Increases in corticospinal responsiveness during a sustained submaximal plantar flexion

Hoffman, B. W. ORCID: https://orcid.org/0000-0002-8408-6192 and Oya, T. and Carroll, T. J. and Cresswell, A. G. (2009) Increases in corticospinal responsiveness during a sustained submaximal plantar flexion. Journal of Applied Physiology, 107 (1). pp. 112-120. ISSN 8750-7587


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 (M-max) 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 (similar to 20-25% M-max). 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% M-max vs. 11-13% M-max). The data indicate that cortical processes contribute substantially to the increase in corticospinal responsiveness during sustained submaximal contraction of triceps surae.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Permanent restricted access to Published version in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 03 Sep 2021 04:42
Last Modified: 03 Sep 2021 04:45
Uncontrolled Keywords: lower limb; central nervous system; muscle; transcranial magnetic stimulation; electromyogram
Fields of Research (2008): 11 Medical and Health Sciences > 1106 Human Movement and Sports Science > 110603 Motor Control
11 Medical and Health Sciences > 1106 Human Movement and Sports Science > 110601 Biomechanics
Fields of Research (2020): 42 HEALTH SCIENCES > 4207 Sports science and exercise > 420701 Biomechanics
42 HEALTH SCIENCES > 4207 Sports science and exercise > 420703 Motor control
Identification Number or DOI: https://doi.org/10.1152/japplphysiol.91541.2008
URI: http://eprints.usq.edu.au/id/eprint/42108

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