Physiological Problems in Repetitive Lifting with Special Reference to Tolerance Limits to the Maximum Lifting Frequency

Abstract

An experiment, including 79 measurements, on repetitive lifting of loads from floor to table has been performed with 4 female and 4 male subjects. For each subject: (1) the maximum load which could be lifted from floor to table height using a correct lifting technique, and (2) the maximum oxygen uptake (V_{o 2max} were determined. From (1) relative loads of approximately 10%, 25%, 50% and 70% were calculated, and lifting with at least three different frequencies were performed with each relative weight. The lifting procedure lasted 20 min during which the oxygen uptake ([Vdot]_{o 2}) and the pulse rate were measured. The maximum lifting frequency which did not demand more than 50% of the subject's [Vdot]_{o 2} was determined for each relative load for each of the subjects. These maximum lifting frequencies for all subjects and all relative loads were then plotted against relative burdens. Two curves, one for females and one for males, fitting the points best were drawn by eye. The maximum lifting frequency of females is approximately 0.7 of that of males at the same relative burden. The difference is probably due to the difference in the capacity of the oxygen transporting system in the two soxes. From the results of the above experiments guidelines for practical use have been worked out.