Why Stretching May Not Help Before Exercise

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To stretch or not to stretch? The latest understanding of preworkout routines may have you rethinking yours.

Recently, the New York Times summed up the latest evidence suggesting that static stretching — slowly moving muscles until they just start to hurt and holding the stretch briefly — doesn’t prevent injuries, and actually impairs strength and speed in some athletes. According to the Times, two recent studies support limiting stretching before physical activity. The Times reports:

One, a study being published this month in The Journal of Strength and Conditioning Research, concluded that if you stretch before you lift weights, you may find yourself feeling weaker and wobblier than you expect during your workout. Those findings join those of another new study from Croatia, a bogglingly comprehensive reanalysis of data from earlier experiments that was published in The Scandinavian Journal of Medicine and Science in Sports. Together, the studies augment a growing scientific consensus that pre-exercise stretching is generally unnecessary and likely counterproductive.

One of the studies from researchers at the University of Zagreb reviewed 104 studies of people who only practiced static stretching as their warm-up and found that stretching reduced muscle strength by 5.5%. The second study looked at fit men who completed basic squats while lifting barbells either with or without stretching beforehand. Those that stretched lifted 8.3% less weight than those who didn’t.

And these are not the only studies to report the trend. In fact, most physical trainers haven’t recommended long bouts of stretching before workouts for quite some time. Most suggest just a little light and brief stretch beforehand, and spending more time on recovery stretching afterwards. “It has been a long time since anyone has recommended extensive stretching before exercise, because it has been known for a while now that the best time to stretch is after,” says Richard Cotton, the national director of certification at the American College of Sports Medicine (ACSM).

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So why did stretching become such an indelible part of the preworkout routine? It can help with flexibility and improve range of motion, but trainers say many people conflated stretching with warming up muscles. Most people stretch to prime muscles for the workout to come, but there is little evidence that it prevents injuries. “I think stretching is an important part of the physical-fitness regime, but there have been some misconceptions about it. People think that if they stretch before an activity it will prevent injury, but there are no studies to date that show it alone prevents injuries,” says Lynn Millar, a professor of physical therapy at Winston-Salem State University in North Carolina. “If you go back to training guidelines, they say that stretching is part of it, but not all of it. It should not be done alone as a warm-up.”

What makes stretching so potentially harmful to muscles? Cotton believes muscles may actually lose flexibility when they are overworked, somewhat like what happens when you continually stretch a rubber band. “It gets kind of limp. If you overstretch your muscle and then demand a power activity, it makes all the sense in the world that it doesn’t have the power or force that it would if it hadn’t been stretched,” he says.

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Even the ACSM’s Resources for the Personal Trainer manual isn’t much help in resolving the stretching question, since there isn’t much scientific evidence documenting the risks and benefits of flexibility training; most of the advice on the subject, the manual notes, is based on the personal experiences of coaches, physicians and trainers rather than a solid understanding of human anatomy, physiology and biomechanics. “Unfortunately, the existing science of flexibility training often presents fitness professionals with more questions than answers regarding the benefits and risks of stretching,” the manual reads.

Here’s what is known — stretching and flexibility training can give people a wider range of motion in their joints, which can help them to perform their daily activities and improve balance and posture, which are important in preventing falls and other injuries as people age. The risks of stretching include decreased strength, especially in weight-bearing activities.

So when it comes to preparing for a workout, it may make sense to focus on warming up the body rather than simply stretching muscles. That means adding exercises in addition to light stretching, like jumping jacks, which can prepare the body for intensive activity without making the muscles vulnerable to overwork. “If someone is jogging or walking, I recommend a gentle warm-up that takes less than a minute to stretch the quadriceps, hamstrings and calves,” says Cotton. “I feel better when I do that, but I wouldn’t mandate it for every client. There is value in stretching to increase range of motion and enhance activities of daily life.”

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Of course, everyone’s needs and capabilities are different, and the amount and type of stretching should be tailored to the individual. For instance, athletes like swimmers and gymnasts may spend more time doing dynamic stretches, which involve movements that take the body through its entire range of motion. Anyone who is recovering from an injury, in which there may be considerable scar tissue that limits range of motion may also require a bit more stretching to prevent further damage to joints and muscles.

Stretching does have its benefits, say trainers, it’s just a matter of understanding how to incorporate the right amount and type of stretching into the activity you have planned. For most people, that may mean adding more warm-up routines and cutting back from intensive stretching before exercise, but not writing it off completely. “Some people say, ‘Well if it doesn’t prevent injuries [during exercise], why do it?'” says Millar of stretching. “I say, don’t throw the baby out with the bath water. Stretching keeps your normal flexibility, and research shows keeping it part of your routine, either after your workout or later in the day, can prevent injury.”