Manual handling tasks performed with an upper limbs exoskeleton at the workplace

Abstract

Exoskeletons for industrial applications were designed to physically assist the workers in performing tasks. These new technologies appear as an additional way to prevent work-related musculoskeletal disorders. Limited information is known about the potential benefits and risks of such exoskeletons during work tasks. This study aimed to assess the impact of the use of an upper limbs exoskeleton on the muscular activities, arm kinematic and cardiovascular adaptations during manual handling tasks. Participants had to perform, with a bilateral passive exoskeleton (EXOS) versus without equipment (FREE), three handling tasks, consisting of load lifting in the sagittal plane (LIFT), walking with load carrying (WALK) and boxes stacking with a 90° rotation on the longitudinal axis (STACK). Electromyographic activity of the anterior deltoid (AD), triceps brachii (TB), erector spinae (ES) and tibialis anterior (TA) muscles, arm kinematic, and cardiac cost (CC) were recorded. DA activity was lower for EXOS than for FREE during LIFT and STACK, whereas TB activity was higher. In contrast, TB activity was lower for EXOS during WALK. Furthermore, TA activity was greater for EXOS as compared to FREE during LIFT. No statistical difference in ES activity has been reported during the 3 tasks. Regarding arm kinematic, EXOS has induced an increase of the average angle of elbow flexion as compared to FREE for LIFT and WALK, and a diminution for STACK. Moreover, EXOS was accompanied by a diminution of the average angle of shoulder flexion and shoulder internal rotation for LIFT and by modifications of shoulder abduction angles for WALK and STACK. Finally, CC was similar between both conditions for WALK and STACK, but presented a strong trend to an increase for EXOS during LIFT. The use of an upper limbs exoskeleton seems to be beneficial to reduce the workload of shoulder flexor muscles. Nevertheless, the benefits do not appear without broader physiological consequences, as an increase of antagonist muscles activity, cardiovascular strain and changes in arm kinematic. Moreover, the advantages and disadvantages of this exoskeleton do not show themselves in the same manner, according to the movements realized by the workers.