Biomechanical Models of Hand Coupling for Axial Torque and Push Exertions

Sufficient axial torque and push must be applied with the hands to perform many activities of work, daily living and recreation. Slippage between the hands and work object can result in failure to complete the task and hand injuries. Also, repeated forceful exertions can result in fatigue, damage to the body, and cumulative trauma disorders. This dissertation aims to develop and evaluate biomechanical models that describe axial torque and push on a cylindrical handle in relation to contact force distribution, hand-handle friction, handle size, and the force application direction. In addition, a simple method for measuring hand static friction coefficients proposed in this dissertation can be easily used in the field in a timely manner by ergonomics practitioners or product designers to design more efficient and safer work objects. These findings in this dissertation can be implemented into the design of work objects to reduce required muscle activities for tasks that involve axial torque and push exertion, and thus reduce injuries from hand slippage and the risk of fatigue and musculoskeletal disorders.