Comparison of scapular upward rotator muscle activities and activity ratios during three scapular upward rotator strengthening exercises

BACKGROUND: The focus of exercises for restoring the imbalance between scapular upward rotator muscles - upper trapezius (UT), serratus anterior (SA), and lower trapezius (LT) - commonly aims to increase SA and LT activities while not increasing UT activity. OBJECTIVES: The purpose of this study was to compare the activity of the UT, SA, and LT muscles during scapation and protraction exercises, which are two traditional exercises, and during a newly designed scapular upward rotation (SUR) exercise. METHODS: A total of 29 healthy young adult men performed all three exercises with maximum isometric contraction. The electromyographic activities of the UT, SA, and LT were recorded. RESULTS: UT demonstrated the highest activity during scapation. SA activity was the lowest during protraction. However, no difference was found in SA activity during the performance of scapation and SUR. The SA/UT ratio was the highest during scapation. CONCLUSIONS: SUR is a new exercise that can be performed at moderate intensity for shoulder rehabilitation to restore scapular upward rotator muscle imbalance.