Pre-Exercise Stretching Is Killing Your Workout

Oct. 10, 2010— -- Seems that most everything your high school gym teacher told you is wrong. Well, at least when it comes to all that start-of-the-class stretching.

A recent spate of studies shows that when it comes to warming up before exercising, phys ed instructors didn't do us any favors by having us to go through a series of calf extensions, hurdler's stretches and the like.

The latest salvo against stretching comes from a study published in the September issue of the Journal of Strength and Conditioning Research, which found that static stretching before a workout lowered runners' endurance and made their body less efficient. While previous studies have illustrated the effects of stretching on anaerobic activities, this was the first one to show the effects on runners.

The study took 10 fit middle- and long-distance runners (all male) and had each of them do the same run on two separate days with a 72-hour recovery period in between. The researchers divided the run into two 30-minute parts, with the first testing for caloric expenditure and the second assessing endurance. One day a participant did a stretching routine before running; on the other, he simply sat quietly prior to his workout.

During the first interval, participants ran at 65 percent of their VO2 max, keeping a constant pace. The researchers found that when the runners stretched before the workout, they burned, on average, 5 percent more calories during the run than when they didn't stretch.

Because they burned more energy to run the same distance it indicates their bodies performed less efficiently after stretching. For the second half, participants were told to run as far as they could on the treadmill for 30 minutes. When the runners didn't stretch, they went 3.4 percent farther than when they did.

Despite the rising tide of evidence that discredits the benefits of static stretching, the perception remains that it's necessary to do prior to working out. "Just asking runners, they seem to think stretching would enhance performance," said study co-author Jacob Wilson, an assistant professor of exercise science and sports studies at the University of Tampa. "The thought is that if you can loosen up and you feel looser, you can perform better."

But looser isn't better. "When you're lifting a weight, most of the damage comes when you're lengthening the muscle, and it's similar when you're stretching," Wilson said. "You're stretching the muscle and you do get microtearing and you're making the muscle less stiff too, so you're not able to store and utilize energy as well."