Obesity effect on perceived postural stress during static posture maintenance tasks.

Postural stresses related to manual work tasks may be significantly affected by the bodily condition of workers. One such condition is obesity, which is characterised by excess fat mass in the body. This study empirically examined the obesity effect on postural stress during static posture maintenance tasks. In total, 20 obese and 20 non-obese participants performed static box-holding for a set of 84 working postures defined based on the Ovako Working Posture Analysing System. The participants reported postural stresses using the rated perceived exertion scale. Obesity was found to significantly increase postural stress across the 84 working postures and, also, amplify the effects of postural changes on postural stress. The study findings suggest that ergonomic workplace/job design for obese workers would be a challenge requiring a proactive approach and creativity in problem solving. In addition, the use of ergonomic knowledge in design would be more critical when targeting obese than non-obese workers. The study findings are relevant to ergonomic workplace/job design for obese workers.

A quantitative method for representing balance strategies of goal-directed human motions.

A movement index termed balance strategy vector (BSV) was developed as a research tool for studying human balance strategies during goal-directed motions. For a given motion (motion capture data), the BSV index quantitatively represents its balance strategy by computing how available body joint DoFs' angular motions affect the formation of the wholebody center-of-mass trajectory. The index facilitates easy and intuitive understanding of balance strategies of various human motions and can assist scientific investigations on human balance strategies. As an example demonstrating the utility of the index, the index was used to explore balance strategies of free-style, sagittal-plane load lifting motions.