Effectiveness of a handle flange for reducing manual effort during hand tool use

Abstract

Forceful manual exertion is a risk factor for upper extremity musculoskeletal disorders. Mechanical considerations and previous research suggest this risk can be reduced by redesigning tools to decrease manual effort. This study sought to determine whether adding a flange to handles would reduce grip force requirements by providing an additional source of coupling between the hand and handle. In the first of two experiments, participants grasped and lifted handles with and without a flange at the top lip of the handle. In the second experiment, participants grasped and pulled handles with and without a flange at the bottom edge of the handle. Each task was performed at three levels of weight or resistance. Grip force was measured using a strain gage mounted inside the handles. Electrical activity (EMG) of select forearm muscles was also monitored using surface electrodes. The main finding was that adding a flange to the handle did not significantly reduce the grip force required to perform either task. However, grip force significantly increased with increased weight or pull resistance. The study indicates that reducing tool weight should be a primary objective for reducing the risk of fatigue and injury during hand tool use.