Metabolic cost and subjective assessment of palletizing and subsequent recovery

Twenty-one male blue collar workers repeatedly lifted (palletized) a box weighing 22 kg six times min(-1) for 5 min to a shelf of fixed height. The experimental conditions included two planes of lifting (symmetries), two shelf clearances, and three headrooms. The metabolic (heart rate, caloric cost and ventilation volume) and psychophysical variables (rate of perceived exertion, RPE; visual analogue score, VAS; and body part discomfort ratings, BPDR) were measured during resting, palletization, and recovery phases. In palletization the heart rate and metabolic cost ranged between 25 to 35% of the maximal aerobic capacity. Of the three factors only headroom had a significant effect on metabolic cost (p<0.02) and the BPDR for low back (p<0.05). In the recovery phase only headroom had significantly effect (p<0.001) on metabolic cost. The metabolic recovery took 10 min; however, recovery measured through psychophysical indices appeared to continue for 20 min.