Cortical and spinal excitability during and after lengthening contractions of the human plantar flexor muscles performed with maximal voluntary effort

Hahn, Daniel and Hoffman, Ben W. ORCID: https://orcid.org/0000-0002-8408-6192 and Carroll, Timothy J. and Cresswell, Andrew G. (2012) Cortical and spinal excitability during and after lengthening contractions of the human plantar flexor muscles performed with maximal voluntary effort. PLoS One, 7 (11):e49907. pp. 1-9.

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Abstract

This study was designed to investigate the sites of potential specific modulations in the neural control of lengthening and subsequent isometric maximal voluntary contractions (MVCs) versus purely isometric MVCs of the plantar flexor muscles, when there is enhanced torque during and following stretch. Ankle joint torque during maximum voluntary plantar flexion was measured by a dynamometer when subjects (n = 10) lay prone on a bench with the right ankle tightly strapped to a foot-plate. Neural control was analysed by comparing soleus motor responses to electrical nerve stimulation (M-wave, V-wave), electrical stimulation of the cervicomedullary junction (CMEP) and transcranial magnetic stimulation of the motor cortex (MEP). Enhanced torque of 17 ± 8% and 9 ± 8% was found during and 2.5-3 s after lengthening MVCs, respectively. Cortical and spinal responsiveness was similar to that in isometric conditions during the lengthening MVCs, as shown by unchanged MEPs, CMEPs and V-waves, suggesting that the major voluntary motor pathways are not subject to substantial inhibition. Following the lengthening MVCs, enhanced torque was accompanied by larger MEPs (p ≤ 0.05) and a trend to greater V-waves (p ≤ 0.1). In combination with stable CMEPs, increased MEPs suggest an increase in cortical excitability, and enlarged V-waves indicate greater motoneuronal output or increased stretch reflex excitability. The new results illustrate that neuromotor pathways are altered after lengthening MVCs suggesting that the underlying mechanisms of the enhanced torque are not purely mechanical in nature.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Copyright: c2012 Hahn et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 03 Sep 2021 04:57
Last Modified: 03 Sep 2021 04:59
Fields of Research (2008): 11 Medical and Health Sciences > 1106 Human Movement and Sports Science > 110603 Motor Control
Fields of Research (2020): 42 HEALTH SCIENCES > 4207 Sports science and exercise > 420703 Motor control
Identification Number or DOI: https://doi.org/10.1371/journal.pone.0049907
URI: http://eprints.usq.edu.au/id/eprint/42106

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