Study Design: Experimental, within-subject repeated measures. Objective: To determine the influence of lower extremity (LE) and trunk muscle (TM) recruitment on the serratus anterior (SA) muscle activity during the forward punch plus (FPP). Background: Poor activation of the SA muscle may result in abnormal shoulder rhythm, and secondarily contribute to imingement and rotator cuff tears. Sequential activation of the trunk, pelvis, and LE muscles is required to facilitate the transfer of appropriate forces from these body segments to the upper extremity. Myofascial connections exist in the body, and LE and TM activity may influence scapular and upper limb activity. Methods: Surface electromyography (EMG) activity of the SA, latissimus dorsi, and external oblique muscles on the dominant side, bilateral gluteus maximus muscles, and contra-lateral femoral adductor muscles were analyzed in FPP and six variations in twenty one healthy male adults. The percentage of maximum voluntary isometric contraction for each muscle was compared across various exercises using a 1-way repeated – measures analysis of variance with Sidak pair wise comparison as post-hoc test. Results: Pairwise comparisons found that the EMG activity of the SA during the FPP with contralateral closed chain leg extension (CCLE), FPP with ipsilateral closed chain leg extension (ICLE), FPP with closed chain serape effect (CS), and FPP with open chain serape effect (OS) showed significantly higher EMG activity than the FPP. The CS and OS exercises produced the greatest amount of EMG activity for the SA, followed by CCLE and ICLE. Conclusions: Simultaneous recruitment of the LE muscles and TM does increase the activation of the SA muscle during the FPP exercise.
