Feedback-controlled stimulation enhances human paralyzed muscle performance.

Full Abstract

Chronically paralyzed muscle requires extensive training before it can deliver a therapeutic dose of repetitive stress to the musculoskeletal system. Neuromuscular electrical stimulation, under feedback control, may subvert the effects of fatigue, yielding more rapid and extensive adaptations to training. The purposes of this investigation were to 1) compare the effectiveness of torque feedback-controlled (FDBCK) electrical stimulation with classic open-loop constant-frequency (CONST) stimulation, and 2) ascertain which of three stimulation strategies best maintains soleus torque during repetitive stimulation. When torque declined by 10%, the FDBCK protocol modulated the base stimulation frequency in three ways:
by a fixed increase, by a paired pulse (doublet) at the beginning of the stimulation train, and by a fixed decrease. The stimulation strategy that most effectively restored torque continued for successive contractions. This process repeated each time torque declined by 10%. In fresh muscle, FDBCK stimulation offered minimal advantage in maintaining peak torque or mean torque over CONST stimulation. As long-duration fatigue developed in subsequent bouts, FDBCK stimulation became most effective ( approximately 40% higher final normalized torque than CONST). The high-frequency strategy was selected approximately 90% of the time, supporting that excitation-contraction coupling compromise and not neuromuscular transmission failure contributed to fatigue of paralyzed muscle. Ideal stimulation strategies may vary according to the site of fatigue; this stimulation approach offered the advantage of online modulation of stimulation strategies in response to fatigue conditions. Based on stress-adaptation principles, FDBCK-controlled stimulation may enhance training effects in chronically paralyzed muscle.

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Author information

Author/s: Shields, Richard K (RK); Dudley-Javoroski, Shauna (S); Cole, Keith R (KR);

Affiliation: Graduate Program in Physical Therapy and Rehabilitation Science, The University of Iowa, Iowa City, IA 52242-1190, USA. richard-shields(-atsign-)uiowa.edu

Grants: R01-HD 39445 (Agency:NICHD NIH HHS)

Journal and publication information

Publication Type: Clinical Trial; Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't

Journal: Journal of applied physiology (Bethesda, Md. : 1985) (J Appl Physiol), published in United States. (Language: eng)

Reference: 2006-Nov; vol 101 (issue 5) : pp 1312-9

Dates: Created 2006/10/17; Completed 2006/11/28; Revised 2007/12/03;

PMID: 16809630, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adaptation, Physiological - physiology
Adult
Aged
Electric Stimulation
Electric Stimulation Therapy - methods
Feedback - physiology
Humans

Male
Middle Aged
Muscle Fatigue - physiology
Muscle, Skeletal - physiopathology
Paraplegia - physiopathology; therapy
Spinal Cord Injuries - physiopathology; therapy
Torque

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