Manual handling of supplies in free and restricted headroom

The handling of mining supplies still involves manual lifting and carrying, some of which is, of necessity, carried out in restricted headroom conditions. Laboratory studies previously reported in the literature have shown that a reduction in ceiling height led to a progressive increase in truncal stress as measured by intra-abdominal pressure (IAP). However, such studies involved standard stylised lifting procedures. Whether such effects of restricted headroom occurred when free-style lifting, or if the operator compensated by change in lifting style for the restriction, was not known. The effect of reduced headroom was examined on two handling tasks carried out in a simulated underground roadway using eight mining instructors as subjects. Both handling tasks involved the loading, unloading and carrying of stonedust bags (25-30 kg) into different vehicle types. The expected increase in IAP did not occur in the reduced headroom condition for one handling task and only a slight increase (average 3 mm Hg), corresponding to a 7% reduction in lifting capacity, was found for the second handling task. It appears that the subjects, who were free to adopt any posture and handling method, were able to compensate in some way for the effects of the restricted headroom. The vehicle type had a highly significant effect, both in free and restricted headroom conditions, which highlights the importance of design for manual handling tasks.