著者

埜口 博司 落合 直之 坂根 正孝 宮永 豊

出版者

Japan Shoulder Society

雑誌

肩関節 (ISSN:09104461)

巻号頁・発行日

vol.25, no.2, pp.257-262, 2001

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[Purpose]The purpose of this study was to evaluate the activity of shoulder muscles in various shoulder positions in the external rotational motion.<BR>[Materials and methods]We examined the non-dominant side of shoulders of 8 adult males who did not have any shoulder disorder. We pasted surface electrodes for 7 outer muscles and stuck needle electrodes into 3 inner muscles of each subject. Each person performed isometric external rotation motion in various loads (0,3,9,15Nm) in 6 positions (60&deg; internal rotation, neutral,30&deg; external rotation with arm at side, and neutral,45&deg; external rotation,90&deg; external rotation with arm at 90&deg; abduction position) with a Cybex-NORM770. We obtained electromyograms of each muscle. An electromyogram signal during a maximum manual muscle strength test (MMT) was selected as the normalizing value (100%) for each subject.<BR>Each activity (%MMT) was atatistically compared, using Scheffe's test. The statistical significance was set at 0.01.<BR>[Results and conclusion]During isometric external rotation motion, in internal rotation or arm at side position, the activities of the muscles were low and the activities of the inner muscles were higher than those of the outer muscles, so these positions might be appropriate for rotator cuff exercises in the early phase of rehabilitation. While, in the 90&deg; external rotation with arm at 90&deg; abduction positi on, which is similar to the cocking phase of throwing, the activities of all the muscles including the outer muscles were very high. So we must be careful when we do shoulder exercise in such like position not to overload the shoulder muscles.