Muscles are made of bundles of tiny fibers. In a typical exercise-related muscle strain, these fibers develop microscopic tears. Theoretically, stretching before exercise should make the muscles more pliable and less likely to tear. But when studies have compared rates of injury or muscle soreness in people who stretch before exercise and those who don’t, they have found little benefit to stretching. In fact, stretching a cold, tight muscle could lead to injury.
Instead, try a brief warm-up to get the blood flowing to your major muscle groups and loosen your joints. For example, instead of launching immediately into a brisk walk, spend five to 10 minutes taking a leisurely stroll with long strides, and then increase the pace gradually. Or when you begin exercising on a treadmill or other gym machine, start on a low setting. This will also allow your heart and muscles to respond gradually to the increased demands of exercise.