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

Oya, T. and Hoffman, B. W. ORCID: https://orcid.org/0000-0002-8408-6192 and Cresswell, A. G. (2008) Corticospinal-evoked responses in lower limb muscles during voluntary contractions at varying strengths. Journal of Applied Physiology, 105 (5). pp. 1527-1532. ISSN 8750-7587


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 similar 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 (M-max)] showed an increase, followed by a plateau, over the greater part of the contraction range with responses increasing from similar to 0.2 to similar to 6% of M-max for Sol and from similar to 0.3 to similar to 10% of M-max 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.


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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 03:12
Last Modified: 03 Sep 2021 04:35
Uncontrolled Keywords: transcranial magnetic stimulation; electromyography; motor system
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.90586.2008
URI: http://eprints.usq.edu.au/id/eprint/42109

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