Abstract
Considering the human upper limb from the viewpoint of mechanics, every degree of freedom of motion is actuated and controlled by more than two muscles. In this paper we describe a method of numerical analysis of muscle force in a human upper limb during pronation-supination of the forearm joint. Because no muscle force can be calculated from only the equilibrium equations of force moment, the optimization method using Lagrange multipliers, which was proposed by Raikova, was applied to this analysis. Muscles were modeled by a straight line from the origin to the insertion. The analytical results were mostly affected by musculoskeletal geometry, in particular, the results for the short muscles of the forearm exhibited such an effect. Therefore, the muscle paths were determined by using a plastic three-dimensional human upper limb prototype. Parameters in the object function of the optimization method were selected to express the muscle properties acting only in the direction of the contraction. Therefore, the synergist and the antagonist could be separated analytically. The results obtained from this analysis were confirmed by experiments using electromyography.
