Can the efficacy of electrically stimulated pedaling using a commercially available ergometer BE improved by minimizing the muscle stress-time integral?

INTRODUCTION The cardiorespiratory and muscular strength benefits of functional electrical stimulation (FES) pedaling for spinal cord injury (SCI) subjects are limited because the endurance of electrically stimulated muscle is low. METHODS We tested new electrical stimulation timing patterns (Stim3, designed using a forward dynamic simulation to minimize the muscle stress-time integral) to determine whether SCI subjects could increase work and metabolic responses when pedaling a commercial FES ergometer. Work, rate of oxygen uptake (VO(2)), and blood lactate data were taken from 11 subjects (injury level T4-T12) on repeated trials. RESULTS Subjects performed 11% more work pedaling with Stim3 than with existing stimulation patterns (StimErg) (P = 0.043). Average (VO(2)) and blood lactate concentrations were not significantly different between Stim3 (442 ml/min, 5.9 mmol/L) and StimErg (417 ml/min, 5.9 mmol/L). CONCLUSION The increased mechanical work performed with Stim3 supports the use of patterns that minimize the muscle stress-time integral to prolong FES pedaling.