Maximum acceptable weight of lift for an asymmetrical combination manual handling task

This paper presents a study on a combination lift and lower manual handling task and was designed to simulate the loading of grocery bags into car trunks. Eighteen male subjects performed an externally-paced task of lifting grocery bags loaded with steel shots from 15 cm above the floor and over a wooden sill. There were two different sill heights of 70 cm and 90 cm, and for each of these heights there were three different sill depths of 28 cm, 43 cm, and 57 cm. The dependent variables were the maximum acceptable weight of lift. Constant conditions were temperature (23–26°C), humidity (52–62%), horizontal distance of lift (136 cm), and time of day the subjects performed the lifting. A unique lifting sequence and a modified version of the psychophysical methodology were used to determine the maximum acceptable weight that subjects were willing to lift. There were no significant differences in the weights lifted across the two sill heights but weights lifted over the 28 cm sill depth was significantly more than the weights lifted for either the 43 cm depth or the 57 cm depth.