The Effect of Time in the Psychophysical Study of the Maximum Acceptable Amounts of Liquid Lifted by Females

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.