Functional Electrical Stimulation (FES) enables paraplegics to move their paralyzed limbs; the skeletal muscles are artificially activated. The purpose of this study is to establish a mechanical muscle model for an artificially activated muscle, based on a Hill-type muscle model. In comparison to modeling a physiologically activated muscle, for the artificially activated muscle, a number of additional parameters and their influence on the force generation has to be considered. The model was implemented into a forward dynamic simulation of paraplegic cycling. The stimulation patterns were optimized for surface stimulation of gluteus maximus, quadriceps, hamstrings, and peronaeus reflex. A simulation of a startup with 50% of maximum activation in the optimized stimulation intervals analyses drive torques and mean power per cycle and the resulting riding performance of the rider-cycle system. For validation of the simulation, the results were compared to measurements of the forces applied to the crank during steady-state cycling of a paraplegic test person.
Investigation of force generation mechanism in skeletal muscles through Huxley-type muscle models
