Chao, Eric

Force analysis of musculoskeletal joint systems is a redundant problem since the number of unknowns exceeds the number of equilibrium and constraint equations. Such a problem has been analyzed previously by the method of permutation/combination and by optimization technique. This paper combines both methods and discusses the results in the light of a graphical presentation from which unique and nonunique solutions to the problem are elaborated. When the applied load is nominal, multiple solutions are possible to meet the functional requirements. However, under maximum strength, unique solution exists because the redundant muscles reach their physiological limits.

In muscle force analysis, orientations and moment arms of the muscles about a joint provide essential coefficients in the equilibrium equations. For the determination of these parameters, several experimental techniques, including geometric measurement, tendon-joint displacement measurement and direct load measurement, are available. Advantages and disadvantages associated with each of the techniques are reviewed and compared based on our extensive experience.