Abstract
The execution of manual material handling activities in the workplace exposes workers to large lumbar loads that increase the risk of musculoskeletal disorders and low back pain. In particular, the redesign of the workplace is making the execution of pulling activities more common, as an alternative to lifting and carrying tasks. The biomechanical analysis of the task revealed a substantial activation of the spinal muscles. This suggests that the user may benefit from the assistance of a back-support exoskeleton that reduces the spinal muscle activity and their contribution to lumbar compression. This work addresses this challenge by exploiting the versatility of an active back-support exoskeleton. A control strategy was specifically designed for assisting pulling that modulates the assistive torques using the forearm muscle activity. These torques are expected to adapt to the user’s assistance needs and the pulled object mass, as forearm muscle activity is considered an indicator of grip strength. We devised laboratory experiments to assess the feasibility and effectiveness of the proposed strategy. We found that, for the majority of the subjects, back muscle activity reductions were associated with the exoskeleton use. Furthermore, subjective measurements reveal advantages in terms of perceived support, comfort, ease of use, and intuitiveness.
Highlights
Pulling and pushing tasks are becoming more common in industrial settings with the redesign of the workspaces and the introduction of assistance equipment, such as carts or trucks that facilitate manual material handling (MMH) activities [1]
The reason for the lack of statistical significance is probably due to the large inter-subject variability of EMG signals
It emerges from the biomechanical analysis that the execution of pulling activities exposes workers to large lumbar loads that increase the risk of low back pain (LBP) and back-related musculoskeletal disorders (MSDs)
Summary
Pulling and pushing tasks are becoming more common in industrial settings with the redesign of the workspaces and the introduction of assistance equipment, such as carts or trucks that facilitate manual material handling (MMH) activities [1]. A review of epidemiological studies showed that between 9 and 18% of low back injuries were associated with pulling and pushing activities. Occupational back-support exoskeletons are a possible novel solution that can be introduced in the workplace to reduce the incidence of occupational LBP and the risk of developing MSDs, by limiting workers’ lumbar load during the execution of MMH activities [11,12]. They provide to users assistive torques in the sagittal plane, approximately aligned with the lumbar joint. As a matter of fact, for the execution of other activities, which workers may perform in the same workplace, the use of a back-support exoskeleton has not been considered extensively
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