What your gym teacher never told you about stretching before exercise

It’s probably not worth your time

Photo by Pensiero/Flickr

You don’t need to look very far to find advice about stretching and exercise: the oft-cited wisdom is that they should go hand-in-hand, like peanut-butter and jelly or Bonnie and Clyde. You’ve surely heard that a little stretch before and/or after a work-out helps muscles warm up, keeps injuries at bay, and stress and muscle tension away.

Stretching also, apparently, maintains muscle strength. On the aptly named RunningInjuryFree.org blog, the writer claims, “stretching will help strengthen your muscles, enabling you to run better and helping you avoid injury.” The Globe and Mail, which has developed a love affair with running over the last year, has dedicated many column inches and even videos to stretching advice for active readers.

Yet, other mainstream news outlets have made much of studies that show stretching before running has no impact on injury. “Stretching before your run?” the Toronto Star asked smugly. “You’re wasting your time.”

So what are bendy (or brittle) Science-ish readers to make of this conflicting information?

The science shows you may want to think twice about dedicating time to the stretch. In a recent update of a systematic review about stretching to reduce muscle soreness, the investigators examined randomized or quasi-randomized studies of pre-exercise or post-exercise stretching techniques designed to prevent or treat muscle soreness and found that “muscle stretching, whether conducted before, after, or before and after exercise, does not produce clinically important reductions in delayed-onset muscle soreness in healthy adults.” In other words, stretching probably— not definitely—reduces soreness, but the effect is so small as to be barely noticeable. (This conclusion was the same as an earlier systematic review on the same subject.)

Another July 2011 Cochrane systematic review—“Interventions for preventing lower limb soft-tissue running injuries”—looked at the benefits of stretching for runners. It synthesized 25 trials, which included more than 30,000 participants from military recruits, to runners from the general population, to soccer referees and even prisoners. It stated, “Overall, the evidence base for the effectiveness of interventions to reduce soft-tissue injury after intensive running is very weak, with few trials at low risk of bias.” One of the authors of the study, Dr. Ella Yeung (PhD) of the Hong Kong Polytechnic University, told Science-ish, “There is no evidence to suggest that stretching has a protective effect toward running-related injuries.”

Was the time limber readers spent in pretzel-like positions all for naught? We called on one of the kings of stretching studies, Dr. Rob Herbert (PhD) of the George Institute for Global Health in Sydney, to find out. He has conducted two systematic reviews on stretching and exercise, including the first one mentioned in this column, as well as three randomized trials on the subject.

Dr. Herbert told Science-ish not to get “too hung up” about stretching. “If stretching does reduce injury risk and soreness, the effects are very small. If you like stretching, keep doing it because it might have a small beneficial effect (i.e., it might reduce injury risk and muscle soreness by a very small amount). If you don’t like stretching or don’t have time to do it, you’re probably not missing out on much by not stretching.”

Keep in mind, though, stretching may confer other health gains: Dr. Yeung said, “Perhaps there is some psychological benefit or improved circulation.” And stretching increases flexibility. But Dr. Herbert pointed out these are only “transient” increases, which last for minutes or hours after the stretch. “It is not so clear that stretching produces lasting increases in flexibility, although regular stretching clearly does increase tolerance to stretch. So if you think flexibility is of intrinsic value—I don’t—or if you like feeling flexible, regular stretching may be beneficial.”

Going forward, we need more “carefully conducted randomized studies investigating the effects of stretching on performance,” said Dr. Herbert. For now, dear readers, do what you like with your workout but don’t feel the need to bend like a Cirque du Soleil performer every time you’re at the gym just because your high-school gym teacher said you should.

Science-ish is a joint project of Maclean’s, The Medical Post, and the McMaster Health Forum. Julia Belluz is the associate editor at The Medical Post. Got a tip? Seen something that’s Science-ish? Message her at julia.belluz@medicalpost.rogers.com or on Twitter @juliaoftoronto

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