OCCUPATIONAL APPLICATIONSWhen compared to not using a soft-hand exoskeleton, the IronHand® caused both increases and decreases in forearm muscle activity while completing automotive assembly tasks. Surprisingly, although there were reductions in muscle activity when wearing the IronHand®, only a few of these decreases resulted in muscle activity changing such that they fell to below recommended ergonomic thresholds. Despite this, some individuals in our study clearly benefited from the device, and this suggests that there is potential for widespread use of such a device if fine tuned to the individual and task demands. Much work is still required for a design that will allow for optimal physical benefit.
Keywords: Exoskeletons; hand; manufacturing ergonomics.
Background Arm support exoskeletons have received considerable attention as a tool to reduce shoulder and upper extremity demands during automotive tasks. However, less attention has been given to devices that may reduce distal upper extremity demands.Purpose The purpose of this study was to examine if the IronHand® soft exoskeleton could reduce forearm muscle activity while completing automotive assembly tasks.Methods Four female and four male assembly line workers performed various tasks over an 8-h shift, while either wearing or not wearing the IronHand® on separate days. Muscle activity was recorded using surface electromyography (sEMG) from the flexor carpi radialis, flexor carpi ulnaris, extensor digitorum communis, and extensor carpi ulnaris. sEMG was normalized to maximal efforts (%MVE), and Amplitude Probability Distribution Functions (APDF) were used to assess the task demands.Results There were a range of reductions in muscle activity across muscles, including: sEMGRMS (0.09 to 5.7% MVE), APDF Static (0.02 to 2.3% MVE), APDF Median (0.08 to 7.9% MVE) and APDF Peak (0.35 to 17.5% MVE) while wearing the IronHand®. Further evaluation demonstrated that 59% of the recorded task cycles reduced activity of at least one muscle, and 41% of the cycles resulted in an increase in activity.Conclusions Compared to no exoskeleton, the IronHand® produced both increases and decreases in forearm muscle activity, depending on the individual and the specific automotive assembly tasks. Specific use cases need to be carefully determined to ensure the exoskeleton provides the user a physical benefit.