Subscapularis muscle activity during selected rehabilitation exercises

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.