Multi-directional strength and perceived discomfort of shoulder complex

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 discomf ort 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.