MDCon-
sult and the following search terms: “stretching,” “flexibil-
ity,” “injury,” and “sports injury.” We searched without
language limitations. We limited this search using the terms
“epidemiology” and “injury prevention.” Using the same
strategy, we searched the Cochrane Library and SPORT-
Discus. We then identified additional citations from the
reference sections of papers retrieved and contacted experts
in the field to locate additional unpublished studies. We
performed a formal meta-analysis using only randomized
trials (RCT) or cohort studies for interventions that included
FIGURE 1—Logic model for relations among stretching, flexibility,
performance, and injury.
TABLE 1. Stretching methods.
PassiveSlow, sustained muscle lengthening with a partner
StaticSlow, sustained muscle lengthening held by subject for 15–60 s
Isometric Static stretching against an immobile force
Ballistic Rapid lengthening of the muscle by use of jerking or bouncing movements
PNF* Passive muscle lengthening with a partner after an antagonistic muscle is
* Proprioceptive neuromuscular facilitation.
Official Journal of the American College of Sports Medicinehttp://www.acsm-msse.org
stretching. We excluded studies that lacked controls, those
in which stretching could not be assessed independently of
other interventions, and those that did not include subjects in
sporting or fitness activities. All articles were screened by
one author (SBT). We identified 361 articles reporting about
flexibility (its underlying physiology and its relation to
stretching), risk factors for injury and methods for preven-
tion, alternative approaches to stretching, the effects of
stretching on performance and injury prevention, and ad-
verse effects of stretching and flexibility. Of these, six
reports compared stretching with other methods to prevent
We modified a scoring instrument previously used to
evaluate the methodological quality of cohort studies and
RCT (Fig. 2) (86). Reviewers were blinded to the primary
authors’ names and affiliations but not to the study results.
Each citation was then evaluated independently for quality
by three reviewers. After independent evaluation, the re-
viewers met to reconcile substantive differences in
We calculated pooled odds ratios based on an intention-
to-treat analysis using Epi Info Version 6 (31). We weighted
each study result by total study size and calculated both
crude and adjusted odds ratios (50). We conducted subgroup
analyses according to quality score (low vs high), nature of
intervention (single vs multiple muscle stretching), and
study design (RCT vs other). We calculated 95% confidence
intervals using the Mantel-Haenzel procedure. Because no
significant differences were found, we did not perform a
formal test for publication bias. However, given the nature
of our search, we are comfortable that no large comparative
study which shows a protective effect of stretching has been
completed. Heterogeneity was measured using the Q statis-
Stretching to improve flexibility. The literature on
flexibility includes both studies of the effects of stretching
on specific joints and muscles, and studies of the effective-
ness of alternative methods of stretching and the extent and
duration of the effect (Table 2). Alternative methods of
stretching, including passive stretching, static stretching,
ballistic stretching, isometric contractions, and PNF, have
been compared for their effects on flexibility (6,11,23). By
whatever method used to measure flexibility, in 27 reports
published since 1962, stretching was demonstrated to in-
crease joint flexibility about the knee (including hamstring/
quadriceps muscles) hip, trunk, and shoulder and ankle
joints (soleus/gastrocnemius muscles) (references available
from authors on request). Although there is evidence that
PNF stretching is more effective in improving flexibility
(2,22,41,74,89), this has not been demonstrated consistently
(10,29,33,60), and the apparent result might be related to
other factors such as posture during stretching (85). A 15-s
or 30-s passive stretch is more effective than shorter dura-
tion stretches (75,90) and as effective as stretches of longer
duration (4,63). Passive stretching is more effective than
dynamic stretching of the hamstring (5), although no dif-
ference was found in active versus passive stretching of the
hip joint (42). Various protocols have also been tested for
effectiveness such as timing of rest periods (9), placement
within a workout schedule (12), a stance phase stretch
versus a forward swing phase stretch (78), and repeated
passive stretching (30). The duration of increased flexibility
after stretching is from 6 to 90 min (17,68), although an
extensive program of several weeks duration has produced
increased flexibility that persists for several weeks (65,98).
