Simulation of the 1991 Revised NIOSH Manual Lifting Equation

Digital computer simulation of the 1991 Revised NIOSH Lifting Equation was performed using SLAM II in order to examine the behavior of this equation under a variety of realistic industrial lifting tasks. The results showed that over all conditions studied (represented by 100,000 randomly generated lifting task scenarios), the recommended weight limit (RWL) values for the 99.5% of all tasks were equal to or lower than 12.5 kg or 27.5 lbs. With respect to lifting time exposure, the RWL values for the 99.5% of cases were equal to or lower than 13 kg (or 28.6 lbs) for up to one hour of lifting, 12.5 kg (or 26.4 lbs) for less than 2 hours of exposure, and 10.5 kg (or 23.1 lbs) for lifting over an 8-hour shift. From a practical point of view, the results of this study define the threshold RWL values (TRWL), that can be used by practitioners for the purpose of immediate risk assessment of manual lifting tasks performed in industry.