Recent advances in neuromuscular electrical stimulation (NMES) suggest that sophisticated techniques can exercise and train people aerobically. However, the limits of this exercise modality would be of interest to sportspeople, trainers and rehabilitation experts. Additionally, there are physical and other barriers which prevent many from undertaking aggressive voluntary exercise. Maximum voluntary and peak NMES efforts were assessed for 1) maximal heart rate and oxygen consumption, 2) excess postexercise oxygen consumption (EPOC), 3) lactate and 4) time-to-fatigue while exercising at 65% of predicted maximal heart rate (maximum voluntary versus peak NMES efforts). Heart rates: 195 bpm and 194 bpm; Oxygen consumption: 52 ml/kg/min and 39 ml/kg/min. EPOC: 110.5 kcal and 96.5 kcal; Lactate: 15.0 mmol/l and 15.3 mmol/l; Time-to-fatigue: 4 h and over 6 h. Sophisticated NMES compares well to voluntary exercise with potential applications for sportspeople and some who cannot exercise due to disease or injury.