An electromyographic analysis of two techniques for squat lifting and lowering.

The purpose of this study was to examine the effects of two different alignments of the pelvis and three different loads on electromyographic (EMG) activity of the erector spinae and oblique abdominal muscles during squat lifting and lowering. Each of 15 healthy subjects lifted and lowered loads with the pelvis aligned both in an anterior tilt and in a posterior tilt. Based on total duration, both the lift and the lower were divided into two equal phases. The EMG activity of each muscle was quantified for each half of both the lift and the lower and was normalized to the total EMG produced by the muscle during a maximal voluntary isometric contraction. The results indicate (1) that the EMG activity of the erector spinae muscles was greater when subjects maintained an anterior tilt than when they maintained a posterior tilt; (2) that the EMG activity of the oblique abdominal muscles was greater in the first half of the lift than in the second half for both lifting styles, although the opposite was true for both lowering styles; and (3) that the EMG activity increased with increasing loads. The results suggest that the greater trunk muscle activity occurring with the anterior tilt position may ensure optimal muscular support for the spine while handling loads, thereby reducing the risk for low back injury.