Application issues and theoretical concerns regarding the 1991 NIOSH equation asymmetry multiplier

Abstract The lifting equation developed by the National Institute for Occupational Safety and Health in 1981 was revised in 1991. One goal of the revision was to accommodate non-sagittal lifting tasks, since sagittal lifting tasks are an exception rather than the rule in many industrial settings. This goal of expanding the equation to non-sagittal tasks was accomplished by adding an asymmetry multiplier to the lifting equation. This paper examines the rationale behind the development of the asymmetry multiplier and provides an alternative perspective by reviewing additional literature. The usability of the asymmetry multiplier in industry is discussed with particular emphasis on the applications manual for the 1991 NIOSH equation. The concept of operational definitions required to be able to use the equation as intended is presented. Data from three different sources illustrate the problems and variability associated with measuring asymmetry, as required by the NIOSH equation, in industrial settings. Finally, recommendations for further research and potential modifications to the asymmetry multiplier are presented. Relevance to industry The discussion of measuring asymmetry in industry has particular relevance to industrial settings where the NIOSH equation is applied and asymmetry must be measured.

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