The paradox in using electrically stimulated skeletal muscle to pump blood

For over four decades, various methods have been described for the use of electrically stimulated skeletal muscle to pump blood. To date, there has been no way of predicting the efficacy or long-term pumping capabilities of these methods. This article reviews the basic physiological properties of skeletal muscle and relates them to the blood pumping task and illustrates the paradox, namely a high preload is needed for a forceful contraction, but a high prolonged preload produces muscle ischemia and early fatigue. However, the high preload is only required just before muscle contraction. Two methods are described to attain the high preload and high muscle capillary blood flow.