IF the first five to 10 minutes of your workout consists of stretching exercises to reduce the risk of injury, perhaps you should save yourself some time. Not only does such stretching fail to reduce the risk of injury, but recent studies have shown it also might hinder performance.
People who stretch before exercise have about the same risk of injury as those who don't, says epidemiologist Ian Shrier. Several years ago, Shrier reviewed half a dozen studies on the effects of stretching before exercise and found that not one demonstrated that it prevented injury. He published his findings in the Clinical Journal of Sport Medicine.
"At first people thought I was crazy," recalls Shrier, a physician at Sir Mortimer B. Davis Jewish General Hospital in Montreal. But his conclusions gained credence six months later, in August 2000, when Australian researchers published a large-scale study in the American College of Sports Medicine journal that reached the same conclusion.
That study involved 1,528 military recruits who followed the same exercise, weight and conditioning program. Half the recruits stretched before exercise; half didn't.
"A typical pre-exercise stretching protocol does not produce a clinically useful reduction in injury risk," wrote the authors. "If injury prevention is the primary objective, and the range of motion necessary for the sport is not extreme, the evidence suggests that athletes should drop the stretching before exercise and increase the warm-up."
Since then, pre-workout routines have started to change, with some up-to-date coaches de-emphasizing stretching and boosting warm-ups.
One reason that pre-workout stretches don't reduce injury, experts say, is because most exercise-related injuries are the result of overuse or improper training.
For example, says Shrier, doing calf stretches before you run doesn't benefit your leg muscles because they're never stretched in that extreme position while running. Almost all overuse injuries are strains that occur when the body is in the normal range of motion, he said.
Other sports injuries, such as muscle pulls and tears, occur as a result of muscle failure or weakness, not a lack of flexibility, researchers have found.
Thus strengthening deserves more attention, Shrier says. "When you're running and trip over a rock, what pulls you out of the injury is the muscle contracting. The stronger the muscle, the better it absorbs stress."
John DiFiori, chief of sports medicine at UCLA, agrees with the increasing evidence. "There's nothing convincing in the medical literature that proves stretching prevents injury."
To help prevent injury and re-injury, athletes and exercisers alike should emphasize strengthening instead, he adds.
Stretching before an event or game also might have an adverse effect on performance. "If you stretch before you exercise, you will see a decrease in your maximum effort," says Arnold Nelson, a professor of kinesiology at Louisiana State University who has studied the effects of acute stretching on performance.
Doing static stretches before exercise reduces the height of a jump by an average of three-fourths of an inch, possibly because it temporarily depletes the elasticity in the muscle, Nelson says. "Any player whose sport requires maximum output of the legs, including track, basketball and volleyball, should avoid stretching before their event or game if they want to achieve maximum performance."
Although you can skip the pre-workout stretches, don't throw out your yoga mat. Researchers still maintain that a good warm-up before exercise is vital, and that stretching -- at times other than before a big workout -- should remain part of an overall training and fitness regimen.
"Make no mistake, stretching at other times to promote overall flexibility is still a good idea," says Nelson. "It should be part of a good training program, but put it at the end of your activity when your muscles are warm."
Nelson and Shrier are quick to distinguish static-muscle stretching activities from warming up, which is still universally recommended.
Stretching involves putting muscles in extended positions and holding them there. Warming up involves using muscles in the way you plan to use them, but at a lower intensity, so you increase blood flow in the muscles and get them used to contracting in the way they'll need to for the exercise.
If you're going for a run, start at a slow jog. If you're playing basketball, toss a few easy balls into the net and dribble the ball around the court for a few minutes. Once you break a sweat, crank up the intensity.
"We know warming up improves performance; the evidence suggests it also prevents injury," says Shrier. "Whatever you do, don't stretch and skip the warm-up."
The findings are slowly catching on.
"It always takes a while for new ideas to trickle down from research labs to physician practitioners and ultimately to trainers," Shrier says. "Stretching before exercise is an entrenched notion. If you've been doing something for a long time, it's really hard to say you were wrong."
Irving "Boo" Schexnayder, a field and track coach at LSU, incorporates Nelson's findings into his coaching.
"I always had a gut feeling this was the case. I would see guys who stretched say they felt dead-legged afterward. Now I know why. I work at a school where someone is smart enough to figure this out and show me the data."
Though Schexnayder includes stretching in his athletes' training programs, he's careful of the amount and the timing. "It's like the old saying: Everything that makes you weaker in the short run, makes you stronger in the long run. Lifting a bunch of weights makes you tired and worn out right after the workout, but tomorrow, you'll be stronger for it."