Evaluating the Effect of Back Injury on Shoulder Loading and Effort Perception in Hand Transfer Tasks

Occupational populations have become increasingly diverse, requiring novel accommodation technologies for inclusive design. Hence, further attention is required to identify potential differences in work perception between workers with varying physical limitations. The major aim of this study was to identify differences in shoulder loading and perception of effort between a control population (C) and populations affected by chronic back pain (LBP) and spinal cord injury (SCI) in one-handed seated transfer tasks to targets. The effects of the injuries, and associated pain, are likely to produce variations in movement patterns, muscle loading and perceived effort. The main results show that a) the LBP group had the highest movement time required for an exertion; significantly higher than both the SCI and C groups, while the SCI group had significantly longer exertion times than group C, b) the SCI and LBP groups had significantly higher total, maximum, and mean shoulder torques than the C group, c) the mean shoulder effort ratings for LBPs and SCIs were significantly higher than those for Cs, d) LBPs reported higher shoulder effort ratings than SCIs, e) SCIs and/or LBPs were unable to reach some of the targets; and f) the perception of effort tended to increase as a function of the linear distance between the seat and the target shelf. Differences in shoulder loading and perception were attributed to differences in movement velocities and strategies between the groups. These results suggest that workplace adaptation must take into account population specific characteristics.