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Date Permissions Signed
Date of Award
Master of Education (MEd)
Health and Human Development
Suprak, David N. (David Nathan)
Cunningham, Wren L.
Chalmers, Gordon R.
The purpose of this study was to determine the effects of body tilt on shoulder muscle activity and repositioning accuracy during humeral elevation to three positions in the sagittal plane (70, 90 and 110 degrees). Thirty eight subjects underwent testing in an unconstrained joint position sense task. Kinematics were measured with a magnetic tracking device while muscle activation was measured with surface electromyography. The joint position sense task consisted of subjects moving their arms to a predetermined positing in space with the help of visual feedback from a head mounted display interfaced with the magnetic tracking device. Subjects were then asked to reproduce the presented shoulder position in the absence of visual feedback. The protocol was performed under two tilts: upright and back 90 degrees from vertical. This allowed for the comparison of joint position sense at the same elevation angles but different levels of shoulder muscle activation by altering the orientation of the subjects in the gravitational field. When comparing these two tilts we found that subjects matched with greater accuracy and precision at 90 and 110 degrees of elevation when they were upright (p < 0.05). We also found that anterior deltoid muscle activity was significantly greater at all three elevation angles in the upright condition. This data, when taken together support the hypothesis that unconstrained shoulder joint position sense is enhanced with increased muscular activation levels.
Western Washington University
Copying of this thesis in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Sahlberg, Jordan D. (Jordan Daniel), "The effects of body orientation and humeral elevation angle on shoulder muscle activity and shoulder joint position sense" (2014). WWU Graduate School Collection. 328.