We all know stretching ensures that muscle and tendons are working efficiently; the more conditioned they are, the better they can handle the pounding they'll take from certain types of exercises and sports.

What's less clear is when it's best to stretch -- before or after a workout? The research is so sketchy that even the experts tend to take a personal approach to their stretching routine, based on their particular sport and their body's strengths and weaknesses.

Certain activities tend to tighten muscles more than others, and running -- whether it's the sport itself or the running portion in sports such as soccer or baseball -- is probably the worst culprit, particularly for hamstring muscles.

"That's because running uses the same muscles for the entire activity over and over, and they're not fully lengthened with each stride," says Janna Wentzell, a certified exercise physiologist and kinesiologist and athletic trainer and an anatomy instructor in the School of Recreation Management and Kinesiology at Acadia University in Wolfville, N.S. Wentzell offers the following stretching suggestions.

Warm up properly
Stretching isn't the same as warming up, and you should never stretch when your muscles are cold. Before starting a sport or workout, it's important to warm up for five minutes or longer, depending on your performance goals.

How you warm up depends on the activity you're planning to do. For a sport that includes running, for example, warm up with a light jog; for a racquet sport, do some easy hitting; and before a gym workout, do any cardio activity. "Ideally, we should warm up, then lightly stretch the appropriate muscles for the activity, do the activity, cool down, then stretch more to help with injury prevention," says Wentzell.

Take your time
Move slowly and smoothly and don't hold your breath (breathing deeply and evenly helps increase a stretch). "Know your own limits and let your body be your guide," says Wentzell. "Stretching shouldn't be painful or cause any soreness. If you feel pain, stop."

Use it or lose it
As children, we're very flexible, but we lose that natural flexibility as we age. "Flexibility is something you have to work at on a regular basis," says Wentzell. She admits there are days when she goes for a run and doesn't stretch after her warm-up, maybe because it's a hot day and she doesn't feel stiff. "But I always stretch when I finish," she says. "Given that our flexibility decreases as we age, there is always a place for stretching."

Photography, iStockphoto.com.