A biomechanical analysis of the revised NIOSH equation



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Texas Tech University


The focus of this current study was to determine whether two recommended weight lifting (RWL) conditions would result in the predicted 34kN compressive force at the L5/ Si disc for a variety of lifters. Since the revised NIOSH lifting equation was based on the assumptions of the various approaches—biomechanical, physiological, and psychophysical—in addition to the research findings of numerous experts in the field and feedback from the previous NIOSH equation, it was hypothesized that the mean of all of the peak compressive forces found at the L5 /Si disc resulting from the lifting of the recommended weight limits for two series of lifts would be equal to 3-4kN. The alternate hypothesis was that the mean of all of the peak compressive forces found at the L5 /Si disc would not be equal to 3-4kN. Secondly, there was an additional null hypothesis that the mean of all of the peak compressive forces at the L5 /Si disc for anytime in the lift, for either gender, or for either of the two lifting conditions-all examined both statically as well as dynamically in separate analyses—would equal 3-4kN. Its alternative hypothesis would be that the mean of these peak compressive forces forces at the L5 /Si disc would not be equal to 3 4kN. Hence there was an underlying goal to not only look at the overall quantitative results, but to validate the effects for a variety of conditions as well as subjects. It was then possible to draw conclusions about the extent to which the equation was more protective of males than females, of persons doing certain lifts more than others, or at earlier than later times in a repetitive sequence. The ad hoc committee itself- -M. M. Ayoub, Donald B. Chaffin, Colin G. Drury, Arun Garg, and Suzanne Rodgers acknowledged the need for ongoing validation of the new lifting index's ability to reduce worker injury by accurately predicting hazardous manual materials tasks (Waters et al, 1993). It is hoped that the current study can add to the "margin of safety" for the human back.



National Institute for Occupational Safety and Health, Gravity -- Physiological effect, Backache -- Pathophysiology, Lifting and carrying -- Safety regulations, Backache -- Etiology, Backache -- Prevention