The biomechanics of tennis elbow. An integrated approach.

Tennis elbow afflicts 40% to 50% of the average, recreational tennis players; most of these players more than 30 years of age. Tennis elbow is thought to be the result of microtrauma, the overuse and inflammation at the origin of the ECRB as a result of repeated large impact forces created when the ball hits the racket in the backhand stroke. Several authors have found that EMG activity in the ECRB, the muscle and tendon complex afflicted in tennis elbow, is high during the acceleration and early follow-through phases of the groundstrokes and during the cocking phase of the serve. Unfortunately, none of the authors gave evidence to support the claim that muscle activity in the ECRB at ball contact is high. In the one-handed backhand, the torques at impact (17-24 nm) will be absorbed by the tendons of the elbow. Giangarra and his colleagues observed that the two-handed backhand "allows the forces at ball impact to be transmitted through the elbow rather than absorbed by the tissues at the elbow." Other authors have reported that players using a two-handed backhand will rarely develop lateral epicondylitis, because the helping arm appears to absorb more energy and changes the mechanics of the swing. As seen by Morris and colleagues, Giangarra and associates, and Leach and colleagues, players who utilize the two-handed backhand have a very low incidence of tennis elbow. These three studies conclude that the two-handed backhand stroke is probably the most effective backhand stroke to prevent lateral tennis elbow. Studies show that wrist extensors are highly involved in all strokes (serve, forehand, and both one- and two-handed backhand strokes). This relatively high involvement (40%-70% MVC) throughout play may result in overload of this muscular group. Thus, tennis elbow may be caused simply by continued use of this muscular system in all strokes, and not just because of the high forces absorbed at impact. Another theory concerning impact states that if the extensor group is already at near maximum contraction, vibrations and twisting movements are transferred directly through the muscle (muscle stiffness at this point would be great) to the tendinous insertion, causing repeated microtrauma. If the muscle is the stiffest element in the system, the force will be transferred to the tendon. It is evident that a need exists for specific study of muscular response during impact. More microanalysis of the impact phase needs to be conducted specifically for the one-handed backhand groundstroke.