Electromyographic activities of the subscapularis, supraspinatus and infraspinatus muscles during passive shoulder and active elbow exercises.

Abstract

Postoperative exercises may increase load on repaired tendons. Differences in the activity of the rotator cuff muscles were assessed during several different types of passive shoulder and active elbow exercises. In 15 healthy subjects, passive forward flexion of the shoulder was performed using a table, pulley and rope, and a cane, and external rotation was performed using a cane and a wall. The active elbow flexion-extension exercise was also performed while holding the upper arm with the contralateral hand. Activation amplitudes of the supraspinatus, infraspinatus and subscapularis muscles were evaluated using electromyography with fine wires. During passive forward flexion, the supraspinatus and infraspinatus muscles exhibited lower activity when using a table compared with a cane (both P<0.01) and a pulley and rope (both P<0.05). Flexion of <90° decreased supraspinatus activation compared with 170° (P=0.047). During external rotation of the shoulder while using the cane and wall, there was no difference in the activity of any muscles. Electromyographic activity during the active elbow exercise was lower in the supraspinatus while holding the upper arm (P=0.018). The table sliding exercise may reduce stress on the rotator cuff during passive forward flexion more than the other exercises do. Decreasing the range of motion to less than 90° in forward flexion activated the supraspinatus less. Moreover, movement of the elbow can be performed holding the upper arm to activate the rotator cuff to a lesser extent. Prognostic study, Level II.