The Effect of Humeral Head Depressor Muscle Co-Activation Training in Terms of Functional Outcomes

Recent systematic reviews, and meta-analyses concluded that rotator cuff and scapular strengthening exercises should be included in rehabilitation programs for patients with middle-size rotator cuff muscle tear. Superior translation of the humeral head is one of the factors adversely affecting this rehabilitation process. Aside from rotator cuff muscles, opposition of superior humeral head translation can be achieved by the glenohumeral adductors (i.e. pectoralis major, latissimus dorsi muscles, and teres major), which act as humeral head depressors by means of the medio-inferior vector created by the orientation of their tendons. Recruitment of the glenohumeral adductors has been shown to decrease subacromial narrowing in elevated arms in asymptomatic individuals, and is thought to be a coping mechanism to decrease pain in individuals with rotator cuff tear. However, to the best of our knowledge, the efficacy of humeral head depressor muscle co-activation training on functional outcomes in patients undergoing arthroscopic shoulder surgery after middle-size rotator cuff muscle tear has never been evaluated in patients with middle-size rotator cuff muscle tear. Since recruitment of those muscles could prevent a decrease in subacromial space during arm elevation, it could potentially lead to improved exercise performance, earlier benefits and better treatment outcomes compared to routine rotator cuff strengthening exercises. Thus, the aim of this study was to investigate the efficacy of the humeral head depressor muscle co-activation training on functional outcomes in patients undergoing arthroscopic shoulder surgery after middle-size rotator cuff muscle tear.