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From World War II until the late 1990s, athletes and daily plodders alike were told that the key to flexibility, injury reduction, and better performance was to stretch and hold. (Think of the old hurdler’s sit-and-reach.)

Then in the late 1990s the pendulum swung: researchers found that performance decreased when people exercised right after this type of “static stretching,” when measured by power and force. One of these researchers, David Behm, found that those who held long static stretches before working out suffered from decreased balance and slower reaction times when they exercised immediately after stretching.

Today, most people who stretch before working out now perform “dynamic stretching” instead, which includes movements like crab walks, leg swings, and “Frankenstein” leg raises. But Behm says this may be the wrong approach as well and the best way to stretch before exercise may be more nuanced.��

Behm is a research professor at the School of Human Kinetics and Recreation at Memorial University of Newfoundland in Canada and much of his work is focused on what happens to muscles during exercise. But he first started thinking about stretching more than 15 years ago, when he first read a study that that found impairments in performance after using stretching as a warm-up. Behm wasn’t just academically curious. The doctor��had a brief career as a professional football player. (“One might say that I had a cup of coffee in the Canadian Football League,” he jokes). As a fullback, he often tried to make up for a lack of speed with strength training and lots of stretching, which likely made him the only guy in the CFL who could squat 500 pounds but also do the splits.

In a new study, Behm and colleagues wanted to know if previous research mimicked how people limber up in the real world—and whether the findings and recommendations that stemmed from these studies thus were valid.

To do so, Behm and his co-authors dissected more than 200 stretching studies published in English between 1989 and 2014. They examined not only the type of stretching, but also the duration of the stretch.

The researchers immediately found problems. Participants were almost always tested in exercise after as much as 30 minutes of stretching. “But who does 30 minutes of stretching?” he asked. (Behm says he, too, was guilty of designing similar studies.)

What’s more, participants often were told to hold stretches for long durations—at least one minute per muscle group. People might do that during yoga class, but rarely right before they exercise, he points out.��

When participants showed drops in performance, authors blamed static stretching instead of asking whether extended periods of static stretching might have caused the impairment.��The new study doesn’t spare dynamic stretching, either.��When the researchers looked at 48 studies that together measured 80 kinds of after-stretching performance—from sprint speed to jump height—they found only trivial positive changes.��“Generally, not much happened,” said Behm.

The resulting ��appeared in December online in the journal Applied Physiology, Nutrition, and Metabolism. ��

Here are some more findings, and some new stretching advice from Behm:

Stretching: Do It

In case you’re feeling whipsawed by all the advice, here’s the upshot: keep stretching. The benefits indeed seem to outweigh the costs, in terms of performance, range of motion, and injury reduction, the study found. Of course, to see any benefits, stretch the muscles relevant to your activity.

Do It for Five or More Minutes

To reduce injuries, you’ve probably got to stretch for more than five minutes in total, doing a few different stretches. When you do, the benefits of static stretching for helping your range of motion��and reducing injury to your muscles “at least balance, or may outweigh” any slips in your performance you see, according to the authors.��

Go Long…But Not If You Go Long��

Duration—how long you should hold that static stretch—has created more confusion than perhaps any other factor around stretching. Studies in North America and Australia have found that holding a pose for a minute or longer can lead to between a five- and 7.5 percent impairment in various measures of performance, when exercise is performed immediately after the long stretches, says Behm.

Don’t let that stop you from doing deep stretching. “What you really want to do, if you’re a stiff old man, or -woman, or young person, you should do longer stretching, but you shouldn’t be doing it right before you do your sport,” Behm advises. Yoga is great—just don’t do a class prior a six-mile run. Think of deep stretching as another conditioning exercise more akin to, say, bench press, says Behm—and you wouldn’t do five sets of bench press twice in one day.

Dynamic Stretching—Should You Even Bother?

