For years, common wisdom has been to stretch out your muscles before a workout. It was thought that stretching loosened up the muscles and prevented injuries. It seems that common wisdom was wrong, and stretching before a workout can increase the chance of injury and decrease your performance…unless it’s done right.

Several recent studies, including a very large study in Hawaii, have shown that stretching before exercise does not decrease the chance of injury, and in some groups—notably, white males—pre-exercise stretching was associated with more injuries. On the other hand, people who stretched after their workouts had fewer injuries.

Even in the light of new research about stretching before a workout, exercise professionals and physicians agree that stretching itself has significant health benefits. Stretching improves flexibility and the range of motion of your joints, helps your balance and posture, improves circulation, relieves stress and feels good. Although stretching does not increase the rate of healing after a sports injury, it may decrease the pain associated with the injury. It also helps prevent joint stiffness that occurs with age. The question is not if you should stretch; it’s when you should stretch.

The most important thing to remember about stretching is that it’s essential to warm up first. Stretching cold muscles is like stretching a frozen rubber band—something is likely to break. Ten to fifteen minutes of light cardio exercise—just enough to make you break a sweat—will warm your muscles and make them more supple and resistant to injury.

After warming up, light stretching of the muscles you will in your workout use probably won’t hurt. If maximum performance is important to you, however, you might want to save the stretching for later. Stretching forces the muscles to relax and weakens them temporarily.

If you want to really stretch, you can do it as a separate workout or after your regular workout, when your muscles are warm. The keys to a good stretching workout are:

• Warm up first.

• Stretch slowly and hold the stretch for about 30 seconds. Stretching slowly keeps the muscles from tearing and allows them to adapt to the lengthening you are imposing. Holding for 30 seconds helps maintain the muscle lengthening, so you can often stretch further with the next one.

• Stop if it hurts. Don’t stretch past pain. Just stop and hold that position for a few seconds. If the pain doesn’t subside, release the stretch. If it does subside, however, you can gently stretch a little further, again stopping if it hurts.

• Stretch opposite sides equally. If one side is painful or injured, there’s a tendency to either not stretch that side or, if it feels good, to only stretch that side. Make sure you stretch the opposite side an equal distance and an equal number of times.

• Breathe. It’s natural to hold your breath, so check yourself to make sure you’re breathing during stretches.

• Don’t bounce while stretching.

Stretching before a workout is no longer universally recommended; stretching after the workout may be more effective.