COMPREHENSIVE MANUAL HANDLING LIMITS FOR LOWERING, PUSHING, PULLING AND CARRYING ACTIVITIES

The objective of this study was to develop a set of mathematical model s for manual lowering, pushing, pulling and carrying activities that w ould result in establishing load capacity limits to protect the lower back against occupational low-back disorders. In order to establish sa fe guidelines, a three-stage process was used. First, psychophysical d ata was used to generate the models' discounting factors and recommend ed load capacities. Second, biomechanical analysis was used to refine the recommended load capacities. Third, physiological criteria were us ed to validate the models' discounting factors. Both task and personal factors were considered in the models' development. When compared to the results from prior psychophysical research for these activities, t he developed load capacity values are lower than previously establishe d limits. The results of this study allowed the authors to validate th e hypothesis proposed and tested by Karwowski (1983) that states that the combination of physiological and biomechanical stresses should lea d to the overall measure of task acceptability or the psychophysical s tress. This study also found that some of the discounting factors for the task frequency parameters recommended in the prior psychophysical research should not be used as several of the high frequency factors v iolated physiological limits.