Effect of Adjusting Pulse Durations of Functional Electrical Stimulation Cycling on Energy Expenditure and Fatigue After Spinal Cord Injury

The purpose of the current study was to determine the effects of three different pulse durations (200, 350, and 500 microseconds [P200, P350, and P500, respectively]) on oxygen uptake (VO2), cycling performance, and energy expenditure (EE) percentage of fatigue of the knee extensor muscle group immediately and 48 to 72 h after cycling in persons with spinal cord injury (SCI). A convenience sample of 10 individuals with motor complete SCI participated in a repeated-measures design using a functional electrical stimulation (FES) cycle ergometer over a 3 wk period. There was no difference among the three FES protocols on relative VO2 or cycling EE. Delta EE between exercise and rest was 42% greater in both P500 and P350 compared with P200 (p = 0.07), whereas recovery VO2 was 23% greater in P350 compared with P200 (p = 0.03). There was no difference in the outcomes of the three pulse durations on muscle fatigue. Knee extensor torque significantly decreased immediately after (p < 0.001) and 48 to 72 h after (p < 0.001) FES leg cycling. Lengthening pulse duration did not affect submaximal or relative VO2 or EE, total EE, and time to fatigue. Greater recovery VO2 and delta EE were noted in P350 and P500 compared with P200. An acute bout of FES leg cycling resulted in torque reduction that did not fully recover 48 to 72 h after cycling.