RELATIONSHIP BETWEEN KNEE-JOINT TORQUE, VELOCITY, AND MUSCLE ACTIVATION - CONSIDERATIONS FOR MUSCULOSKELETAL MODELING

The purpose of this study was to determine if the Hill model, used to describe the force-velocity relationship for isolated tetanically stim ulated muscle, could be modified and used to describe the torque-veloc ity behavior of the knee for maximally and submaximally stimulated qua driceps and hamstrings muscles. Fourteen subjects performed both knee flexion and extension movements at 100%, 70%, and 40% of maximum isome tric effort. For each effort level, the knee was allowed to move again st resistances equal to 75%, 50%, 25%, and 0% of the specified effort level. An electrogoniometer quantified knee angle. Knee velocity was d etermined by numerically differentiating the joint angle data. Torque- velocity-activation (or effort level) data were determined for each tr ial. Model parameters were determined to give the best fit to the data for each subject. Average parameter values were determined for each g ender and for the entire group. The modified Hill-type model accuratel y described the relationship between torque, velocity, and muscle acti vation level for subject-specific parameters but not for parameters av eraged across genders or the entire group.