Runners do it before a race. Swimmers do it before hopping in the pool. Your average gym rat does it before starting to pump iron. Most coaches, gym teachers, and personal trainers preach that stretching before exercise is an essential part of both avoiding injury and improving performance. But while it’s still popularly considered a basic tenet of health and wellness, scientific research into the value of stretching has cast doubt on its usefulness. For many athletic pursuits, studies suggest that stretching might actually be detrimental.
Even for those who follow fitness science closely, old habits die hard and many may be loath to give up stretching. “Because stretching decreases pain and makes you feel good, it is easy to extrapolate this to think it will prevent injury. But unfortunately, the reason it makes you feel good is one of the reasons it does not prevent injury,” states Dr. Ian Shrier, a sports medicine physician at McGill University in Montreal and author of many scientific studies on stretching.
So how did stretching become so ingrained in our collective athletic consciousness to begin with?
The case for stretching as a means for injury prevention is grounded in the theory that a muscle that has been lengthened by stretching is more supple, decreasing stress to surrounding tendons, ligaments, and muscles and protecting them from the repeated stresses of activity. A study in the journal Sports Medicine advises that “improving flexibility through stretching is another important preparatory activity that has been advocated to improve physical performance. Maintaining good flexibility also aids in the prevention of injuries to the musculoskeletal system.”
Unfortunately, there is at best a tenuous connection between stretching and injury risk. “In general, stretching before exercise does not prevent injury,” Shrier says. “But we have not yet studied every possible context, so some people argue that it might still be beneficial for particular activities based on some theories.”
The question is not whether stretching actually results in a short-term increase in a person’s flexibility—it does—but whether that state confers protection against injury.
The most common mode of stretching, and the type that has come under fire, is referred to as static stretching. It involves lengthening a muscle and holding it in a mildly uncomfortable position, usually for somewhere between 15 and 60 seconds.
In activities with a high risk of overuse injuries, such as jogging or cycling, research has concluded that this kind of stretching really doesn’t lessen the chance of injury. Research presented in the British Journal of Sports Medicine concluded that there wasn’t any evidence to suggest that a stretching intervention was effective in preventing lower limb injuries in joggers. The same article even advised swimmers, who habitually stretch their shoulders and arms before exercise, to minimize stretching, particularly at the shoulders where excessive mobility can cause injury.
Some of the pushback against static stretching also comes from the concern that any roadblock to activity—like the time it takes to get a good pre-exercise stretch—makes some less likely to exercise. The time spent dutifully stretching before exercise could detract from another more potentially useful activity, like a good warm-up, strength training, or stability exercises.
While pre-exercise stretching has come into question, stretching outside of exercise does seem to have some value, especially as aging decreases flexibility. Flexibility generally describes the range of motion commonly present in a joint. Although stretching can enhance flexibility, it’s an attribute that decreases with age, and varies by gender and ethnic group.
But being more flexible is not always better. “There’s certainly such a thing as too much flexibility,” says Sage Rountree, author of The Runner’s Guide to Yoga. “We need only enough to move through a healthy range of motion—beyond that, we can strain muscles and tendons and even destabilize ligaments and compromise joint health.”
Science has long known that the most flexible individuals are more likely to suffer injuries than an individual of average flexibility—one study of U.S. Army recruits found that those with the most and least flexibility more than doubled their risk of injury.