Effects on the Trunk of Erecting Pit Props at Different Working Heights

Abstract

The effects on lumbar movement and intra-abdominal pressure of erection of hydraulic props by three methods at different working heights have been studied. Lifting in a squatting position and when on one knee was accompanied by greater trunk stress than when kneeling on both knees. At 3 ft 6 in. (107 cm) working height the magnitudes of lumbar movements and abdominal pressure increases were much less than those at 4 ft 6 in. (137 cm), a difference greater than could be explained by consideration of external work done. The results indicate that the optimum method of prop erection has yet to be evolved, and show that prop erection at 4 ft 6 in. (137 cm) working height by some methods may be unduly hazardous.