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If your clients are confused about the benefits of stretching, and when and how to stretch, they are not alone. Recent research suggesting that stretching before exercise does little good, and may even do harm, has many fitness professionals and researchers scratching their heads. While fitness professionals have advocated stretching before and after cardiovascular and strength-training exercise for decades, most of this advice has been based on intuition, rather than scientific research. Here are some recent research findings, with an explanation of how you may want to apply them in your work.

Stretching during warm-up

Stretching during the warm-up does not appear to prevent injury or muscle soreness. If stretching before exercise reduces risk of injury, we would expect to see lower injury rates in people who stretch before working out. However, numerous studies comparing groups of athletes who stretch during warm-up to those who do not have found no differences in the occurrence of injury. Risk of injury appears to be about equal for stretchers and non-stretchers. The same results have been found for muscles soreness: There is equal amounts of soreness in those who stretch and those who don't. One review 4 of the 12 best studies on pre-exercise stretching found that four studies suggested pre-exercise stretching reduced risk of injury; three studies found that stretching increased risk of injury; and five found no effect.

Many researchers now believe that, except for activities requiring extreme flexibility, stretching before exercise is probably unnecessary. The review of studies 4 pointed out that most muscle injuries occur while the muscle is contracting in the normal range of motion, so extending the range of motion through stretching would not be expected to help.

Flexibility does not seem to prevent injury

Flexibility requirements vary from sport to sport, but in general, more flexibility does not mean less injury. 2 In some studies, those with the greatest amount of flexibility actually experienced more injury, perhaps due to less stable joints. More flexibility may also impair performance in sports that do not use the extremes of a joint's range of motion, such as running. Runners with less flexibility are more efficient. Similarly, tight muscles perform better in powerlifting competitions.

Stretching before exercise

Stretching may reduce a muscle's maximal force production. Prolonged passive stretching decreases the maximal force production of muscle. This results in a decrease in voluntary strength for up to one hour after the stretch, partly because of slower muscle activation and lower contractile force. This may concern athletes who participate in sports that require maximal muscle force production, such as basketball, football, soccer, volleyball, and many track and field events.

This effect seems to be reversed when stretching is followed by a warm-up requiring submaximal contractions of the stretched muscles, such as jogging after stretching the calf muscles. The contractions seem to restore the muscle to its previous condition, and maximal force production does not seem to remain impaired.

Stretching may still be a good idea for some people. Despite the lack of evidence for pre-exercise stretching benefits, many people should still continue to stretch during warm-up routines. In particular, people who participate in activities that require greater-than-normal flexibility, such as dancers, gymnasts or figure skaters, may still find stretching beneficial to their performance. People who have used stretching to recover from an injury, and have become accustomed to stretching before exercise, may still wish to include stretching in their warm-up routines.

Warm-ups prevent injury and improve performance

Some people seem to equate stretching and warming up, but the two are not the same. While pre-exercise stretching does not appear to have a lot of benefit, a good warm-up does. A warm-up that mimics the movements that will occur during the workout improves flexibility, strength and agility, and reduces risk of injury. A warm-up should gradually increase in intensity, and continue until muscle temperature is elevated.

Stretching after a workout

Stretching after a workout -- or in a separate session -- feels good and can improve flexibility, which declines with age. Stretching appears to be most effective for increasing flexibility when done after, rather than before, a workout, when muscles are warm. However, although stretching before exercise does not appear to have very many short-term benefits, a lifetime of regular stretching can increase flexibility and slow the loss of flexibility that occurs with age. Improvements in flexibility may prevent back and other orthopedic problems, and may help maintain a joint's range of motion and improve quality of life in older adults.

Most group exercise instructors and personal trainers should still teach their clients good stretching exercises, and stress the importance of maintaining adequate flexibility. Classes that include plenty of stretching, such as tai chi and yoga, can also be a good way to improve flexibility. FM


REFERENCES

1. Bracko, M.R. Can stretching prior to exercise and sports improve performance and prevent injury? ACSM's Health & Fitness Journal 6 (5): 17-22, Sep./Oct. 2002.

2. Gleim, G.W., and M.P. McHugh. Flexibility and its effects on sports injury and performance. Sports Medicine 24 (5): 289-99, 1997.

3. Herbert, R.D., and M. Gabriel. Effects of stretching before and after exercising on muscle soreness and risk of injury: Systematic review. British Medical Journal 325 (7362): 468-470, 2002.

4. Shrier, I. Stretching before exercise does not reduce the risk of local muscle injury: A critical review of the clinical and basic science literature. Clinical Journal of Sport Medicine 9: 221-227, 1999.

Barbara A. Brehm, Ed.D., is professor of exercise and sports studies at Smith College, Northampton, Mass.




©Copyright 2006. Fitness Management

Article by Barbara A. Brehm, Ed.D.