Stretching and flexibility are a cornerstone to building and maintaining athletic success. Without a properly stretched musculoskeletal structure, sports performance will be hampered and the risk of injury to muscles and connective tissues of the athlete is greatly increased.
While the concepts are used interchangeably, stretching and flexibility are the beginning of a sport continuum; a strong and focused stretching program that emphasizes the principle of balance between the various parts of the body will create greater flexibility in the body of the athlete. Flexibility itself over time produces a greater range of motion in the joints of the athlete; these structures permit the body to move and react, while under control, with increased dynamism and explosiveness, all with a reduced risk of injury as the flexible joint is better equipped to bear and distribute the stress of athletic movement than is a more rigid, poorly, or infrequently stretched joint.
There are numerous examples of the relationship between poorly stretched regions of the body and performance. In most sports, the athlete must adopt a version of the "athletic crouch," a position where the athlete's legs are slightly bent to permit the athlete to move quickly in any direction. The body's center of gravity is also lower and positioned above the feet, which are approximately shoulder width apart, to provide greater balance in movement. The head of the athlete is level and the arms are slightly extended for balance and participation in movement. The basketball dribbler and defender, the American football and rugby tackler, batsmen in both cricket and baseball, and all runners and skiers perform the movements necessary to their respective sports in a variation of this fundamental athletic position.
In moving from the fundamental athletic stance, an athlete with poor flexibility and correspondingly limited range of joint motion will experience limitations on performance. The first such limitation is a reduced ability to jump; if the lower leg muscles and joints are not properly stretched, the muscle power created in the calf muscles will not be completely converted to the jumping action. The second restriction on athletic movement will be observed in the stride length of the athlete; runners with inflexibility in their hips and lower back tend to have a shorter, less economical stride than do more flexible athletes. The third impact of reduced range of motion is noticed in the reduced ability of the athlete to move laterally, a fundamental aspect of all ball sports. Lateral movement becomes limited through the lack of flexibility in the groin, upper leg, and the abdominal muscles and tissues.
Impaired or ineffective throwing motions are also a common result of poor flexibility and resulting range of motion. Any limitation or impingement on the range of motion in the shoulder, elbow, or wrist joints will result in a reduced ability to throw an object.
The companion benefit to a stretching program is the reduction of the risk of injury due to muscle and structural imbalance. All joints in the body are powered by pairs of muscle groups, one of which is responsible for the extension of the joint, the opposing pair being responsible for the flexion, or bending, of the joint. The most prominent example of such muscle group pairs is the knee joint, where the quadriceps is the extender and the hamstring is the flexor. Inflexibility between muscle pairs will often create a circumstance where one muscle will overpower the actions of the other, creating an imbalance and injury. Imbalances due to inflexibility can also occur in a structure such as the lower leg; if the calf muscles and the Achilles tendon are not in balance, an overextension injury to one or the other is likely.
To be effective, stretching must form a part of the daily athletic routine. A series of stretches aimed at loosening the entire body is an essential part of every athletic warm up. In sports that emphasize the effectiveness of the leg function, such as distance running, the athlete will often run very easily for a short period, to generate increased heart rate and blood volume into the muscles before beginning the serious stretches. Hard, vigorous stretches should not be attempted at the beginning of the warm up; as with all athletic preparation, the body must move progressively from passive stretching, where the athlete stretches using the effect of his or her own body weight and gravity, to active stretches where the body is manipulated to achieve a particular desired result, the most demanding aspects of any routine.
Stretching is equally important as a cool down mechanism in both the completion of a training session as well as a competition. To return to a normal and rested state, the body requires a bridge from the higher intensity levels created by the demands of the sport. Stretches that stimulate all muscle groups will have such an effect; to stop the sport activity "cold" will promote muscle and joint stiffness.
Stretching and resulting flexibility are inherent in all calisthenics programs, yoga, and pilates. Each of these disciplines is both a self-contained exercise program, as well as a complement to the development of increased flexibility in any other sport.