Katakansetsu
Online ISSN : 1881-6363
Print ISSN : 0910-4461
ISSN-L : 0910-4461
Function
Electromyographic Analysis of the Supraspinatus and Infraspinatus Muscles in the Motion of Shrug in the Shoulder
Hisakazu TACHIIRIToru MORIHARAHaruhiko NAKAGAWAYoshikazu KIDATsuyoshi SUKENARIMotoyuki HORIIToshikazu KUBOYuichiro MIURAHideaki FUKUSHIMAMasao KUROKAWA
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2011 Volume 35 Issue 3 Pages 719-722

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Abstract

Shrug exercise, which is one of the treatments for stiff shoulder and rotator cuff tear, is commonly performed. This exercise is also performed to relax the shoulder after surgery for rotator cuff repair. The effectiveness of shrug exercise for the rotator cuff has not been analyzed. The purpose of this study was to analyze the shrug exercise and to evaluate the usefulness of the shrug. Five asymptomatic male volunteers who had no history of shoulder abnormalities were examined. SSP (supraspinatus) muscle was measured by fine-wire electrodes and ISP (infraspinatus) muscle was measured by surface electrodes. At the time of non-shrug (group N) and shrug (group S), %MVC (maximal voluntary contraction) was calculated in the position of 0, 30, 60, 90 degrees flexion. %MVC of SSP in the position of 0,30,60,90 degrees flexion were 2,8,13,15% in group N, and 32,35,23,32% in group S. %MVC of SSP were increased at each angle. %MVC of ISP were 6,16,25,38% in group N, and 10,17,25,42% in group S. It has been reported that %MVC over 20% is high activity. %MVC of SSP showed over 20% at shrug position in this study, which was considered that shrug motion caused eccentric contraction of SSP muscle with the scapula elevating. From this study, it is considered that shrug excise is useful for cuff training, but may be overloaded on SSP in the early stage after surgery.

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© 2011 Japan Shoulder Society
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