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Motor unit recruitment during neuromuscular electrical stimulation: a critical appraisal

  • C. Scott Bickel
  • Chris M. Gregory
  • Jesse C. Dean
Mini Review

Abstract

Neuromuscular electrical stimulation (NMES) is commonly used in clinical settings to activate skeletal muscle in an effort to mimic voluntary contractions and enhance the rehabilitation of human skeletal muscles. It is also used as a tool in research to assess muscle performance and/or neuromuscular activation levels. However, there are fundamental differences between voluntary- and artificial-activation of motor units that need to be appreciated before NMES protocol design can be most effective. The unique effects of NMES have been attributed to several mechanisms, most notably, a reversal of the voluntary recruitment pattern that is known to occur during voluntary muscle contractions. This review outlines the assertion that electrical stimulation recruits motor units in a nonselective, spatially fixed, and temporally synchronous pattern. Additionally, it synthesizes the evidence that supports the contention that this recruitment pattern contributes to increased muscle fatigue when compared with voluntary actions and provides some commentary on the parameters of electrical stimulation as well as emerging technologies being developed to facilitate NMES implementation. A greater understanding of how electrical stimulation recruits motor units, as well as the benefits and limitations of its use, is highly relevant when using this tool for testing and training in rehabilitation, exercise, and/or research.

Keywords

Electrical stimulation Skeletal muscle Motor unit recruitment 

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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • C. Scott Bickel
    • 1
  • Chris M. Gregory
    • 2
  • Jesse C. Dean
    • 3
  1. 1.Department of Physical TherapyUniversity of Alabama at BirminghamBirminghamUSA
  2. 2.Department of Health Sciences and ResearchMedical University of South CarolinaCharlestonUSA
  3. 3.Department of Health Professions, Division of Physical TherapyMedical University of South CarolinaCharlestonUSA

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