After decades of fitness routines that began with lunges, toe-touches, and other stretches, the practice of static stretching before workouts has, in recent years, fallen out of favor.
Instead, driven by research suggesting that pre-exercise stretching can impair performance, many athletes now start with a warm-up followed by dynamic moves, like leg swings or drills that prepare them for the motions involved in their sport.
Now, a new review of studies adds nuance to the recommendations – as well as a reprieve for people who like the feel of a good stretch. There may be a place for static stretching after all, but only after a good warm-up and before dynamic stretching. Static stretching also appears to be most beneficial if done for short periods of time.
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"If you do around 60 seconds of static stretching and you also do dynamic stretching, you get the best of both worlds" after a good warm-up, says David Behm, an exercise physiologist at Memorial University of Newfoundland in Canada. "You increase range of motion, decrease injury risk and get no change in performance."
Stretching has become a frequent focus of scrutiny among researchers and athletes who want to maximize performance while minimizing injury risk. In particular, questions have long swirled around static stretching, which involves holding positions to the point of slight discomfort.
Debates have endured because studies have offered conflicting results. Some research has shown that static stretching can increase range of motion, in turn lowering the chances of straining muscles. But plenty of other studies have found that static stretching reduces strength, power, balance, reaction time and more. In general, there appears to be about a five percent reduction in performance when static stretching is done before an athletic test.
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Still, it has been hard to draw conclusions from the large mass of stretching research, in part because of a huge range in study protocols that vary in in the kind and length of stretching, the types of measurements taken afterwards, and the timing of assessments.
Recent studies, meanwhile, have suggested that the duration of stretching may matter more than whether people stretch or not, at least when it comes to speed and strength. In a 2012 review of more than 100 studies, two researchers from Australia and the United Kingdom concluded that stretching reduced performance only when stretches went on for longer than a minute.
For the new study, Behm and colleagues wanted to take a closer look both at the amount of time spent stretching, as well as how static stretching might affect athletes in combination with other kinds of warm-up activities.
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After narrowing their analysis down to 125 studies that fit their criteria, the researchers concluded that the benefits of stretching can outweigh the harms if done in a certain way. Specifically, Behm says, a workout should begin with five to 10 minutes of aerobic activity that increases core body temperature by a degree or two – enough to break a sweat.
Subsequent static stretches should last no more than 60 seconds per muscle group, and they should be followed by sport-specific dynamic stretching activities before the real work begins, the team reports in the journal Applied Physiology, Nutrition, and Metabolism.
Although evidence that links stretching to injury risk is still incomplete, Behm argues that static stretching can make injuries less likely by increasing range of motion, particularly for middle-aged athletes. With short-duration stretches, he adds, performance declines are minimal.
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The reason for the benefits of shorter-duration stretches, he suspects, has to do with receptors in muscles that fire when stretching begins, causing muscles to contract. As a stretch goes on and on, though, this rate of firing drops, leading to a depression of the motor system.
Even if a little stretching incurs a small loss in throwing distance or running speed, effects probably won't matter much for the average, amateur athlete, says Michael Bergeron, president of Youth Sports of the Americas in Birmingham, Alabama. In his view, studies that try to assess the influence of stretching on sports fail to take into account all of the other factors that go into athletic performance, including the psychological impact of maintaining a certain routine or feeling a certain way.
"There are a lot of integrated inter-dependencies of biological systems that need to work together" to influence sports performance, he says. "As long as the body is being progressively prepared for activity and not being overloaded, it's all good."
It makes sense that stretching for shorter intervals would reduce injury risks, adds Pablo Costa, an exercise physiologist at California State University, Fullerton. But he disagrees with the conclusion that any amount of static stretching before exertion could be more good than bad.
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Although the mechanism is still up for debate, he says that stretching weakens tissues and reduces strength, perhaps by increasing the time it takes for signals from the brain to reach muscles and make them contract. Even though the delay totals just milliseconds, that can add up to the difference between winning and losing for a serious athlete.
But there's a twist that suggests timing matters, he says. Other studies have shown that chronic stretching programs done independently of exercise sessions can improve strength over the long-term.
"Based on what I have found personally, I don't recommend that people engage in stretching prior to exercise," Costa says. "I would leave the stretching for after exercise during the cool down period – or during a whole separate time of day for athletes who have time available."