Increases in corticospinal responsiveness during a sustained submaximal plantar flexion

Hoffman, B. W., Oya, T., Carroll, T. J. and Cresswell, A. G. (2009) Increases in corticospinal responsiveness during a sustained submaximal plantar flexion. Journal of Applied Physiology, 107 1: 112-120. doi:10.1152/japplphysiol.91541.2008

Author Hoffman, B. W.
Oya, T.
Carroll, T. J.
Cresswell, A. G.
Title Increases in corticospinal responsiveness during a sustained submaximal plantar flexion
Journal name Journal of Applied Physiology   Check publisher's open access policy
ISSN 8750-7587
Publication date 2009-07-01
Year available 2009
Sub-type Article (original research)
DOI 10.1152/japplphysiol.91541.2008
Open Access Status
Volume 107
Issue 1
Start page 112
End page 120
Total pages 9
Editor J.A. Dempsey
Place of publication Bethesda, MD, USA
Publisher American Physiological Sociely
Language eng
Subject C1
920111 Nervous System and Disorders
1109 Neurosciences
110601 Biomechanics
Abstract Studying the responsiveness of specific central nervous system pathways to electrical or magnetic stimulation can provide important information regarding fatigue processes in the central nervous system. We investigated the changes in corticospinal responsiveness during a sustained submaximal contraction of the triceps surae. Comparisons were made between the size of motor-evoked potentials (MEPs) elicited by motor cortical stimulation and cervicomedullary motor-evoked potentials (CMEPs) elicited by magnetic stimulation of the descending tracts to determine the site of any change in corticospinal responsiveness. Participants maintained an isometric contraction of triceps surae at 30% of maximal voluntary contraction (MVC) for as long as possible on two occasions. Stimulation was applied to the motor cortex or the cervicomedullary junction at 1-min intervals during contraction until task failure. Peripheral nerve stimulation was also applied to evoke maximal M waves (Mmax) and a superimposed twitch. Additionally, MEPs and CMEPs were evoked during brief contractions at 80%, 90%, and 100% of MVC as a nonfatigue control. During the sustained contractions, MEP amplitude increased significantly in soleus (113%) and medial gastrocnemius (108%) muscles and, at task failure, matched MEP amplitude in the prefatigue MVC (~20–25% Mmax). In contrast, CMEP amplitude increased significantly in medial gastrocnemius (51%), but not in soleus (63%) muscle and, at task failure, was significantly smaller than during prefatigue MVC (5–6% Mmax vs. 11–13% Mmax). The data indicate that cortical processes contribute substantially to the increase in corticospinal responsiveness during sustained submaximal contraction of triceps surae.
Keyword lower limb
central nervous system
transcranial magnetic stimulation
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

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Created: Thu, 03 Sep 2009, 17:53:32 EST by Mr Andrew Martlew on behalf of School of Human Movement and Nutrition Sciences