Stretching is the activity of gradually applying tensile force to lengthen, strengthen, and lubricate muscles, often performed in anticipation of physical exertion and to increase the range of motion within a joint. Stretching is an especially important accompaniment to activities that emphasize controlled muscular strength and flexibility, such as ballet, acrobatics or martial arts.
Stretching is also believed to help to prevent injury to tendons, ligaments and muscles by improving muscular elasticity and reducing the stretch reflex in greater ranges of motion that might cause injury to tissue. For example, some research still in the preliminary stages has found soccer players reduced injury risks by stretching, however the number of players studied was not large enough to draw a firm conclusion. For sports such as tennis, where one of the long-term goals of stretching is to gradually increase static range of motion, the cool-down is an ideal time to systematically program a long-term increase in static flexibility.
In addition, stretching can reduce delayed onset muscle soreness (DOMS). While stretching before or after exercising does not “confer protection” from muscle soreness, current research suggests that stretching can “decrease” or "reduce" pain and soreness after exercise. However, there is no evidence which supports the theory that stretching immediately before exercise can prevent overuse or acute injuries.
There is some controversy over the most effective methods of stretching, and whether some stretches, such as ballistic, or "bouncing", stretches, may actually be harmful.