Combined influence of transfer distance, pace, handled mass and box height on spine loading and posture.

Work-related low back disorders are commonly associated with handling tasks. The objective of this study was to determine the combined influence of distance, pace, handled mass and height, on back loading and posture during free box transfer. Kinematics and kinetics of 17 handlers were recorded during a box transfer task between two pallets. Four-way repeated measures ANOVA were conducted on four lift-deposit height conditions (from lift and deposit of 0.16 or 1.16 m), three distances between pallets (1.5, 1.0 and 0.5 m), two handled masses (10 and 20 kg) and two paces (free and faster). The interaction between distance and height on back loading and posture (P < 0.001) showed that increasing distance to more than 1 m is not recommended to avoid unnecessary cumulative loading. The shorter distance of 0.5 m, which generally reduced the most spine loading, may increase it for transfers varying in height. The effect of pace to reduce spine cumulative loading and increase the peak asymmetric loading (P < 0.05) was accentuated by mass, height and distance. The combined factors revealed the importance of tradeoff between peak, cumulative and asymmetric loading.

Biomechanical analysis of manual material handling movement in healthy weight and obese workers.

The risk of back injury during work remains high today for manual materials handler. The purpose of this study is to identify the potential presence of compensatory strategies in obese and non-obese handlers and evaluate the impact these strategies have on trunk kinematics and kinetics. The biomechanical and ergonomic impacts in 17 obese and 20 healthy-weight handlers were evaluated. The task studied consisted in moving boxes from a conveyor to a hand trolley and back. The results show that the anthropometric characteristics of obese handlers are linked to a significant increase in peak lumbar loading during lifting and lowering of boxes. Few postural differences between the two groups were observed. These results suggest that the excess weight of an obese worker has a significant added effect on the musculoskeletal structures of the back, which exposes obese handlers to a higher risk of developing a musculoskeletal disorder during load handling.