This is the ACSM's stand on stretching.
Contrary to popular belief, stretching before a workout does not appear to decrease the occurrence of injury. The risk of injury seems to be about equal for those who stretch and those who do not stretch before exercise. The warm-up, not stretching, seems to be the important deterrent for injury, performed before an exercise bout. Stretching seems to offer more long term benefit such as maintaining functional flexibility and correcting particular muscular imbalances.
Shrier's (1999) review of the literature found three articles that suggested stretching was beneficial included a co-intervention of warm-up. One study found stretching was associated with less groin/buttock problems in cyclists, but only in women. Five studies suggesting no difference in injury rates between stretchers and non-stretchers and three suggesting stretching was detrimental. One reason stretching is thought to be ineffective in reducing the risk of injury is the fact that most muscle injuries occur when the muscle is eccentrically contracted within the normal range of motion (Shrier 1999). It seems more flexible individuals do not necessarily have less incidence of injury (Gleim 1997). In some cases those with greater flexibility may actually experience more injury, particularly if the excessive flexibility compromises joint integrity (Surberg 1983; Jones 1997). Although excessive flexibility may contribute to joint laxity, flexibility and joint integrity are not necessarily mutually exclusive. It may be possible for a joint to posses a combination of exceptional flexibility and excellent joint integrity.
Greater flexibility may impair performance in sports that that do not require a high degree of flexibility such as running. Runners with less flexibility are actually more efficient at running (Jones 2002). Intense static stretching may also reduce maximum force production. The loss of voluntary strength and muscular power may last up to one hour after the static stretch (Evetovich 2003, Young 2003). People who participate in activities that require more than average flexibility (eg: gymnasts, dancers, figure skaters) may still find stretching beneficial to their performance.
The ACSM recommends flexibility training a minimum 2 to 3 days per week holding each stretch for 10 to 30 seconds to mild discomfort; 3 to 4 repetitions per stretch. On a PNF stretches ACSM suggests a contract 6 seconds followed by a 10 to 30 second assisted stretch.
McCallister et. al. (2004) found that longer recovery days between stretching seemed to enhance stand and reach measurements:
Rest (hours) Stand & Reach (cm)
24 4.2
48 4.8
96 6.9
This data suggests it may not be necessary to stretch daily but instead take a few days recovery between sessions.
Although stretching does not seem to offer many short term benefits when performed before exercise, stretching does seem to offer other long term benefits. Improved flexibility may help prevent back and other orthopedic problems. Individuals with certain muscular imbalances or postural problems can benefits from stretching. Stretching can help maintain flexibility which may otherwise decline with age or inactivity due to an injury. Stretching may be more safely performed after exercise, when muscles are warm. Unless an activity requires extreme flexibility, stretching before is probably unnecessary. And even then, stretches should be performed after a warmup.
