Electrical Stimulation (ES) is increasingly being considered as a means to improve cardio-pulmonary performance in patients with reduced exercise capacity. This short review considers the ES signal parameters and protocols used in studies that have included a measurement of oxygen uptake during the session. It suggests that the tetanic signal parameters normally used for muscle strengthening are not suitable for producing a sustained increase in oxygen uptake. Instead, very low frequencies are preferred, perhaps because there is less fatigue of the type 1 muscle fibers.