Adverse effects of stretching/flexibility. There is
some evidence of unintended adverse effects of stretching
and/or increased flexibility. Stretching has been associated
with a temporary strength deficit (up to 1 h) (24,57) and
increased arterial blood pressure (13). Recent studies of
passive stretching shows significant adverse effects on jump
performance (14) and plantar flexion (65). Increased flexi-
bility decreases running economy (15,27) and peak perfor-
mance (77), but these findings are not consistent (28,58,70),
and there is some evidence that increased flexibility en-
hances performance (60).
Warm-up to prevent injury. Preparation for athletic
activity often includes both stretching and warm-up, making
it difficult to assess their independent effects on injury
FIGURE 2—Quality scoring form.
IMPACT OF STRETCHING ON SPORTS INJURY RISKMedicine & Science in Sports & Exercise?
prevention. Warm-up together with stretching increases the
flexibility of the ankle, hip, and knee joints (46,94) but has
not been shown to prevent muscle soreness (37). At least
one report demonstrates that static stretching and warm-up
by cycling increase flexibility equally for at least 15 min
(46), although the effects of combined intervention are not
consistent (76). Several programs that combine warm-up,
strength, and balance training with stretching have demon-
strated effectiveness in the prevention of knee and ankle
injuries (21,36,92), but the independent effects of warm-up
and stretching were not determined.
Since 1945, 32 published reports have addressed the
effect of warm-up on performance (references available
from authors on request). A summary of 22 clinical studies
in the 1950s and 1960s found that flexibility and perfor-
mance (especially strength and speed) in a number of sport-
ing activities improved after warm-up, especially when
stretching was vigorous, sustained, and related to the activ-
ity to be undertaken (71), and subsequent studies found
similar results. Passive methods to increase body tempera-
ture (hot baths, moist heat) also tended to increase perfor-
mance but to a lesser degree (69), whereas the effect of
massage on performance was not consistent (67). In this
literature, the detrimental effects on performance of fatigue
from vigorous activities suggests that there might be optimal
levels of warm-up, and that might, in turn, be related to the
fitness of the persons involved. A positive attitude toward
warm-up was associated with a significant improvement in
Risk factors for injury. Two different approaches ap-
pear in the literature to determine whether the lack of
flexibility puts athletes at risk for injury or whether stretch-
ing prevents injury. One approach is to examine flexibility
or stretching specifically to determine whether they are
associated with injury. A second approach uses cohort or
case-control methods, and flexibility and/or stretching are
among several risk or protective factors included in a mul-
Questionnaire surveys and/or personal logs of groups of
runners and other athletes have asked about stretching and
have shown either no association with injury (62,91), no
protective effect (95), or no increased injury rates (43).
Stretching after wrist hyperextension against weight de-
creased muscle soreness in college volunteers (18), but in
other studies, stretching before or after exercise had no
effect in the prevention of postexercise pain (47). Studies of
TABLE 2. Results of field studies to determine the effectiveness of stretching in the prevention of injuries.
