Simulation of Simultaneous Muscle Strength and Balance Constraints during One and Two Handed Lifting

Abstract

This paper addresses the complex issues affecting the postures people choose to use when attempting moderate load lifting exertions. In essence, lifting exertions are known to require a person to utilize muscle strength capabilities at each joint while also maintaining balance. As loads in the hand are located further away from the person both muscle and balance requirements increase. By setting population limits to accommodate both a 90%tile muscle strength capability and a functional balance capability within the University of Michigan's 3D Static Strength Prediction Program, it was possible to run a set of trials which demonstrate the importance of both constraints when lifting loads in one and both hands placed at different horizontal distances away from the body. A small study showing the effects of one handed bracing was also performed. Results indicate that subtle changes in body postures and or hand bracing can affect the maximum distance a moderate load can be lifted. This demonstrates the general nature of the biomechanical strength and balance problems associated with the horizontal location of a moderate load, even when one handed bracing is possible.