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Experiments on wrist deviation in manual materials handling.
Drury-CG; Begbie-K; Ulate-C; Deeb-JM
Ergonomics 1985 Mar; 28(3):577-589
The effect of wrist deviation on manual materials handling was evaluated. Nine subjects in a pilot study grasped a handle attached to a box. Handle angles were evaluated in 5 degree increments from 20 degrees ulnar deviation to 20 degrees radial deviation. Anatomical, physiological, and psychophysical measurements were taken. A long duration experiment was then performed in which 15 male and 15 female subjects grasped handles that were attached to 9 or 13 kilogram box weights for 25 seconds. Five handle angles were evaluated. In the pilot study, the subjects found wrist deviations to be somewhat stressful and accommodated for these deviations by changing their hand grip. Handle angles that required radial deviation were more difficult to accommodate than those requiring ulnar deviation. Moderately small deviations from the neutral position were determined. In the next experiment, changing the handle angle from neutral to 20 degrees radial produced the same effect as changing the box weight by an average of 16 percent. As in the pilot study, a handle angle to the ulnar side of neutral was optimum. Subjects allowed considerable slippage to occur at the hand/handle interface while making a minor accommodation in wrist deviation. Wrist deviation was kept to a minimum, generally between 5 degrees radial and 10 degrees ulnar. The authors conclude that subjects avoid deviating their wrists, even at the cost of not having an adequate grasp.
NIOSH-Author; Medical-research; Physiological-measurements; Humans; Ergonomics; Biomechanics; Task-performance; Job-stress; Job-analysis; Work-analysis; Physical-stress; Industrial-processes
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Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division