Cardiovascular and metabolic responses during functional electric stimulation cycling at different cadences

Objective: To determine the influence of pedaling cadence on cardiorespiratory responses and muscle oxygenation during functional electric stimulation (FES) leg cycling. Design: Repeated measures. Setting: Laboratory. Participants: Nine subjects with T4 through T10 spinal cord injury (SCI) (American Spinal Injury Association grade A). Interventions: FES cycling was performed at pedaling cadences of 15, 30, and 50 revolutions per minute (rpm). Main Outcome Measures: At each cadence, heart rate, oxygen uptake, and cardiac output were recorded during 35 minutes of cycling. Near infrared spectroscopy was used to quantify quadriceps muscle oxygenation. Results: All pedaling cadences induced similar elevations in cardiorespiratory metabolism, compared with resting values. Higher average power output was produced at 30rpm (8.2 +/- 0.7W, P<.05) and 50rpm (7.9 +/- 0.5W, P<.05) compared with 15rpm (6.3 +/- 0.6W). Gross mechanical efficiency was significantly higher (P<.05) at 30 and 50rpm than at 15rpm. Quadriceps muscle oxygenation did not differ with pedaling cadences. Conclusions: Cardiorespiratory responses and muscle metabolism adjustments during FES leg cycling were independent of pedal cadence. FES cycling at a cadence of 50rpm may not confer any advantages over 30 or 15rpm for cardiovascular fitness promotion in persons with SCI.