The Effects of Eccentric-focused Exercises on Posterior Shoulder Tightness in Amateur Baseball Players with Subacromial Pain Syndrome: A Randomized Controlled Trial.

Abstract

Posterior shoulder tightness (PST) is highly related to glenohumeral internal rotation deficit and scapular dyskinesis, leading to an increased risk of subacromial pain syndrome (SAPS). Eccentric exercises were hypothesized to improve the ability of posterior shoulder muscles to withstand repetitive eccentric loading to resolve PST. To investigate the effects of additional shoulder eccentric-focused exercises on PST in amateur baseball players with SAPS. Thirty-two male amateur baseball athletes were randomly assigned to the eccentric-focused (EF) or general treatment (GT) groups. The GT group received a 4-week intervention program with hot pack application and stretching exercises, while the EF group received three additional eccentric exercises. The outcome measures included shoulder range of motion (ROM), rotator cuff functional strength ratio and endurance, shoulder pain and function, and scapular kinematics and muscle activation. Significantly more improvement in the change scores for horizontal adduction ROM (4.6˚, p=0.025) and shoulder endurance (6.1 seconds, p=0.01) were observed in the EF group compared to the GT group. Internal rotation ROM, shoulder pain, and function were improved in both groups without group differences. Our research found that the eccentric-focused exercise program positively enhanced shoulder horizontal adduction ROM and endurance. This validates that incorporating eccentric strength control at newly gained angles can improve PST more effectively. Moreover, both groups showed significant improvements in shoulder internal rotation ROM, pain, and function after the intervention, indicating that stretching exercises after hot pack application can be a valuable short-term therapeutic strategy.