Cortical and segmental excitability during fatiguing contractions of the soleus muscle in humans

Masaki Iguchi; Richard K Shields

doi:10.1016/j.clinph.2011.06.031

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Cortical and segmental excitability during fatiguing contractions of the soleus muscle in humans

Journal article

Open access

Peer reviewed

Cortical and segmental excitability during fatiguing contractions of the soleus muscle in humans

Masaki Iguchi and Richard K Shields

Clinical neurophysiology, Vol.123(2), pp.335-343

02/2012

DOI: 10.1016/j.clinph.2011.06.031

PMCID: PMC3654395

PMID: 21802985

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https://www.ncbi.nlm.nih.gov/pmc/articles/3654395View

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Abstract

The aim of this study was to examine the cortical and segmental excitability changes during fatigue of the soleus muscle. Ten healthy young subjects performed 45 plantar flexion maximal voluntary contractions (MVCs) (7-s on/3-s off) in 9 epochs of five contractions. Motor evoked potentials (MEPs) using transcranial magnetic stimulation and H-reflexes were assessed during the task. The torque and the soleus EMG activity both showed the greatest decline during the 1st epoch, followed by a gradual, but significant decrease by the end of the task (∼70% pre-fatigue). The H-reflex sampled at rest after each epoch decreased to 66.6±18.3% pre-fatigue after the first epoch, and then showed no further change. The MEP on 10% pre-fatigue MVC after each epoch increased progressively (252.9±124.2% pre-fatigue). There was no change in the MEPs on the 3rd MVC in each epoch. The silent period on the MVC increased (109.0±9.2% pre-fatigue) early with no further changes during the task. These findings support that the motor cortex increases excitability during fatigue, but with a concomitant inhibition. These findings are in contrast to upper extremity muscles and may reflect a distinct response specific to postural, fatigue-resistant muscle.

H-Reflex - physiology

Young Adult

Motor Cortex - physiology

Evoked Potentials, Motor - physiology

Humans

Muscle Contraction - physiology

Adult

Female

Male

Muscle, Skeletal - physiology

Muscle Fatigue - physiology

Details

Title: Subtitle: Cortical and segmental excitability during fatiguing contractions of the soleus muscle in humans
Creators: Masaki Iguchi - Physical Therapy and Rehabilitation Science, The University of Iowa, 1-252 Medical Education Bldg., Iowa City, IA 52242-1190, USA
Richard K Shields
Resource Type: Journal article
Publication Details: Clinical neurophysiology, Vol.123(2), pp.335-343
DOI: 10.1016/j.clinph.2011.06.031
PMID: 21802985
PMCID: PMC3654395
NLM abbreviation: Clin Neurophysiol
ISSN: 1388-2457
eISSN: 1872-8952
Publisher: Netherlands
Grant note: R01 NR010285 / NINR NIH HHS R01 HD062507 / NICHD NIH HHS
Language: English
Date published: 02/2012
Academic Unit: Orthopedics and Rehabilitation; Physical Therapy and Rehabilitation Science
Record Identifier: 9984047983202771

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