Electromyography of the shoulder: an analysis of passive modes of exercise

Passive shoulder motion is standard early rehabilitation in patients undergoing rotator cuff repair. A number of rehabilitation protocols exist to obtain this goal. This article evaluated different rehabilitation protocols using electromyographic analysis of the rotator cuff muscles to determine if the different protocols promote passive motion. Ten healthy volunteers underwent EMG to investigate the relative activity of the rotator cuff muscles during various exercises used postoperatively following shoulder surgery. The exercises tested were continuous passive motion machine (CPM), pulley, pendulum, self-assisted bar raise using the contralateral arm for power, self-assisted internal and external rotation, therapist-assisted elevation in plane of the scapula, and therapist-assisted internal and external rotation. The relative activity of the supraspinatus, infraspinatus, anterior deltoid, and trapezius muscles were measured and expressed as a percentage of maximal activity. For all muscle groups tested, the pulley exercise showed significantly more activity than the CPM machine. In the supraspinatus muscle, the pulley exercise averaged 17.6% of maximal activity and 8.7% for the self-assisted bar raise using contralateral arm power compared with 5.0% for the CPM machine. In general, therapist-assisted exercises and Codman's pendulum exercises showed activity that was not significantly different from the CPM machine. These results indicate that CPM and therapist-assisted passive range of motion, by being more passive, may increase the safety margin for obtaining early passive range of motion without disrupting the rotator cuff repair.