Utilization of Direct Estimation Method to Determine the Effects of Task Variables on the Capacity to Lift Loads

Abstract

This paper presents results of a pilot study in which the “direct estimation” method was used to determine the lifting capacity of individuals. Using the capacity of subjects to lift a load from floor to overreach height at frequency of 4 lifts per minute as a base, their capacity to lift under condition of varying task variables was determined. In this study 9 lifting heights, 5 frequencies, and 3 box sizes were used. The amount of load which the subjects were willing to lift was determined by the standard psychophysical methodology. Then the subjects lifted the same loads to various heights at different frequencies using different size boxes. A relationship was established between load lifted to the various lifting heights and the perceived difficulty of the lifting task. A similar relationship was determined for various frequencies and box sizes. An analysis of the results of this methodology reveals that the use of “direct estimation method” provides the effects of task variables on the amount of the lifted load accurately in a short period of time.