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Neuromuscular electrical stimulation and the central nervous system Open Access


Other title
central nervous system
neuromuscular electrical stimulation
Type of item
Degree grantor
University of Alberta
Author or creator
Lagerquist, Olle
Supervisor and department
Dr. David Collins (Physical Education and Recreation/ Centre for Neuroscience, University of Alberta)
Examining committee member and department
Dr. Arthur Prochazka (Physiology/Centre for Neuroscience, University of Alberta)
Dr. Edelle Field-Fote (Physical Therapy, University of Miami)
Dr. Kelvin Jones (Physical Education and Recreation/ Centre for Neuroscience, University of Alberta)
Dr. John Misiaszek (Occupational Therapy/Centre for Neuroscience, University of Alberta)
Center for Neuroscience and the Faculty of Physical Education and Recreation

Date accepted
Graduation date
Doctor of Philosophy
Degree level
Neuromuscular electrical stimulation (NMES) is a common therapeutic tool for persons with movement disorders. The manner in which NMES generates muscular contractions has traditionally been attributed to the depolarization of motor axons underneath the stimulating electrodes, a purely peripheral mechanism, which does not involve the central nervous system (CNS). During NMES however, sensory axons are also recruited, initiating an afferent volley which can affect both spinal and cortical centers. This thesis is focused on identifying how this afferent volley influences NMES-evoked contractions and CNS excitability. Four projects are described in which NMES was delivered to generate plantar-flexion contractions. The first goal was to establish the influence of stimulus pulse width on the central recruitment of motoneurons. Contrary to previous findings, changing the pulse width did not significantly alter maximal soleus H-reflex amplitudes; however, wider pulses resulted in a leftward shift of the H-reflex recruitment curve and increased H-reflex amplitudes on the ascending limb of the recruitment curve. The second goal was to examine the effect of stimulus pulse-width on electromyograpic responses and torque during NMES. During 20 Hz NMES, wide pulse widths depressed motor-waves (M-waves) and enhanced H-reflexes, generating larger contractions with a relatively greater central contribution, than when narrow pulses were used. The third project compared the torque produced during NMES-evoked contractions before and during a complete anesthetic block of the tibial and common peroneal nerves. Results from this project showed that contractions arising from a combination of central and peripheral mechanisms fatigue less than contractions that develop from the recruitment of motor axons alone. The final project investigated how spinal and corticospinal excitability associated with the soleus muscles are affected following NMES, voluntary contractions, or a combination of both. It was found that a combination of voluntary contractions and electrical stimulation induced plastic changes in the spinal circuitry of the stimulated muscle without affecting cortical circuitry or inducing any contralateral effects. Collectively, these experiments highlight that wider pulse widths induce a greater reflexive recruitment of motoneurons which contributes to the evoked torque during NMES, and that the evoked afferent volley reduces fatigue and influences spinal circuitry plasticity in the plantar-flexors. Methods to enhance the afferent volley during NMES are only beginning to be tested in clinical populations and future experiments will determine the potential efficacy for persons with movement disorders.
License granted by olle Lagerquist ( on 2009-08-21T18:00:23Z (GMT): Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of the above terms. The author reserves all other publication and other rights in association with the copyright in the thesis, and except as herein provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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