ChiroACCESS Article



Sports Injuries and Stretching



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January 4, 2010

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Watching the Olympic Games and other international sports venues demonstrates the global use of pre-competition warm-up and stretching exercises by athletes.  Athletic trainers often assist athletes in their stretching routines.  The expected benefits of stretching include increased flexibility and injury prevention.  Often common beliefs and practices conflict with the scientific evidence and this is true to some extent with stretching.  Although the use of stretching does provide some temporary increase in flexibility, the literature suggests that overall it does not help prevent sports injuries.  As stated in a 2008 systematic review of the literature, “There is moderate to strong evidence that routine application of static stretching does not reduce overall injury rates.”

Furthermore, if stretching is used, it should be used consistently...Furthermore, if stretching is used, it should be used consistently because “There is an abundance of literature demonstrating that a single bout of stretching acutely impairs muscle strength, with a lesser effect on power.” There is also a concern over how much stretching is necessary and at what point it may be harmful.  Chiropractors engaged in sports medicine should be well aware of the biomechanical risks that ligamentous laxity and an unstable joint can present.  Some studies suggest that joint instability can be created through overstretching.

“Overall, the evidence suggests that increasing range of motion beyond function through stretching is not beneficial and can actually cause injury and decrease performance. These findings should be used to challenge common warm-up practices in athletics.” 

The December 2009 study below suggests that stretching has no effects on reducing overuse injuries but may reduce the incidence of muscle strain.  Other studies indicate that the value or possible adverse effects of stretching is dependent upon the nature of the sport.  Athletes engaged in high intensity sports like football and soccer might derive a benefit where those participating in low intensity sports like swimming and jogging may not.

The bottom line with respect to stretching is that it is far less beneficial than most seem to believe, has potential adverse effects with respect to athletic performance and can pose a risk factor for injury rather than injury prevention.  Virtually all scientists that are currently publishing in this field discuss the need for additional research.

There is far less controversy with respect to warm ups before exercise or sports competition.  A 2006 review of the literature noted that “Five studies, all of high quality (7-9 (mean=8) out of 11) reported sufficient data (quality score>7) on the effects of warming up on reducing injury risk in humans.”

To stretch or not to stretch: the role of stretching in injury prevention and performance.

Scand J Med Sci Sports. 2009 Dec 18. [Epub ahead of print]

McHugh MP, Cosgrave CH.
Nicholas Institute of Sports Medicine and Athletic Trauma, Lenox Hill Hospital, New York, New York, USA.

Stretching is commonly practiced before sports participation; however, effects on subsequent performance and injury prevention are not well understood. There is an abundance of literature demonstrating that a single bout of stretching acutely impairs muscle strength, with a lesser effect on power. The extent to which these effects are apparent when stretching is combined with other aspects of a pre-participation warm-up, such as practice drills and low intensity dynamic exercises, is not known. With respect to the effect of pre-participation stretching on injury prevention a limited number of studies of varying quality have shown mixed results. A general consensus is that stretching in addition to warm-up does not affect the incidence of overuse injuries. There is evidence that pre-participation stretching reduces the incidence of muscle strains but there is clearly a need for further work. Future prospective randomized studies should use stretching interventions that are effective at decreasing passive resistance to stretch and assess effects on subsequent injury incidence in sports with a high prevalence of muscle strains.

Does warming up prevent injury in sport? The evidence from randomised controlled trials?

J Sci Med Sport. 2006 Jun;9(3):214-20. Epub 2006 May 6.

Fradkin AJ, Gabbe BJ, Cameron PA.
Department of Epidemiology and Preventive Medicine, Monash University, Central and Eastern Clinical School, Alfred Hospital, Commercial Road, Melbourne, Vic. 3004, Australia.

BACKGROUND: The practice of warming up prior to exercise is advocated in injury prevention programs, but this is based on limited clinical evidence. It is hypothesised that warming up will reduce the number of injuries sustained during physical activity.

METHODS: A systematic review was undertaken. Relevant studies were identified by searching Medline (1966-April 2005), SPORTDiscus (1966-April 2005) and PubMed (1966-April 2005). This review included randomised controlled trials that investigated the effects of warming up on injury risk. Studies were included only if the subjects were human, and only if they utilised other activities than simply stretching. Studies reported in languages other than English were not included. The quality of included studies was assessed independently by two assessors.

RESULTS: Five studies, all of high quality (7-9 (mean=8) out of 11) reported sufficient data (quality score>7) on the effects of warming up on reducing injury risk in humans. Three of the studies found that performing a warm-up prior to performance significantly reduced the injury risk, and the other two studies found that warming up was not effective in significantly reducing the number of injuries.