Senior Author (Country)
Andrish et al. (US) (3)
PopulationStudy Groups Outcomes
2777 male navy midshipmen in 8
wk basic training
1) foam heel pad
2) heel stretching
3) heel pad and heel stretching
4) graduated running
97 with shin splints
1) 15/344 (4.4%)
2) 12/300 (4.0%)
3) 14/463 (3.0%)
4) 13/217 (6.0%)
5) 43/1,453 (3.0%)
27 with shin splints or tibial
1) 3rd quarter
a) total injuries 7
(0.3 per game)
b) sprains/strains 1
(0.04 per game)
2) a) total injuries 22
(0.8 per game)
b) sprains/strains 13
(0.46 per game)
1) 23 lower-extremity injuries
2) 25 lower-extremity injuries
Bixler and Jones (US)
5 Pennsylvania high school
football teams: 28 games
1) 3-min half-time warm-up/
stretch (3 teams)
2) controls (2 teams)
Pope et al. (Australia)
1998Randomized trial 1093 Army recruits in 26
platoons in 12-wk basic
1) 2, 20-s stretches of calf
before rigorous exercise (549
recruits in 13 platoons)
2) 2, 20-s stretches of wrist and
triceps before rigorous,
exercise (544 recruits in 13
1) 1995 season—static
stretching program—prior to
2) 1994 season-no stretching
Cross and Worrell (US)
195 college football players, 1994
and 1995 seasons
1) a) 153 injuries
b) 21 lower-extremity
2) a) 155 injuries
b) 43 lower-extremity
1) 25 lower-extremity overuse
2) 43 lower-extremity overuse
Hartig and Henderson
298 army recruits in two
1) 148 recruits—static
hamstring stretch, 3 times
2) 148 recruit controls—no
1) 735 recruits in 19 platoons,
20 second supervised
stretches of 6 major leg
muscle groups before each
physical training session
2) 803 recruits in 20 platoons—
no stretching Program
Pope et al. (Australia)
2000Randomized trial1538 army recruits in 39
platoons in 12-wk basic
1) 158 lower-limb injuries
2) 175 lower-limb injuries
Official Journal of the American College of Sports Medicinehttp://www.acsm-msse.org
flexibility or joint laxity have often shown no association
with injury (51,53), although the lack of flexibility (i.e.,
tightness) has been found to be associated with specific
injuries (20,66). A 1999 study of 303 male military trainees
found that the most flexible and the least flexible men were
at significantly increased risk of injury in a multivariate
Intervention studies. Six controlled studies have been
published that specifically address the role of stretching in
the prevention of injury (Table 2). Three of these studies
focused on stretching of specific muscle groups, either heel/
calf (3,72) or hamstring (32); the other three assessed pro-
grams that addressed multiple muscle groups (7,16,72).
Although two studies targeted the prevention of shin splints
(3) or shin splints and tibial stress reaction (7), the other four
studies examined all lower extremity injuries.
Pooled analysis of five of these studies found that stretch-
ing was not significantly associated with a reduction in total
injuries (OR ? 0.93, CI 0.78–1.11) (Table 3). (We were
unable to pool one study (7) because of the authors’ choice
of denominators for the rates (games rather than players).)
Although crude odds ratios were higher for low (2.36)
versus high quality studies (0.95), this difference did not
persist when adjusted odds ratios were calculated (0.88, CI
0.67–1.15 vs 0.97, CI 0.77–1.22). Weighted odds ratios
were also not significant for studies in which stretching
focused on specific muscles (0.80, CI 0.54–1.14) or multi-
ple muscle groups (0.96, CI 0.71–1.28). Further, odds ratios
for RCT (1.00, CI 0.81–1.25) and non-RCT (0.81, CI 0.61–
1.09) were similar. Tests for heterogeneity were not signif-
icant on any of these reported analyses.
Quality of reported studies. Quality scores for the
RCT ranged from 26 to 65 (of a possible 100) for the
individual rater scores; the median scores for the six studies
ranged from 29 to 61 (Table 2).
