The Impact of Stretching on Sports Injury Risk: A Systematic Review of the Literature
Review of studies looking at dynamic/static stretching and its impact on sports injury
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
Could not confirm if stretching reduces or increases injury, question is more subtle (too much or too little appear to be the issue).
Insights, lessons learnt:
- look more into studies of warm-up/warm-down - look more at the studies on optimal time for passive stretch (v. Useful!)
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. 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 predispose to injury (54). increased flexibility might compromise muscle performance for up to 1 h (56,57) By whatever method used to measure flexibility, in 27 reports published since 1962, stretching was demonstrated to increase 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). A 15-s or 30-s passive stretch is more effective than shorter duration 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 difference was found in active versus passive stretching of the hip joint (42). 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). Recent studies of passive stretching shows significant adverse effects on jump performance (14) and plantar flexion (65). Increased flexibility decreases running economy (15,27) and peak performance (77), but these findings are not consistent (28,58,70), and there is some evidence that increased flexibility enhances performance (60). Studies also suggest that extremes of inflexibility and hyperflexibility increase the risk of injury Certainly, joint integrity should not be compromised simply to increase range of motion Further, no studies have examined subpopulations that might be at higher risk for injury (e.g., “tight” athletes) and thus might benefit from stretching 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. 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 viscosity (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).