Effect of Load of Shoulder Bag on Human Body

Abstract

The aim of the study was to investigate the effects of different shoulder bag conditions on swing motion of the bag, wobbling motion of human body, load of the shoulder carrying bag and muscle activity of the upper trapezius, lower trapezius and erector spinae during walking. Ten male graduate and undergraduate students walked on a treadmill for about 30 seconds at 4.2 km/h during six conditions; no bag, small size shoulder bag with contralateral shoulder strap, normal size shoulder bag with contralateral shoulder strap, tote bag with ipsilateral shoulder strap, carrying 1 strap shoulder bag ipsilaterally and contralaterally, each containing 10% body weight. The coefficient of variance of vertical motion of the bag and human body, average value of the load on the shoulder, maximum value of moment about the center of gravity of the upper body and %MVC of electromyography for each muscle were compared among bag conditions. Results showed that the effects of different shoulder bag conditions made swing motion of the bag reduced when the size is bigger and the bag is carried contralaterally. And there were no significant differences in wobbling motion of human body. Compared two bags, carrying contralaterally made the change of the distance. Compared three types, the sizes were smaller and smaller, the load was bigger and bigger. But the result couldn't show the types and how to carry effect the load. Compared all moments, the moment was the minimum on the sagittal plane despite the types. Compared all %EMG, the most active muscle is the upper trapezius despite the types.