FRIDAY, Sept. 24, 2004 (HealthDayNews) -- Your gym teacher might have been wrong about the importance of limbering up.
Jumping on a bandwagon of previous research, a Canadian researcher reports that stretching before exercise might do more harm than good on the performance front.
According to an analysis of nearly two dozen studies, "acute" stretching before an athletic activity appears to hurt performance. On the other hand, the researcher found that regular programs of stretching may actually help athletes perform better.
Ultimately, however, the jury is still out on the ultimate value of stretching before exercise, said Dr. Julie Gilchrist, a medical epidemiologist with the U.S. Centers for Disease Control and Prevention, who co-wrote a report about stretching earlier this year. "The conclusive studies haven't been done," she said. "That final step just hasn't been made."
In the new report, Dr. Ian Shrier, a sports physiologist at Sir Mortimer B. Davis Jewish Hospital in Montreal, analyzed a series of studies about stretching. This kind of "meta-analysis" is often done when studies are too small in themselves to prove much. But when viewed together, "you're able to put them together and determine things that might not be obvious," Gilchrist explained.
Shrier reports his findings in the September/October issue of the Clinical Journal of Sport Medicine.
Conventional wisdom suggests stretching improves both performance and resistance to injury by promoting flexibility. But nearly all the 23 reviewed studies of "acute" stretching -- right before exercise -- found reductions in performance. Athletes had less power and weren't able to jump as high or as fast. One study showed improvement in "running economy," meaning the bodies of athletes handled the stress of running more effectively; four studies on running speed were contradictory.
But a program of "regular stretching" seemed to be beneficial. Seven of nine studies of regular stretching found it improves performance in areas related to the muscles after days or weeks, suggesting that stretching strengthened them. The remaining two studies found no effect of stretching.
In the CDC report, researchers looked at whether stretching helps prevent injuries. Their review of six studies didn't provide evidence that stretching is helpful, but more research is necessary, Gilchrist said.
It's also not clear if some athletes need more flexibility than others, she said. "A diver or a gymnast may need different amounts of flexibility than someone who's a football or soccer player."
But researchers are certain of one thing: Too much or too little flexibility can lead to injury, she said. To maintain flexibility, "stretching definitely plays a role. The question is when and how to work it into your routine. We don't have good answer for that yet."
What to do? One expert suggests that athletes not "throw the baby out with the bathwater" and neglect stretching. "Joggers are going to read this and think they don't need to stretch," said Lynn Millar, a professor of physical therapy at Andrews University in Berrien Springs, Mich.
"There's a lot of anecdotal reasons why we should be doing a stretch as part of the warm-up before an activity," Millar said. But she cautioned that stretching "is not the [entire] warm-up. It's part of the warm-up."
More information
Get details about exercise and stretching from the Nicholas Institute of Sports Medicine and Athletic Trauma.
