Numerical Analysis of the Muscle Force during Abduction of the Shoulder Using the Three-Dimensional Skeletal Muscle Model(<Special Issue>Bioengineering of Biological and Medical Materials)

It is difficult to directly measure the muscle force in living subjects. Since many muscles act cooperatively in a human shoulder motion, computer simulation will be useful to analyze the muscle force. This paper describes a method of numerical analysis of muscle force during shoulder abduction. Three-dimensional skeletal muscle model was constructed from normal volunteer's computed tomography. Muscles were modeled by each straight line vector from the insertion to the origin. Because muscle forces could not be calculated from only the equilibrium equations of force or moment, the optimization method using SQP method was applied to this analysis. The objective function was defined as the square sum of the muscle force divided by the physiological cross sectional area. To determine the vector of the muscle which originated from the wide area, the optimization method was also used to select the adequate origin point for each abduction angle. The results of the analysis showed qualitatively good agreement with the results of electromyography.