Inter-muscle differences in modulation of motor evoked potentials and posterior root-muscle reflexes evoked from lower-l
- PDF / 1,236,578 Bytes
- 12 Pages / 595.276 x 790.866 pts Page_size
- 86 Downloads / 195 Views
RESEARCH ARTICLE
Inter‑muscle differences in modulation of motor evoked potentials and posterior root‑muscle reflexes evoked from lower‑limb muscles during agonist and antagonist muscle contractions Akira Saito1,2,3 · Kento Nakagawa4 · Yohei Masugi2,5 · Kimitaka Nakazawa2 Received: 17 August 2020 / Accepted: 28 October 2020 © The Author(s) 2020
Abstract Voluntary contraction facilitates corticospinal and spinal reflex circuit excitabilities of the contracted muscle and inhibits spinal reflex circuit excitability of the antagonist. It has been suggested that modulation of spinal reflex circuit excitability in agonist and antagonist muscles during voluntary contraction differs among lower-limb muscles. However, whether the effects of voluntary contraction on the excitabilities of corticospinal and spinal reflex circuits depend on the tested muscles remains unknown. The purpose of this study was to examine inter-muscle differences in modulation of the corticospinal and spinal reflex circuit excitabilities of multiple lower-limb muscles during voluntary contraction. Eleven young males performed isometric plantar-flexion, dorsi-flexion, knee extension, and flexion at low torque levels. Motor evoked potentials (MEPs) and posterior root-muscle reflexes from seven lower-leg and thigh muscles were evoked by transcranial magnetic stimulation and transcutaneous spinal cord stimulation, respectively, at rest and during weak voluntary contractions. MEP and posterior root-muscle reflex amplitudes of agonists were significantly increased as agonist torque level increased, except for the reflex of the tibialis anterior. MEP amplitudes of antagonists were significantly increased in relation to the agonist torque level, but those of the rectus femoris were slightly depressed during knee flexion. Regarding the posterior root-muscle reflex of the antagonists, the amplitudes of triceps surae and the hamstrings were significantly decreased, but those of the quadriceps femoris were significantly increased as the agonist torque level increased. These results demonstrate that modulation of corticospinal and spinal reflex circuit excitabilities during agonist and antagonist muscle contractions differed among lower-limb muscles. Keywords Corticospinal excitability · Posterior root-muscle reflex · Electromyography · Quadriceps femoris · Spinal cord stimulation
Introduction
Communicated by Sreedharan Sajikumar. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00221-020-05973-x) contains supplementary material, which is available to authorized users. * Akira Saito [email protected]‑u.ac.jp 1
Center for Health and Sports Science, Kyushu Sangyo University, Matsukadai, Higashi‑ku, Fukuoka, Japan
Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro‑ku, Tokyo, Japan
2
Voluntary muscle contraction facilitates the excitability of corticospinal tract and spinal reflex circuits of the contracted muscle. Modulations of corticospinal tract and spinal reflex circuit e
Data Loading...