This review of the available evidence clearly demon-
strates that stretching of most if not all muscle groups that
are important to athletic performance will increase muscle
and joint flexibility, usually measured as short-term static
flexibility. Studies also suggest that extremes of inflexibility
and hyperflexibility increase the risk of injury. However, the
importance of these results for injury prevention within the
limits of normal flexibility is not documented in the litera-
ture. Because dynamic range of motion is generally greater
than static range of motion due to enhanced tissue elasticity
and reciprocal inhibition leading to relaxation of opposing
muscles during physical activity, the relevance of static
flexibility to dynamic performance is an unresolved issue
Qualitative flexibility is clearly important in sports such
as gymnastics, diving, ice skating, and dance. Also, flexi-
bility might improve performance under specific conditions
in other sports. At the same time, it is not clear whether there
is a flexibility threshold for optimal performance or that
additional flexibility in already flexible athletes is necessary
or desirable (49). Certainly, joint integrity should not be
compromised simply to increase range of motion. Although
some laboratory and clinical evidence suggests that in-
creased flexibility might improve athletic performance, little
population-based evidence addresses this issue. The best
available data indicate that performance might be lowered at
the extremes of flexibility and that, at least for some muscle/
joint groups, there might be optimal levels of flexibility that
would enhance performance. However, these benefits are
likely to be highly specific to a sport or even to a specific
Recently, the President’s Council for Physical Fitness and
Sports reported that stretching not only might not prevent
injuries but also might compromise performance (56). An-
imal studies also suggest that stretching does not protect
against acute injury (8). Muscle strain injuries occur during
eccentric exercise when muscles develop tension while
lengthening; fatigue and weakness make muscle more sus-
ceptible to injury (26). Several theories explain how perfor-
mance could be compromised or the rate of injury could be
unaffected or even increased because of stretching (82).
These theories include decrease in joint stability making
joint movement less efficient, increased tissue compliance
with a decrease in the ability of tendon and muscle tissue to
absorb energy leading to injury, creation of body positions
with dangerous loading effects that could stretch ligaments
too far, decreased strength before the recovery phase of
training, and increased pain tolerance leading to cytoskeletal
and tissue damage. Finally, because most injuries occur
during eccentric contractions within the normal range of
joint motion, it is not clear how increasing the range of
motion through stretching will decrease injury risk (82).
The limited epidemiological evidence more clearly ad-
dresses the question of injury prevention than its effects on
performance. The three RCT in this study that address
stretching and injuries fail to demonstrate a protective effect
of supervised stretching (3,72,73). The three cohort studies
(7,16,32) that find that stretching might prevent injury are
small and are of lower methodological quality than the
two recent RCT (72,73). Even pooling data from these
studies demonstrated no significant protective effect.
At the same time, the evidence is not of sufficient
strength, quality, and generalizability to recommend al-
tering or eliminating preexercise stretching. Further, no
studies have examined subpopulations that might be at
higher risk for injury (e.g., “tight” athletes) and thus
TABLE 3. Combined data from five prospective studies of the effectiveness of
stretching to reduce injury.
Andrish et al. (3)
Pope et al. (72)
Cross and Worrell (16)
Hartig and Henderson (32)
Pope et al. (73)
OR (with CI)
1.37 (0.67, 2.72)
0.91 (0.49, 1.68)
0.97 (0.70, 1.36)
0.50 (0.27, 0.90)
0.88 (0.77, 1.26)
Pooled Weighted OR0.93 (0.78, 1.11)
P ? 0.43
IMPACT OF STRETCHING ON SPORTS INJURY RISKMedicine & Science in Sports & Exercise?
might benefit from stretching. Finally, none of the studies
address the comparative severity of injury in experimen-
tal and control groups that could lead to an economic
reason for stretching if the injuries are less serious, as was
found for a workplace flexibility program (38).
Stronger evidence demonstrates that various approaches
to conditioning that include warm-up and stretching along
with other techniques such as strength training, plyometrics,
and proprioception training both enhance performance and
prevent certain kinds of injury (52,64,83,94). This suggests
that strength training, conditioning, and warm-up play an
important role in injury prevention. In addition, stretching of
specific muscles and joints for specific activities might
enhance the effectiveness of these other preexercise activi-
ties, an approach consistent with a multifactorial model for
prevention (97). At the same time, there might also be a risk
of injury and impaired performance associated with stretch-
ing without adequate conditioning and/or warm-up. Further
research on various stretching techniques targeting specific
joints and muscles is urgently required that will allow phy-
sicians, physical therapists, athletic trainers, coaches, and
personal trainers to make appropriate recommendations to
athletes. Too little is known to make evidence based
Some have argued that warm-up is more important than
stretching in the prevention of injuries in sports (79).
