Many sport movements involve accelerating an implement, such as a ball, bat or racquet, or transferring force from the ground to the hands. The human body serves as a kinetic chain during these actions, linking and summating forces together in a synchronized effort. Segments of the body are coordinated to elicit a favorable outcome and the segments can be thought of as links to the chain. The overhand serve is an explosive, violent and forceful movement initiated by the strong muscles of the hips, thighs and legs. On the other end of the kinetic chain, the rotator cuff is the muscle group that decelerates the arm and racquet during the overhand serve. The rotator cuff, consisting of four small muscles on the posterior side of the shoulder, serves to stabilize the shoulder joint. If these muscles become tired, overtrained, weak or fatigued, the shoulder is jeopardized and can become injured. A comprehensive shoulder strengthening and flexibility routine can reduce the chance of injury and maximize the effectiveness of the player.
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