If a motor nerve is stimulated from an external electrode the resulting action potential will propagate to the innervated muscle and a twitch will be produced. The muscle responds to the artificially initiated nerve signal just as it would a naturally occurring signal. For patients with (for example) spinal cord injury, signals originating in the brain may be unable to reach the desired motoneuron because of a transected cord. In this case the affected muscle is paralyzed, although it may, otherwise, be healthy and capable of excitation and contraction. In this situation an artificial signal initiated in the nerve will evoke a response. Devising strategies for the stimulation of motoneurons to effect desired muscle contraction is the goal of functional neuromuscular stimulation, and the subject of this chapter.
KeywordsFunctional Electrical Stimulation Nerve Trunk Charge Injection Virtual Cathode American Physiological Society
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