Electromyographic study on shoulder movements

Abstract

The teres minor muscle performs an important function during external rotation and extension, and was active as a synergist during flexion, abduction and adduction, and inactive during internal rotation. Deltoideus (pars clavicularis), pectoralis major, latissimus dorsi and coracobrachialis were inactive during internal rotation, and subscapuralis was the only muscle that was active during this movement without exertion. Infraspinatus and teres minor perform important functions during external rotation, but deltoideus (pars spinata) was inactive during this movement. Teres minor did not always function the same as infraspinatus. Teres minor was particularly active during the latter half of abduction and during adduction, but infraspinatus was active during abduction and inactive during adduction. Teres major did not always function the same as latissimus dorsi. Teres major was particularly active during extension and adduction, but latissimus dorsi was active during flexion, extension, abduction and adduction. It is believed that the active condition of the participating muscles differs in relation to the time taken to carry out a shoulder movement.