Background: Shoulder impingement syndrome (SIS) is a prevalent condition among overhead athletes, characterized by pain, limited range of motion, and impaired shoulder girdle function. Objectives: This study investigated the electrical activity of selected shoulder girdle muscles in different angles of arm abduction/adduction in athletes with and without SIS. Methods: Electromyographic (EMG) activity of selected shoulder girdle muscles (middle deltoid, upper/middle/lower trapezius, serratus anterior, and supraspinatus) during various arm abduction/adduction angles in 30 female overhead athletes (15 with dominant SIS, 15 healthy controls) using surface EMG. Results: The finding demonstrated significantly greater middle deltoid and upper trapezius activity during abduction in SIS athletes compared to controls, while these muscles showed reduced activity during adduction. Additionally, the SIS group exhibited markedly decreased activation of middle/lower trapezius, serratus anterior, and supraspinatus across all tested angles. Conclusions: These findings reveal a distinct muscular imbalance in SIS athletes – characterized by over activity of superior stabilizers coupled with underactivity of inferior/middle stabilizers – which may increase joint stress and injury susceptibility. The study provides valuable insights for developing targeted rehabilitation programs to optimize muscle balance, enhance performance, and alleviate symptoms in overhead athletes with SIS.