Just because dynamic stretching didn’t seem to greatly increase performance doesn’t means it’s worthless. “Dynamic stretching does help improve range of motion,” Behm says. It also “elevates core temperature which can increase nerve conduction velocity, muscle compliance, and enzymatic cycling, accelerating energy production,” according to the recent study. Translation: unlike static stretching, which tells the body’s muscles to calm, dynamic stretching excites your body’s systems and gets the body prepared for further movement.

Behm recommends incorporating some controlled movement into your pre-workout routine. Dynamic stretching can be done close to your start of the activity.

Danny McMillian, a clinical associate professor at the University of Puget Sound who has written about stretching, agreed with the paper on this. “Use SS (static stretching) as you see fit, but respect the fact that it might decrease nerve to muscle responsiveness. Therefore, follow SS with movements (and rate/loading of movement) that mimic your sport,” McMillian wrote in an email.��

Get in the Goldilocks Zone

Just as we’re not all the same, and not at the same level, not every person should be doing the same stretching, says Behm.

Consider Olympic sprinter Usain Bolt. He’s a high-performance machine—a Ferrari, says Behm, who talks about Bolt in his smart .��Bolt is only interested in performance. He wants to be taut, tight, all suspension. He has less than 1/10 of a second to land, regroup and explode upward again.

For an elite like Bolt, static stretching right before a race would be a disaster, says Behm. After all, add 5 percent to Bolt’s time in the Olympics and he becomes Gerald Phiri of Zambia, who came in 15th place, or second-to-last, in the semi-finals, says Behm in his talk. “Five percent is the difference between celebrity and anonymity. And it cost this guy millions of dollars.”��

The difference, of course, is that the rest of us aren’t Bolt. And we’re not Ferraris. “If you’re an elite athlete, then you might compromise your health for performance. Elite athletes are not always the epitome of health,” he says.

If you want to be healthy and fit for the long haul, don’t be a Ferarri; be a Cadillac, says Behm. Cadillacs have soft suspension. When you hit a pothole in a Caddie, it absorbs the insult and keeps moving, he says. “You want your muscles and tendons to absorb the forces, so you're joints aren’t taking a lot of beating.”��

To be a Cadillac, “Strive to be in the Goldilocks Zone,” says Behm. “Goldilocks Zone means you want to have muscles that are just tight enough so that you get an efficient transfer of energy when you hit and go, in whatever sport you’re doing. “But you want muscles that are just flexible enough, that it doesn’t impair your stride length.”

How do you achieve that?

As part of your warm-up, Behm suggests doing four static stretches of six seconds each, in the relevant muscle groups you’ll be using. Combine that with some dynamic stretches, “And you should be fine. You should be in that Goldilocks Zone.”

Hold That Stretch Longer Before You Hit the Mountains

Eccentric exercise—squash, downhill running—can tear up muscles. (It’s why your quads are fried after coming down the mountain on that weekend backpacking trip.) In their review, researchers found that static stretching showed a moderate performance benefit at moderate muscle lengths. Translation: take a few more static stretches when prepping to do eccentric activities in which the muscle lengthens as it is stressed—stuff like hiking downhill.��

And what does Behm himself do?

“When I got to play tennis, I stretch��my hamstrings, my quads, my groin, my adductors, and then I’d stretch my shoulder joint and lower back,” he says. “Usually I’d hold them about 20 seconds each—that’s about seven minutes of stretching” when added up, he says. Next, Behm will do some dynamic stretching—swinging his leg from side to side, for instance. Finally, he’ll step onto the court and slowly, easily begin to hit balls to warm up.

As Behm holds that static stretch for 20 seconds, his subsequent performance on the court might decrease modestly. The question recreational athletes need to ask themselves is, “What’s the cost-benefit analysis?” he says. If you’re a fraction slower to the ball, or you hit that ball a tiny bit slower, “Well, who the hell cares?” he says. “Does it really make a difference in my game? Probably not.��

“But it might make make a difference in whether I get injured or not.”