ELECTROMYOGRAPHIC ANALYSIS OF SHOULDER FUNCTION DURING THE VOLLEYBALLSERVE AND SPIKE

The purpose of this study was to describe the electromyographic (EMG) pattern and relative intensities of 8 shoulder muscles during the voll eyball serve and spike in 15 professional or collegiate-level athletes . The EMG analysis was synchronized with high-speed cinematography to discern phases of the spike and serve. During the spike, the anterior deltoid and supraspinatus functioned together to elevate and place the humerus throughout all phases. During cocking the intraspinatus and t eres minor acted together to rotate the humerus externally. In acceler ation, however, these muscles behaved independently; activity of the t eres minor remained high, whereas the activity of the infraspinatus de clined. The anterior wall muscles functioned io decelerate the humerus during cocking and acted as internal rotators during acceleration. Mu scle activities recorded for the serve Followed similar patterns as th ose seen for the spike, but with lower amplitudes. These data illustra te the complex sequence of shoulder muscle activity necessary to play competitive volleyball.