Warm-up increases blood flow to muscles, speed of nerve
impulses, oxygen and energy substrate delivery to working
muscle while removing waste products, and oxygen release
from hemoglobin and myoglobin; warm-up decreases both
the activation energy for cellular reactions and muscle vis-
cosity (59,81). These changes prepare the body for vigorous
exercise by accelerating metabolism in muscle fibers and
decreasing intramuscular resistance, thus increasing both
mechanical efficiency and range of motion (i.e., flexibility),
as well as the speed and force of muscle contraction. Animal
studies suggest that warm-up increases muscle elasticity,
which decreases the likelihood of muscle tearing (80).
Based on this review, we can recommend neither the
endorsement nor the discontinuation of stretching, which
has been a basic tenet of preparation for athletic participa-
tion. The evidence demonstrates that stretching clearly in-
creases flexibility and, to the degree that flexibility might
benefit performance or decrease the risk of injury, stretching
might be desirable. It is also evident that strength training,
conditioning, and warm-up have an important role in injury
prevention, and we suggest that when stretching is done, it
should be conducted in the context of adequate conditioning
and appropriate warm-up.
We recommend that several research questions be ad-
dressed in RCT. First, does preexercise stretching reduce the
occurrence of injury in well-conditioned competitive ath-
letes? Such studies should be done in a variety of sports/
activities and in both youth and adults of both sexes. Sec-
ond, does preexercise stretching reduce the occurrence of
injury in well-conditioned recreational athletes? Such stud-
ies should be done first in the most popular recreational
activities recommended currently for general better health
such as walking, running, swimming, and aerobics. Because
it might not be ethical to conduct RCT of this question
among poorly conditioned recreational athletes, one can
undertake cohort or other analytic studies in such popula-
tions to make recommendations for this potentially large
population at risk. In any of these studies, injury severity
and preparticipation conditioning and flexibility should be
measured and reported. Particular attention should be paid
to subjects with the least flexibility to determine whether
they might benefit most from stretching. Finally, because
athletes do not use injury prevention measures consistently,
the inherent behavioral aspects of sports injuries and issues
such as compliance and motivation warrant careful study (45).
Several methodologic issues are important in future re-
search. Blinded allocation of subjects and blinded data anal-
ysis for the original studies are necessary to minimize bias,
particularly in an area such as stretching where beliefs are
strongly ingrained. In RCT and cohort studies, subjects in
both intervention and control groups should be subject to
uniform, consistent, and ongoing monitoring of injuries and
performance. In calculating rates of injury, consideration
must be given to the choice of denominators (e.g., hours of
participation and number of participants vs numbers of
games), as well as baseline risk (e.g., fitness and previous
injury). Similarly, assessment of performance should exam-
ine the possibility of thresholds and optimal levels of flex-
ibility. More scrupulous attention to issues of bias (e.g.,
different baseline abilities of companies of military recruits)
and confounding (e.g., fitness and variable durations of
exercise) are critical to understanding the effect of stretch-
ing where so many other factors might play a part. Finally,
rigorous statistical methods are essential.
In conclusion, there is not sufficient evidence to endorse
or discontinue routine pre- or postevent stretching to prevent
injury among competitive or recreational athletes. Better
research is needed to determine the proper role of stretching
in sports, especially as there are increasing numbers of
athletes and growing recognition that all people need to
increase their physical activity to improve their health and
quality of life.
The authors thank Kenneth R. Powell for the idea of the logic
model and Robert Rowe, Joanna Taliano, and Antonia Blalark for
conducting the literature search.
Conflict of interest: The authors have no professional relation-
ships with companies or manufacturers who might benefit from the
results of the study. These results do not constitute endorsement of
any product by the authors or ACSM. The authors as employees of
the federal government and received no external funding for this
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