EVALUATION OF PERFORMANCE CRITERIA FOR SIMULATION OF SUBMAXIMAL STEADY-STATE CYCLING USING A FORWARD DYNAMIC-MODEL

The objectives of this study were twofold. The first was to develop a forward dynamic model of cycling and an optimization framework to simu late pedaling during submaximal steady-state cycling conditions. The s econd was to use the model and framework to identify the kinetic, kine matic, and muscle timing quantities that should be included in a perfo rmance criterion to reproduce natural pedaling mechanics best during t hese pedaling conditions. To make this identification, kinetic and kin ematic data were collected from 6 subjects who pedaled at 90 rpm and 2 25 W. Intersegmental joint moments were computed using an inverse dyna mics technique and the muscle excitation onset and offset were taken f rom electromyographic (EMG) data collected previously (Neptune et nl., 1997). Average cycles and their standard deviations for the various q uantities were used to describe normal pedaling mechanics. The model o f the bicycle-rider system was driven by 15 muscle actuators per leg. The optimization framework determined both the timing and magnitude of the muscle excitations to simulate pedaling at 90 rpm and 225 W. Usin g the model and optimization framework, seven performance criteria wer e evaluated. The criterion that included all of the kinematic and kine tic quantities combined with the EMG timing was the most successful in replicating the experimental data. The close agreement between the si mulation results and the experimentally collected kinetic, kinematic, and EMC data gives confidence in the model to investigate individual m uscle coordination during submaximal steady-state pedaling conditions from a theoretical perspective, which to date has only been performed experimentally.