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Upper limb discomfort profile due to intermittent isometric pronation torque at different postural combinations of the shoulder-arm system

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posted on 2017-04-12, 11:53 authored by Prabir Mukhopadhyay, Leonard O'SullivanLeonard O'Sullivan, Timothy J. Gallwey
Twenty-seven right-handed male university students participated in this study, which comprised a full factorial model consisting of three forearm rotation angles (60% prone and supine and neutral range of motion), three elbow angles ( 45°, 90° and 135°), three upper arm angles ( 45° flexion/extension and neutral), one exertion frequency ( 15 per min) and one level of pronation torque (20% maximum voluntary contraction (MVC) relative to MVC at each articulation). Discomfort rating after the end of each 5 min treatment was recorded on a visual analogue scale. Results of a repeated measures analysis of covariance on discomfort score, with torque endurance time as covariate, indicated that none of the factors was significant including torque endurance time (p = 0.153). An initial data collection phase preceded the main experiment in order to ensure that participants exerted exactly 20% MVC of the particular articulation. In this phase MVC pronation torque was measured at each articulation. The data revealed a significant forearm rotation angle effect (p = 0.001) and participant effect (p = 0.001). Of the two-way interactions, elbow*participant (p = 0.004), forearm*participant (p = 0.001) and upper arm* participant (p = 0.005) were the significant factors. Electromyographic activity of the pronator teres and biceps brachii muscles revealed no significant change in muscle activity in most of the articulations. Industrial jobs involving deviated upper arm postures are typical in industry but have a strong association with injury. Data from this study will enable better understanding of the effects of deviated upper arm postures on musculoskeletal disorders and can also be used to identify and control high-risk tasks in industry.

History

Publication

Ergonomics;52 (5), pp. 584-600

Publisher

Taylor and Francis

Note

peer-reviewed

Rights

This is an Author's Manuscript of an article whose final and definitive form, the Version of Record, has been published in the Ergonomics 2009 copyright Taylor & Francis, available online at: http://dx.doi.org/10.1080/00140130802396438

Language

English

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