Corticospinal-evoked responses in lower limb muscles during voluntary contractions at varying strengths

Oya, T., Hoffman, B. W. and Cresswell, A. G. (2008) Corticospinal-evoked responses in lower limb muscles during voluntary contractions at varying strengths. Journal of Applied Physiology, 105 5: 1527-1532. doi:10.1152/japplphysiol.90586.2008


Author Oya, T.
Hoffman, B. W.
Cresswell, A. G.
Title Corticospinal-evoked responses in lower limb muscles during voluntary contractions at varying strengths
Journal name Journal of Applied Physiology   Check publisher's open access policy
ISSN 8750-7587
1522-1601
Publication date 2008-11
Sub-type Article (original research)
DOI 10.1152/japplphysiol.90586.2008
Volume 105
Issue 5
Start page 1527
End page 1532
Total pages 6
Editor Jerry A. Dempsey
Place of publication Bethesda, Maryland, U.S.A.
Publisher American Physiological Society
Language eng
Subject 1106 Human Movement and Sports Science
Formatted abstract
This study investigated corticospinal-evoked responses in lower limb muscles during voluntary contractions at varying strengths. Similar investigations have been made on upper limb muscles, where evoked responses have been shown to increase up to ~50% of maximal force and then decline. We elicited motor-evoked potentials (MEPs) and cervicomedullary motor-evoked potentials (CMEPs) in the soleus (Sol) and medial gastrocnemius (MG) muscles using magnetic stimulation over the motor cortex and cervicomedullary junction during voluntary plantar flexions with the torque ranging from 0 to 100% of a maximal voluntary contraction. Differences between the MEP and CMEP were also investigated to assess whether any changes were occurring at the cortical or spinal levels. In both Sol and MG, MEP and CMEP amplitudes [normalized to maximal M wave (Mmax)] showed an increase, followed by a plateau, over the greater part of the contraction range with responses increasing from ~0.2 to ~6% of Mmax for Sol and from ~0.3 to ~10% of Mmax for MG. Because both MEPs and CMEPs changed in a similar manner, the observed increase and lack of decrease at high force levels are likely related to underlying changes occurring at the spinal level. The evoked responses in the Sol and MG increase over a greater range of contraction strengths than for upper limb muscles, probably due to differences in the pattern of motor unit recruitment and rate coding for these muscles and the strength of the corticospinal input.
Keyword Transcranial magnetic stimulation
Electromyography
Motor system
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Health and Rehabilitation Sciences Publications
School of Human Movement and Nutrition Sciences Publications
 
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Created: Thu, 03 Sep 2009, 09:17:32 EST by Mr Andrew Martlew on behalf of School of Historical and Philosophical Inquiry