Electrical Activation of Skeletal Muscle by Sequential Stimulation

Abstract

The ability to voluntarily contract skeletal muscle is lost when the neural connection between the brain and muscle is impaired. Functional Motoric Electrical Stimulation of the Extremities has been proposed as a method of inducing controlled movements in paralyzed limbs by the application of electrical current to the muscle (1). However, a major obstacle in applying such a method clinically is that the muscle rapidly loses its contractile strength. Although the causes and mechanisms of fatigue are not well understood, the repetitive firing of muscle fibers at their fusion frequency and the occlusion of blood flow are likely responsible (2). Sequential stimulation, a technique of electrical activation of skeletal muscle in which the stimulus is multiplexed through a number of electrodes within the body of the muscle, is designed to minimize these effects. We have performed experiments in animals to determine the feasibility of sequential stimulation and preliminary experiments in humans to evaluate an electrode system for chronic stimulation.