Optimization of muscle physiological parameters for a computer model of the human shoulder girdle.
The shoulder girdle serves as the platform for all human upper extremity movement and plays an integral role in providing the large range of motion of the shoulder joint. However, computer models representing human upper-extremity biomechanics have suffered from a lack of published data relating to the shoulder girdle. The aim of this study was to validate an existing human upper-extremity model in light of newly-published strength data for twelve shoulder shrugging exercises at various shoulder girdle positions. The three-dimensional model accounted for motions of the clavicle, scapula, and humerus, and was actuated by 19 muscle bundles. The model was used to simulate each of the reported shrugging exercises, while the model’s muscle physiological parameters were optimized to minimize error between the simulated and experimental strength measures. The optimized model accurately reproduced the experimental shoulder elevation and depression strengths, but tended to overachieve for retraction and underachieve for protraction exercises.