Relative mechanical load on ankle and knee muscles during standing manual materials handling-a study of packing work

The muscular load on the ankle and knee was investigated in 72 different packing work postures. The principle used was as follows; if the load moment about a joint is divided by the counteracting maximum muscular moment, a muscular strength utilization ratio (MUR) is obtained. The MUR was calculated for a large, an average-sized and a small man depending on whether they were all either strong, of mean strength, or weak, thus giving nine MUR values for each posture. Different combinations of box size, box angle, edge height and weight of object handled were studied. The lowest MUR for both the ankle and the knee were obtained in postures with the smallest box angled at 90° to the horizontal, with the upper edge at elbow height or higher. The highest MUR values were with a few exceptions obtained with the largest box angled at 0° or 30° with the upper edge at elbow height or lower.