Abstract
The determination of the maximum acceptable weight of lifting using the psychophysical method was examined over a four hour period. Six females lifted a standard milk carton case from the floor to a height of 0.79 m. The subjects chose the amounts of liquid acceptable to them by instructing a helper to increase or decrease the weight of the case. The amount of liquid acceptable to subjects at 4 lifts/min after four hours of lifting was not different from the weight estimated by them after 20 minutes. However, at 8 lifts/min the acceptable amount of liquid decreased with time. These results suggest that a 20 minute period may be sufficient to estimate the maximum acceptable weight for the frequency of 4 lifts/min, but not for the frequency of 8 lifts/min.
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