Citation

Giat Y, Pike N. J. Saf. Res. 1992; 23(2): 95-105.

Copyright

(Copyright © 1992, U.S. National Safety Council, Publisher Elsevier Publishing)

DOI

unavailable

PMID

unavailable

Abstract

In an attempt to explain why humans typically lift light objects using the stoop lifting method, as opposed to the recommended squat lifting method, a biomechanical and an electromyographic analysis of both the stoop lift and the squat lift was performed in which the following variables were compared; the peak moment about the knee, the peak EMG activity of the knee extensors, the total mechanical work, and the duration of each lift. Eight subjects were filmed, each using both methods to lift small objects of 2.27, 4.54, and 6.81 kilograms. The mean and standard deviation of these variables for each object were calculated for each lifting method. A discriminant analysis with a stepwise selection was then applied to the these variables to determine which of these variables maximally distinguishes the stoop from the squat lifting method. In addition, a 2 x 3-repeated-measure analysis of variance (ANOVA) was applied to the values representing the peak moment about the knee, the peak EMG activity of the quadriceps muscle, the total mechanical work, and the duration of each lift. The discriminant analysis revealed that, among the investigated variables, the moment about the knee was the variable which maximally distinguished the two lifting methods. It was therefore concluded that humans may naturally prefer the stoop lifting method to the squat lifting method because of the greater demand the squat lift imposes on the knee extensors. The results suggest that the relatively greater mechanical work required to perform the recommended squat lift is also an important factor in explaining why humans naturally prefer the stoop lifting method. These conclusions are limited to the lifting of small objects weighing 6.81 kilogram or less.