Real-time visual feedback can cue changes in grip force during electric hand tool operation.

Objectives. Grip force applied during repetitive hand tool use varies amongst individuals and some apply more force than necessary. Augmented feedback may help modify grip force to reduce the risk of developing cumulative trauma disorders but has been scarcely investigated during electric hand tool operation. This study evaluated the feasibility of using real-time visual feedback to modify grip force and forearm electromyography (EMG) during electric hand tool operation. A secondary objective was to evaluate the effect of hand and tool orientation on any effects of visual feedback. Methods. Grip force and forearm muscle EMG were recorded as participants fastened bolts at three locations (low, high and overhead) using an electric pistol-grip nut-runner, without and with visual feedback. Results. Feedback decreased grip force (36.1% decrease; p < 0.001) and EMG of three wrist flexor muscles (22.8-33.0%; p < 0.008). Grip force and EMG also differed between fastening locations, but there were no interactions with condition (baseline and feedback; p > 0.266), suggesting that visual feedback can modify grip force across varying hand and tool orientations. Conclusion. Visual feedback can successfully modify grip force during hand tool operation. However, further investigation is needed to understand how to appropriately implement visual feedback during hand tool operation.