Subscapularis Muscle Activity during Selected Rehabilitation Exercises

Abstract

Background The upper and lower portions of the subscapularis muscle are independently innervated and activated. Hypothesis Upper and lower portions of the subscapularis muscle demonstrate different activation levels and require different exercises for rehabilitation. Study Design Controlled laboratory study. Methods Fifteen healthy subjects performed seven shoulder-strengthening exercises. Electromyographic data were collected from the latissimus dorsi, teres major, pectoralis major, infraspinatus, supraspinatus, and upper and lower subscapularis muscles. Results Upper subscapularis muscle activity was greater than lower subscapularis muscle activity for all exercises except for internal rotation with 0° of humeral abduction. The push-up plus and diagonal exercises consistently stressed the upper and lower subscapularis muscles to the greatest extent. Conclusions Humeral abduction was found to have a strong influence on the selective activation of the upper versus the lower subscapularis muscle and thus supported the design of different exercise continuums. In addition, the push-up plus and diagonal exercises were found to be superior to traditional internal rotation exercises for activating both functional portions of the subscapularis muscle. Clinical Relevance Our results showing that the upper and lower portions of the subscapularis muscle are functionally independent may affect training or rehabilitation protocols for the rotator cuff muscles.