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GAZZETTA MEDICA ITALIANA ARCHIVIO PER LE SCIENZE MEDICHE

A Journal on Internal Medicine and Pharmacology


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Gazzetta Medica Italiana Archivio per le Scienze Mediche 2014 September;173(9):431-7

language: English

Differences in EMG activity of selected shoulder muscles during external rotation under various exercise conditions

Yasojima T. 1, Kizuka T. 2, Noguchi H. 3, Shiraki H. 2, Mukai N. 2, Miyanaga Y. 4

1 Department Health Sciences, School of Health and Social Services, Saitama Prefectural University, Koshigaya, Saitama, Japan;
2 Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan;
3 Mito Red Cross Hospital, Mito, Japan;
4 National Institute for Materials Science Tsukuba, Japan


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AIM: The synergistic relationship between the glenohumeral rotator and scapular stabiliser is essential for various shoulder motions. This study was performed to examine electromyographic (EMG) activity of the selected glenohumeral rotator and scapular stabiliser during shoulder external rotation under varying exercise conditions relevant to the position and contraction mode.
METHODS: Seven male subjects with an asymptomatic non-dominant left shoulder participated in this study. Each subject performed shoulder external rotation with various positions (20Abd, 90Abd) and contraction modes (concentric, eccentric) producing a constant target torque of 15 Nm. EMG activity was recorded from the infraspinatus, posterior deltoid as the glenohumeral rotator, and then middle trapezius as the scapular stabiliser.
RESULTS: EMG activity of each selected muscle was significantly lower for eccentric contraction than for concentric contraction in both positions (P<0.05). In the comparison between muscles, the infraspinatus showed significantly higher activity than the posterior deltoid in both contraction modes and positions (P<0.05). The middle trapezius showed significantly higher activity compared with the posterior deltoid in concentric contraction at the 90Abd position (P<0.05).
CONCLUSION: These results suggested that the activity reflecting the synergistic relationship between glenohumeral rotator and scapular stabiliser may differ in response to exercise conditions during external rotation.

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