Electromyographic analysis of selected shoulder muscles during a series of exercises commonly used in patients with symptomatic degenerative rotator cuff tears

Abstract

In the nonoperative treatment of degenerative rotator cuff (RC) tears, exercise therapy is advocated. Exercises focusing on strengthening the anterior deltoid (AD) and the scapular muscles are proposed to compensate for RC dysfunction. However, the amount of electromyographic (EMG) activity in these muscles during these exercises remains unclear. Moreover, it is unknown whether muscle activity levels during these exercises alter with increasing age. Therefore, the purpose of this study was to evaluate EMG activity in the deltoid and scapular muscles during 2 series of commonly used shoulder rehabilitation exercisesand assess possible age-related changes in muscle activity. Fifty-five healthy participants (aged 18-60 years) participated in this study. Surface EMG activity was measured in 8 shoulder girdle muscles during a progression of a closed chain elevationprogram (bench and wall slides) and during a progression of previously published AD exercises. In addition, muscle activity was compared between 3 age categories (18-32 years, 33-46 years, and 47-60 years). The proposed progressions exhibited increasing activity from <10% of maximal voluntary isometric contractionto >20% of maximal voluntary isometric contraction for the AD for both exercise programsand for the middle deltoid, upper trapezius, and middle trapezius during the closed chain elevation exercises. Activity levels in the other muscles remained <20% throughout the progression. Age-related analysis revealed increased activity in the AD, infraspinatus, and middle trapeziusand decreased lower trapezius activity during the bench and wall slides. No age-related changes were noted for the AD exercises. These findings may assist the clinician in prescribing appropriate progressive exercise programs for patients with symptomatic RC tears.