Strengthening of the rotator cuff muscles in functional positions is important for the prevention and rehabilitation of shoulder injuries in overhead athletes such as tennis, badminton and volleyball players. The purpose of this study was to evaluate the influence of exercise with 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° abduction and 90° elbow flexion was passively supported with the SBT 1000 and had to be actively held 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 of the deltoid. No significant differences could be shown between control and test group or between the dominant and non-dominant arm. These results suggest that with the use of the SBT 1000-bar rotational shoulder exercise can be performed in a functional position with reduced involvement of the deltoid. This aspect is known to be beneficial for the prevention and rehabilitation of shoulder injuries in overhead athletes.
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