An analysis of handle designs for reducing manual effort: The influence of grip diameter

Abstract

Biomechanical principles indicate that the risk of upper extremity cumulative trauma disorders (CTDs) can be mitigated by designing tools to reduce manual effort. Specifically, research suggests that handle design should be based on anthropometric considerations. A laboratory study was designed to evaluate the effects of handle diameter on manual effort during a simulated industrial task. Three handle diameters were studied: (1) a handle matched to inside grip diameter, (2) a handle 1.0 cm smaller than inside grip diameter, and (3) a handle 1.0 cm larger than inside grip diameter. The task was performed against three levels of resistance. Applied grip force and surface electromyography (EMG) of select forearm muscles were recorded. The results indicate that grip strength was maximized by the smaller handle. Grip strength was also greater with the matched handle than with the larger handle. There were no differences in grip force exerted with different handles during the experiment. However, because the smaller handle provided the greatest capacity for exerting grip force, effort was reduced when the smaller handle was used. Forearm muscle activity was also reduced when the smaller handle was used. The study indicates handles 1.0 cm smaller than the user's inside grip diameter may reduce effort and the potential for injury.