Effect of temperature on muscular strain in simulated packing work

Abstract Muscular strain in packing work was studied under three conditions: the subjects, wearing the usual three-layer clothing of the food processing industry, performed the work at 19,4 or 4†C whilst wearing an electrically heated vest which provided 100–150W additional heat. Work simulation consisted of four 30 min working periods with 5 min resting periods in between. The task was to pick up a group of four sausages every 4 s, separate the sausages by cutting them with a fixed blade, and place the sausages into a box. Skin and rectal temperatures were measured continuously and stored at 1 min intervals. thermal sensations were recorded at 15 min intervals. Muscular strain of selected muscles in the lower and upper arm and shoulder area was quantified by EMG-measurements. Mean skin temperatures at the end of the experiment were 33.3,29.7 and 32.3°C (average of both men and women, n =16) at 19,4 and 4°C with the vest, respectively. In comparison to working at 4°C, working at 19°C generally lowered the level of muscular strain. The most conspicuous effect was seen in the upper arm in the triceps muscle, where a warm environment decreased muscular strain by 33% in women and 65% in men. The heated vest decreased muscular strain only in women. The effect was seen in finger extensors, biceps, deltoideus and trapezius muscles. The results suggest that muscular strain during packing work can be decreased by warming. However, if torso heating is used, the heating power must be easily and individually adjusted to avoid uncomfortable hot sensations and sweating. Moreover, the bulkiness of the vest should be minimized.