Subacromial pain syndrome, also referred to as rotator cuff-related shoulder pain (RCS), is characterized by pain localized to the proximal lateral aspect of the upper arm arising from the rotator cuff and other subacromial structures. Although the etiology of RCS is multifactorial, dynamic narrowing of the subacromial space due to impingement of soft tissues within this region has been proposed as a leading cause of chronic rotator cuff pathology. A lack of coordination between the rotator cuff and scapulothoracic muscles may impair shoulder neuromuscular control, leading to varying degrees of microtrauma and degenerative pathophysiological changes in the rotator cuff muscles and surrounding tissues. This dysfunction can result in further narrowing of the subacromial space. Specifically, inadequate superior rotation and posterior tilt of the scapula, combined with the inability of the rotator cuff muscles to resist the superior translation of the humeral head caused by deltoid contraction, may cause impingement of the subacromial soft tissues during overhead dynamic activities. In healthy shoulders, the acromiohumeral distance (AHD) is reported to range between 8 and 15 mm, whereas narrowing of the subacromial space (AHD \< 7 mm) is considered a significant indicator of large rotator cuff tears. Moreover, in patients with rotator cuff tears, proximal migration of the humeral head is associated with tear size and decreased acromiohumeral distance.
In a young and healthy shoulder, the cranially directed forces generated during abduction are balanced by the coordinated contraction of the rotator cuff muscles. This mechanism prevents superior migration of the humerus toward the acromion and subsequent impingement of the subacromial tissues. When the contribution of the rotator cuff muscles to the abduction movement decreases, the deltoid muscle compensates for this deficit. However, this compensatory mechanism results in a force vector that is more cranially oriented rather than mediocranial. The reduction in the stabilizing force of the rotator cuff muscles may impair the ability to counteract the superior forces generated by the deltoid. Both of these changes can lead to superior migration of the humerus and pain in the subacromial tissues.
Insufficient depression of the humeral head during the abduction movement has been associated with pain patterns. During arm abduction, the rotator cuff muscles continue to be the focus of both research and clinical practice. However, several studies have demonstrated that the arm adductors-particularly the latissimus dorsi, teres major, and to a lesser extent the pectoralis major-contribute significantly to humeral head depression during abduction. Activation of these adductor muscles may reduce the mechanical load on subacromial structures during abduction. Elevation movements performed at various angles combined with adductor muscle activity may lead to a physiological increase in the subacromial space. This finding suggests the possibility of conservative treatment in patients with rotator cuff tears (RCT) by strengthening the adductor muscles.
OInvestigation of arm adductor contraction patterns during abduction has shown decreased adductor activation in individuals with rotator cuff tendinopathy. Reduced adductor activation may result in insufficient caudal forces on the humerus, leading to overload of subacromial tissues and persistence of symptoms.Therefore, adductor muscle training programs may be clinically effective in patients with rotator cuff tears. The application of neuromuscular electrical stimulation to increase activation of the teres major and pectoralis major muscles has been associated with a short-term increase in acromiohumeral distance in elderly individuals with rotator cuff tears.
The aim of this study is to increase the activation of the latissimus dorsi muscle, one of the adductor muscles, through targeted exercises, thereby increasing the acromiohumeral distance and facilitating inferior gliding of the humeral head.