CONCLUSIONS: There is insufficient evidence to endorse or discontinue routine warm-up prior to physical activity to prevent injury among sports participants. However, the weight of evidence is in favour of a decreased risk of injury. Further well-conducted randomised controlled trials are needed to determine the role of warming up prior to exercise in relation to injury prevention.

Stretching and injury prevention: an obscure relationship.

Sports Med. 2004;34(7):443-9.

Witvrouw E, Mahieu N, Danneels L, McNair P.
Department of Rehabilitation Sciences and Physical Therapy, Faculty of Medicine and Health Sciences, Ghent University, Belgium. erik.witvrouw@UGent.be

It is generally accepted that increasing the flexibility of a muscle-tendon unit promotes better performances and decreases the number of injuries. Stretching exercises are regularly included in warm-up and cooling-down exercises; however, contradictory findings have been reported in the literature. Several authors have suggested that stretching has a beneficial effect on injury prevention. In contrast, clinical evidence suggesting that stretching before exercise does not prevent injuries has also been reported. Apparently, no scientifically based prescription for stretching exercises exists and no conclusive statements can be made about the relationship of stretching and athletic injuries. Stretching recommendations are clouded by misconceptions and conflicting research reports. We believe that part of these contradictions can be explained by considering the type of sports activity in which an individual is participating. Sports involving bouncing and jumping activities with a high intensity of stretch-shortening cycles (SSCs) [e.g. soccer and football] require a muscle-tendon unit that is compliant enough to store and release the high amount of elastic energy that benefits performance in such sports. If the participants of these sports have an insufficient compliant muscle-tendon unit, the demands in energy absorption and release may rapidly exceed the capacity of the muscle-tendon unit. This may lead to an increased risk for injury of this structure. Consequently, the rationale for injury prevention in these sports is to increase the compliance of the muscle-tendon unit. Recent studies have shown that stretching programmes can significantly influence the viscosity of the tendon and make it significantly more compliant, and when a sport demands SSCs of high intensity, stretching may be important for injury prevention. This conjecture is in agreement with the available scientific clinical evidence from these types of sports activities. In contrast, when the type of sports activity contains low-intensity, or limited SSCs (e.g. jogging, cycling and swimming) there is no need for a very compliant muscle-tendon unit since most of its power generation is a consequence of active (contractile) muscle work that needs to be directly transferred (by the tendon) to the articular system to generate motion. Therefore, stretching (and thus making the tendon more compliant) may not be advantageous. This conjecture is supported by the literature, where strong evidence exists that stretching has no beneficial effect on injury prevention in these sports. If this point of view is used when examining research findings concerning stretching and injuries, the reasons for the contrasting findings in the literature are in many instances resolved.

Does stretching improve performance? A systematic and critical review of the literature.

Clin J Sport Med. 2004 Sep;14(5):267-73.

Shrier I.
Centre for Clinical Epidemiology and Community Studies, SMBD-Jewish General Hospital, Montreal, Quebec, Canada. ian.shrier@mcgill.ca

OBJECTIVE: The purpose of this article was to evaluate the clinical and basic science evidence surrounding the hypothesis that stretching improves performance.

DATA SOURCES AND SELECTION: MEDLINE and Sport Discus were searched using MeSH and textwords for English-language and French-language articles related to stretching and performance (or performance tests). Additional references were reviewed from the bibliographies and from citation searches on key articles. All articles related to stretching and performance (or performance tests) were reviewed.

MAIN RESULTS: Of the 23 articles examining the effects of an acute bout of stretching, 22 articles suggested that there was no benefit for the outcomes isometric force, isokinetic torque, or jumping height. There was 1 article that suggested improved running economy. Of 4 articles examining running speed, 1 suggested that stretching was beneficial, 1 suggested that it was detrimental, and 2 had equivocal results. Of the 9 studies examining the effects of regular stretching, 7 suggested that it was beneficial, and the 2 showing no effect examined only the performance test of running economy. There were none that suggested that it was detrimental.

CONCLUSIONS: An acute bout of stretching does not improve force or jump height, and the results for running speed are contradictory. Regular stretching improves force, jump height, and speed, although there is no evidence that it improves running economy.

A systematic review into the efficacy of static stretching as part of a warm-up for the prevention of exercise-related injury.

Res Sports Med. 2008;16(3):213-31.

Small K, Mc Naughton L, Matthews M.
Department of Sport, Health and Exercise Science, University of Hull, Hull, England.

