All 15 participants completed the incremental peak testing of AC exercise and FES ambulation. All participants reached volitional exhaustion during AC testing; FES tests were terminated when eight of the participants reached volitional exhaustion and seven of the participants could no longer increase the pace of FES walking. Peak metabolic measures of V02, carbon dioxide production (VC02), minute ventilation (VE), and tidal volume (VT) did not differ significantly between FES ambulation and AC testing, but significant differences were found in peak values of respiratory exchange ratio (R) (p < 0.05) and heart rate at peak exertion (p < 0.01), where heart rate was greater during FES ambulation and R was greater during AC exercise.