Electrical stimulation for enhancing strength and related characteristics of human denervated skeletal muscle

Abstract

Background: Electrical stimulation for enhancing performance characteristics of denervated human muscle has received little attention in the peer-reviewed literature.Objective: The purpose of this brief, descriptive review is to provide a critical appraisal and synthesis of the literature on the use of electrical stimulation for strengthening denervated human muscle, contrasting it with the use of electrical stimulation for neurological weakness or paralysis (due to spinal cord injury) when the peripheral nerve pathways are intact. A review of relevant electro- and neurophysiology will be discussed.Major findings: Beneficial effects of electrical stimulation of denervated muscle have been found for morphologic and ultrastructural characteristics including size, composition, and organization to almost normal muscle characteristics. Force output has also been reported to increase, but to levels far less than those of normal muscles. There has also been evidence of reinnervation of denervated muscle associated with electrical stimulation. Improvements in denervated muscle due to electrical stimulation are similar to those in innervated muscles weakened due to paralysis. Major differences between the two uses of electrical stimulation relate to the stimulation characteristics that must be used.Conclusions: There appears to be promising evidence of beneficial effects of electrical stimulation on denervated muscle. However, there are limitations in methodology and reporting, as well as the level of evidence of the studies in the literature. In addition, the electrical stimulation characteristics used by devices in studies reporting successful outcomes are not currently present in commercially available devices.