A systematic review of the literature was undertaken to assess the efficacy of static stretching as part of the warm-up for the prevention of exercise-related injuries. Computer-aided literature search for articles post-1990 and pre-January 2008 related to static stretching and injury prevention using MEDLINE, SPORT Discus, PubMed, and ScienceDirect databases. All relevant randomised clinical trials (RCTs) and controlled clinical trials (CCTs) satisfying inclusion/exclusion criteria were evaluated by methodological assessment to score the studies using accredited criteria. Seven out of 364 studies met the inclusion/exclusion criteria. All four RCTs concluded that static stretching was ineffective in reducing the incidence of exercise-related injury, and only one of the three CCTs concluded that static stretching did reduce the incidence of exercise-related injury. Three out of the seven studies noted significant reductions in musculotendinous and ligament injuries following a static stretching protocol despite nonsignificant reductions in the all-injury risk. All RCTs scored over 50 points (maximum possible score = 100), whereas all CCTs scored under 45 points. There is moderate to strong evidence that routine application of static stretching does not reduce overall injury rates. There is preliminary evidence, however, that static stretching may reduce musculotendinous injuries.

The role of flexibility in injury prevention and athletic performance: have we stretched the truth?

Minn Med. 2003 May;86(5):58-61.

Ingraham SJ.
University of Minnesota, USA.

The use of stretching to prevent injury, off-set muscle soreness, and improve performance has been widely accepted and promoted in sports. However, little or no scientific evidence supports the practice, and recent research suggests that stretching, which increases flexibility beyond that needed for sport-specific movements, may cause injury. This article presents studies that have looked at the effects of stretching on injury and performance. Many earlier studies that showed benefits of stretching did not look at the effects of stretching alone; they also involved general cardiovascular workouts in the experimental but not control groups. More recent research shows that general fitness, rather than stretching, is a more important risk factor in injury prevention. This article also discusses studies of the relationship between joint laxity and injury and the role that stiffness may play in enhancing performance and preventing injury. Overall, the evidence suggests that increasing range of motion beyond function through stretching is not beneficial and can actually cause injury and decrease performance. These findings should be used to challenge common warm-up practices in athletics.

[Is stretching for sports performance still useful? A review of the literature]

Rev Med Suisse. 2005 Jul 27;1(28):1830-4.

[Article in French]

Gremion G.
Hôpital orthopédique de la Suisse romande, Swiss Medical Olympic Center, Rue Pierre Decker 4, 1005 Lausanne.

Since 1980, according to several authors, it is accepted that increasing flexibility of a muscle-tendon unit allows a better performance and decreases sports injuries. Stretching is regularly included in warm-up and in cooling-down. However, there are contradictory findings in the literature. In contrast, since 1990, there's evidence suggesting that stretching not only does not prevent injuries, but can also decrease the level of performance. Some part of these contradictions can be explained by the various sports activities. Those requesting an increased flexibility, such as gymnastic, dancing or diving, necessitate pre-exercise stretching to optimize the level of performance. In contrary, for sports with slow stretch-shortening cycle such as jogging or cycling, there is no scientific data showing a positive effect of stretching.

Stretching before exercise does not reduce the risk of local muscle injury: a critical review of the clinical and basic science literature.

Clin J Sport Med. 1999 Oct;9(4):221-7.

Shrier I.
Centre for Clinical Epidemiology and Community Studies, SMBD-Jewish General Hospital, Montreal, Quebec, Canada.

OBJECTIVE: To evaluate the clinical and basic science evidence surrounding the hypothesis that stretching immediately before exercise prevents injury.

DATA SOURCES AND SELECTION: MEDLINE was searched using MEDLINE subject headings (MeSH) and textwords for English- and French-language articles related to stretching and muscle injury. Additional references were reviewed from the bibliographies, and from citation searches on key articles. All articles related to stretching and injury or pathophysiology of muscle injury were reviewed. Clinical articles without a control group were excluded.

RESULTS: Three (all prospective) of the four clinical articles that suggested stretching was beneficial included a cointervention of warm-up. The fourth study (cross-sectional) found stretching was associated with less groin/buttock problems in cyclists, but only in women. There were five studies suggesting no difference in injury rates between stretchers and nonstretchers (3 prospective, 2 cross-sectional) and three suggesting stretching was detrimental (all cross-sectional). The review of the basic science literature suggested five reasons why stretching before exercise would not prevent injuries. First, in animals, immobilization or heating-induced increases in muscle compliance cause tissues to rupture more easily. Second, stretching before exercise should have no effect for activities in which excessive muscle length is not an issue (e.g., jogging). Third, stretching won't affect muscle compliance during eccentric activity, when most strains are believed to occur. Fourth, stretching can produce damage at the cytoskeleton level. Fifth, stretching appears to mask muscle pain in humans.

CONCLUSION: The basic science literature supports the epidemiologic evidence that stretching before exercise does not reduce the risk of injury.
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