The Effect of EMG Biofeedback Training on Muscle Activation in an Impingement Population

Background: The shoulder is injury prone and subacromial impingement syndrome (SAIS) is one of the most diagnosed causes of pain in the region. Objective: The purpose of this study was to investigate muscle activity between healthy and SAIS shoulders on the same subject and to understand the effectiveness of EMG biofeedback (EBFB) on bilateral overhead movements. Design: Ten participants (7 male), that tested positive for 2/3 SAIS clinical tests, volunteered for the study. Bilateral muscle activity was measured via electrodes on the Upper Trapezius (UT), Lower Trapezius (LT), Serratus Anterior (SA), and Lumbar Paraspinals (LP). Kinematic testing involved 3 continuous bilateral scapular plane overhead movements before and after EBFB. EBFB consisted of 10 bilateral repetitions of I, W, Y, and T exercises focused on reducing UT and increasing LT and SA activity. Results: Prior to EBFB, no significant difference in muscle activity was present between sides. A significant main effect of time indicated that after EBFB both sides exhibited reduced UT activity at 60 degrees (p = 0.003) and 90 degrees (p = 0.036), LT activity was increased at all measured humeral angles (p < 0.0005), and SA muscle activity was increased at 110 degrees (p = 0.001). Conclusion: EBFB in conjunction with scapular based exercise effectively alters muscle activity of healthy and impaired scapular musculature.