Most athletes know that stretching the muscles before and after exercising is beneficial to the human body. Many of the perceived benefits of stretching from times past have recently been proven to be myths, however.
One mythical benefit of muscle stretching is the thought that stretching causes muscles to become longer and the joints to move more freely. Range of motion does improve with stretching; however, the muscles do not lengthen. The tension employed while stretching the muscle allows the muscle to relax. The muscle returns to its original size and length after the stretching session is over. Permanent muscle lengthening involves a small amount of muscle damage.
Another myth associated with muscle stretching is the thought that delayed onset muscle soreness (DOMS) is decreased through post exercise stretching. The fact is however, that DOMS is reduced simply by decreasing activities that cause inflammation and damage to the muscles.
Brief, easy stretching before and after a rigorous exercise is beneficial for reducing injury and for loosening up the muscles. Steady, static stretches are much more beneficial and are much safer than bouncy-type stretching.