An electromyographic analysis of shoulder function in tennis players

Abstract

Shoulder injuries in tennis players are common because of the repetitive, high-magnitude forces generated around the shoulder during the various tennis strokes. An understanding of the complex sequences of muscle activity in this area may help reduce injury, enhance performance, and assist the rapid rehabilitation of the injured athlete. The supraspinatus, infraspinatus, subscapularis, mid dle deltoid, pectoralis major, latissimus dorsi, biceps brachii, and serratus anterior muscles were studied in six uninjured male Division II collegiate tennis players using dynamic electromyography (EMG) and synchro nized high-speed photography. Each subject performed the tennis serve and the forehand and backhand groundstrokes, and each stroke was divided into stages. The tennis serve contains four stages. Three stages characterize the forehand and backhand ground strokes. Our results indicate that the subscapularis, pectoralis major, and serratus anterior display the greatest activity during the serve and forehand. The middle deltoid, supraspinatus, and infraspinatus are most active in the acceleration and follow-through stages of the backhand. The biceps brachii increases its activity during cocking and follow-through in the serve with a similar pattern noted in the acceleration and follow-through stages of the forehand and back hand. The serratus anterior demonstrates intense activ ity in the serve and forehand, thus providing a stable platform for the humeral head and assisting in gleno humeral-scapulothoracic synchrony. The tennis serve and forehand and backhand ground strokes are accomplished by complex sequences of muscle activity that incorporate contributions from the lower extremities and trunk into smooth, coordinated patterns. Although our study focused on shoulder function in the uninjured tennis player, it may provide a basis for understanding abnormal shoulder biomechanics that contribute to pain and dysfunction. The serratus anterior deserves special emphasis, for our study showed that its activity is essential to each of the three tennis strokes. Because of the similarities between the tennis serve and overhead throw, a conditioning program comparable to one pitchers use many be appropriate for tennis players.