[EMG analysis of shoulder muscles during preventive and therapeutic exercise in the overhead athlete]

Strengthening of the rotator cuff muscles in functional positions is one of the important demands in the prevention and rehabilitation of overhead athletes. The purpose of this study was to evaluate the influence of a new shoulder bar (SBT 1000) on the myoelectric activity of the deltoid muscle. Subjects included 12 healthy overhead athletes (control group) and 9 overhead athletes with subacromial pain syndrome (test group). Both groups performed bilateral internal and external shoulder rotations against resistance from a pulley. The position of 90 degrees abduction and elbow flexion was passively supported with the SBT 1000 and had to be actively hold without the SBT 1000. The electromyographic activity of the three heads of the deltoid was determined using surface electrodes. Rectified mean EMG data were analysed by three factor repeated measures ANOVA (group x bodyside x condition). Significant differences (p < 0,05) occurred between the conditions with and without SBT 1000 in all three heads of the deltoid. The percentage of reduction of muscle activity with the SBT 1000 in the dominant arm was 33 %, 29 % and 17 % for the anterior, middle and posterior head. No significant differences could be shown between control and test group or between the dominant and nondominant arm. With the SBT 1000 rotational shoulder exercise can be performed in a functional position with reduced involvement of the deltoid, which could be beneficial in prevention and rehabilitation of overhead athletes.