Gender differences in psychophysically determined maximum acceptable weights and forces for industrial workers observed after twenty years.

PURPOSE: In the year 1991, manual materials handling guidelines were published by Liberty Mutual Research Institute for Safety. In these guidelines, maximum acceptable weights (MAWs) and forces (MAFs) for lifting, lowering, pushing, pulling, and carrying were derived from studies conducted in a 20 year span before the above publication date. The question is whether the present generation of workers has retained the same gender differences and absolute values in psychophysically determined MAWs and MAFs as those reflected in the guideline.
METHODS: Twenty-four female industrial workers performed 20 variations of lifting, lowering, pushing, pulling, and carrying. A psychophysical methodology was used whereby the workers chose a workload they could sustain for 8 h without "straining themselves or without becoming unusually tired, weakened, overheated or out of breath."
RESULTS: In females, MAWs of lifting, lowering, and carrying averaged 53% of the present-day male values, similar to the 55% in the guideline. MAFs of pushing and pulling were 83 and 86% of the present-day male values but slightly higher than the 73 and 78% in the guideline, respectively for initial and sustained forces.
CONCLUSIONS: The similarity of gender differences between the guideline and the present findings was coupled with dramatic decreases in MAWs of lifting, lowering, and carrying. Such decreases may reflect a new psychophysical set point; however, considerations about adjusting existing guidelines on lifting, lowering, and carrying may not be appropriate until additional data from other sources inside and outside the US confirm the present findings.