The effect of muscle electrical stimulation patterns computed using a forward dynamic simulation on endurance and metabolic response in spinal cord injury subjects during recumbent pedaling

The goal of this research was to develop new stimulation patterns for functional electrically stimulated (FES) recumbent pedaling to enable spinal cord injured (SCI) individuals to exercise longer and at a higher workrate than is possible with existing ergometers.;The second objective was to determine muscle excitation timing patterns for three upper leg muscle sets (Stim3) and three upper and two lower leg muscle sets (Stim5) that lead to increased endurance and work output in FES pedaling. Forward dynamic simulations of FES pedaling were developed to determine electrical stimulation timing that minimized the muscle stress-time integral of the stimulated muscles. The results of the simulations indicated that the computed stimulation timing had the potential to prolong pedaling and thereby provide improved cardiorespiratory and muscle training outcomes for SCI individuals.;The third objective was to experimentally verify the theoretical results from the forward dynamic simulations. Mechanical work, rate of oxygen consumption (VO2), and blood lactate data were measured from SCI subjects pedaling a FES ergometer with Stim3 and Stim5. Subjects performed more work with Stim3 than existing stimulation patterns. No significant differences in work or VO2 were observed between Stim3 and Stim5. Stim5 did increase the blood lactate concentrations compared to Stim3. Stim5 did not decrease the work accomplished but did involve more muscles, which is a benefit to SCI individuals. The experimental results supported the outcomes from the forward dynamic simulations of FES pedaling by SCI individuals.;The first objective was to determine the function and mechanical contributions of the individual muscles to recumbent pedaling at different pedaling rates. EMG, kinematic, and kinetic data were collected and analyzed to determine the muscle excitation on and off timing, joint intersegmental moments, pedal forces, and crank torque. These data were used with a forward dynamic model to develop computer simulations of recumbent pedaling and determine the influence of individual muscle forces on the accelerations of the limbs and crank. The functional roles of the individual muscles did not change with pedaling rate, but the mechanical energy generated by the knee extensors and hip flexors decreased as pedaling rate increased.