The influence of parameter values (i.e., fiber optimum lengths and moment arms) and simplification of the geometry of a Hill-type muscle model on the prediction of normalized maximal isometric knee extension moment to knee joint angle relationship was studied. For that purpose, the geometry of m. quadriceps femoris was modeled in considerable detail, and all parameter values were determined on one set of cadaver specimens that had been selected for muscular appearance. The predicted relationship was compared to that measured in human subjects over the full range of physiological knee angles, and a good correspondence was found (r = .96). The good correspondence could be attributed to the substitution of realistic parameter values into the model. Incorporating complex muscle geometry into the model resulted in a small additional improvement of the prediction. It was speculated that the variation in results of cadaver measurements among studies reflects true differences caused by individuals' levels of physical activity in the period preceding death.
K. Meijer and P.A. Huijing are with the Institute for Biomedical Engineering, University of Twente, Enschede, The Netherlands. P. Bosch, M.F. Bobbert, A.J. van Soest, and P.A. Huijing are with the Department of Functional Anatomy, Faculteit Bewegingswetenschappen, Vrije Universiteit, Amsterdam. Direct correspondence to Maarten F. Bobbert, Vrije Universiteit, Vakgroep Functionele Anatomie, Faculteit der Bewegingswetenschappen, v.d. Boechorststraat 9, 1081 BT Amsterdam, The Netherlands.