Affiliations: Industrial and Management Systems Engineering, West Virginia University, Morgantown, WV, USA
Correspondence:
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Corresponding author: Ashish D. Nimbarte, Industrial and Management Systems Engineering, PO Box 6070, West Virginia University, Morgantown, WV 26506-6107, USA. Tel.: +1 304 293 9473; E-mail:[email protected]
Abstract: BACKGROUND: The shoulder complex possesses sufficient strength to
exert forces in multiple directions. Little is known about the maximum
strength and perceived discomfort while performing multidirectional force
exertions using shoulder complex. In this study, maximum strengths and
perceived discomfort was studied for the exertions performed in the six
anatomical directions. METHODS: Eight healthy, right-hand dominant, male participants were
recruited for the research. A custom-build device was used to measure
shoulder strength at Maximum Voluntary Contraction (MVC). The MVC strength
was measured in the six anatomical directions: 1) anterior (+X), 2) superior
(+Y), 3) lateral (+Z), 4) posterior (-X), 5) inferior (-Y), and 6) medial
(-Z). In addition, isometric exertions were performed in the six anatomical
directions at 20 N, 40 N, and 60 N force levels and the ratings of perceived
discomfort were used to quantify the workload placed on the shoulder. RESULTS: The highest MVC strength was observed in the -Y, +X
directions, followed by -X, -Z directions. The lowest MVC strength was
observed in the +Y, +Z directions. High discomfort was perceived while
performing isometric exertions in +Z and -Z directions. Low discomfort was
perceived while performing isometric exertions in +X and -X directions. CONCLUSION: The results of this study conclude that the MVC
strength and perceived discomfort for the shoulder complex is direction
dependent. The exertions performed in the mediolateral direction impose
higher workload on the shoulder complex compared to the other directions.
