Benefits of Stretching
Current research suggests that stretching can decrease pain and soreness after exercise. However, no evidence supports the theory that stretching before exercise prevents overuse or acute injuries. Warming up alone has no effect on range of motion, but when warm-up is followed by stretching there is an increase in range of motion. Many people have misinterpreted this finding to mean that stretching before exercise prevents injuries, even though the clinical research suggests otherwise. A better interpretation is that warm-up prevents injury. If injury prevention is your primary objective the evidence suggests you should limit stretching before exercise and increase warm-up.
Most important: don't bounce. Use "static" stretching, slow, gradual and controlled elongation of the muscle through the full range of motion and held for 15-30 seconds in the farthest comfortable position without pain. As you stretch your muscles, you should feel pulling, but no pain. As you hold the stretch, your muscle will relax. As you repeat the stretch, you should have more range of motion. As you feel less tension you can increase the stretch again until they feel the same slight pull. Hold this position until you feel no further increase.