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KMID : 0357220160280020106
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Journal of Korean Society Physical Therapy
2016 Volume.28 No. 2 p.106 ~ p.111
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Effect of Glenohumeral Joint Rotation on Serratus Anterior, Pectoralis Major and Upper Trapezius EMG Activity during Push-up Plus Exercise
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Shim Young-Hun
Nam Ki-Seok
Park Ji-Won
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Abstract
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Purpose: The aim of this study is to determine the effect of glenohumeral (GH) rotation position in modified knee push-up plus exercise (MKPUP) by examining the surface electromyography (EMG) amplitude in serratus anterior (SA), pectoralis major (PM), and upper trapezius (UTz) and the activity ratio of each muscle.
Methods: A total of 22 healthy subjects volunteered for the study. Each subject performed the MKPUP at 0°, 45°, and 90° of GH joint internal rotation. EMG of the SA and PM, UTz was compared between GH rotation positions and each muscle activity ratio. EMG was used to measure the muscle activity in terms of ratios to maximal voluntary isometric contraction (MVIC).
Results: The difference in EMG activity during the exercise in three GH joint internal rotation positions was observed with the SA and the PM. The greater the GH joint internal rotation angle was, the lower the activity of the PM. In contrast, the SA showed higher activity. However, the activity of UT was similar under all conditions. The ratio of the SA and the PM was considerably greater at 90° GH joint internal rotation than at 0° and 45°.
Conclusion: When excessive activation of the PM or imbalanced activation between the PM and the SA occurs, the MKPUP exercise is most effective at 90° of GH joint internal rotation. Use of this position would be a beneficial strategy for selective strengthening of the SA and minimizing PM activation.
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KEYWORD
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Serratus anterior, pectoralis major, upper trapezius, Push-up plus, Glenohumaral rotation position
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