Background: Poor activation of the serratus anterior (SA) muscle may result in abnormal shoulder rhythm, and
secondarily contribute to impingement and rotator cuff tears. Sequential activation of the trunk, pelvis, and lower
extremity (LE) muscles is required to facilitate the transfer of appropriate forces from these body segments to the
upper extremity. Myofascial connections that exist in the body, and LE and trunk muscles (TM) activity may influence
scapular and upper limb activity. The purpose of this study was to investigate the effect of simultaneous recruitment
of the LE muscles and TM on the SA muscle activation when performing a forward punch plus (FPP) and six
variations of the FPP exercise.
Study Design: Experimental, within-subject repeated measures.
Methods: Surface electromyographic (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
forward punch plus (FPP) movement and six variations in twenty one healthy male adults. The percentage of maximum
voluntary isometric contraction (%MVIC) 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 (p < 0.05).
Results: Pairwise comparisons found that the EMG activity of the serratus anterior (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.
Conclusions: Simultaneous recruitment of the lower extremity and trunk muscles increases the activation of the SA
muscle during the FPP exercise.
Clinical Relevance: Rehabilitation clinicians should have understanding of the kinetic chain relationships between
the LE, the trunk, and the upper extremity while prescribing exercises. The results of this study may improve clinicians’
ability to integrate the kinetic chain model in a shoulder rehabilitation program.
Level of Evidence: 2b
Key Words: Electromyography, kinetic chain, myofascial connections, serratus anterior