Psychophysically determined asymmetrical lifting capabilities for different frequencies and containers

Ten young male participants were tested their psychophysically determined 4-h maximum acceptable weight of lifting (MAWL) of 90-degree asymmetric lifting for three lifting frequencies (1 lift/min, 2 lifts/min, 4 lifts/min) and three lifting containers (50 x 35 x 15 cm, 70 x 35 x 15 cm, 50 x 50 x 15 cm). The results showed that the MAWL decreased with increasing frequency and container width or length dimension, while the interaction effect of frequency and container on MAWL was not significant. The MAWL ranged from 13.7 kg to 18 kg for the nine (3 frequencies x 3 containers) lifting conditions. When averaged across the levels of the other independent variable, the MAWL decreased by 7.4% and 16.1% for 2 lifts/min and 4 lifts/min as compared with the MAWL of 1 lift/min, respectively, and decreased by 1.6% and 9.4% for 70 x 35 x 15 cm and 50 x 50 x 15 cm as compared with the MAWL of 50 x 35 x 15 cm, respectively. Additionally, the discrepancies between the MAWL data and the recommended weight limits derived from the revised NIOSH equation were discussed.