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Unilateral grip fatigue reduces short interval intracortical inhibition in ipsilateral primary motor cortex.
Clin Neurophysiol. 2009 Jan; 120(1):198-203.CN

Abstract

OBJECTIVE

This study was designed to examine whether exhaustive grip exercise of the left hand affected intracortical excitability in ipsilateral motor cortex.

METHODS

Ten healthy male subjects (aged 21-24 years) participated in experiment 1 in which paired-pulse transcranial magnetic stimulation (TMS) was used to test corticospinal and corticocortical excitability in right (relaxed) first dorsal interosseous (FDI) muscle during the recovery period after exhaustive forceful grip exercise of the left hand. Seven of the same subjects participated in experiment 2, in which the intensity of the test stimulus was adjusted so that the amplitude of motor evoked potential (MEP(TEST)) was kept constant throughout the measurement.

RESULTS

In experiment 1, MEP(TEST) was slightly reduced from 5 to 15min after exercise whilst short interval intracortical inhibition (SICI) at interstimulus interval (ISI) of 2 and 3ms became less effective. Intracortical facilitation (ICF) was unchanged. In experiment 2 when the MEP(TEST) was maintained at a constant size there was again no change in ICF, and the reduction in SICI was still present at the same intervals.

CONCLUSIONS

We conclude that unilateral exhaustive grip exercise reduced the excitability of the corticospinal output of the ipsilateral motor cortex whilst simultaneously reducing the excitability of SICI. These results would be compatible with the idea that fatigue increases the tonic level of interhemispheric inhibition from the fatigued to the non-fatigued cortex.

SIGNIFICANCE

Muscle fatigue to the point of exhaustion has lasting effects on the excitability of intracortical circuits in the non-exercised hemisphere, perhaps via changes in the tonic levels of activity in transcallosal pathways.

Authors+Show Affiliations

Biological Functions and Engineering, Kyushu Institute of Technology, Kitakyushu, Japan.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

19028439

Citation

Takahashi, Kyohei, et al. "Unilateral Grip Fatigue Reduces Short Interval Intracortical Inhibition in Ipsilateral Primary Motor Cortex." Clinical Neurophysiology : Official Journal of the International Federation of Clinical Neurophysiology, vol. 120, no. 1, 2009, pp. 198-203.
Takahashi K, Maruyama A, Maeda M, et al. Unilateral grip fatigue reduces short interval intracortical inhibition in ipsilateral primary motor cortex. Clin Neurophysiol. 2009;120(1):198-203.
Takahashi, K., Maruyama, A., Maeda, M., Etoh, S., Hirakoba, K., Kawahira, K., & Rothwell, J. C. (2009). Unilateral grip fatigue reduces short interval intracortical inhibition in ipsilateral primary motor cortex. Clinical Neurophysiology : Official Journal of the International Federation of Clinical Neurophysiology, 120(1), 198-203. https://doi.org/10.1016/j.clinph.2008.10.003
Takahashi K, et al. Unilateral Grip Fatigue Reduces Short Interval Intracortical Inhibition in Ipsilateral Primary Motor Cortex. Clin Neurophysiol. 2009;120(1):198-203. PubMed PMID: 19028439.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Unilateral grip fatigue reduces short interval intracortical inhibition in ipsilateral primary motor cortex. AU - Takahashi,Kyohei, AU - Maruyama,Atsuo, AU - Maeda,Masato, AU - Etoh,Seiji, AU - Hirakoba,Kohji, AU - Kawahira,Kazumi, AU - Rothwell,John C, Y1 - 2008/11/22/ PY - 2008/06/19/received PY - 2008/09/16/revised PY - 2008/10/02/accepted PY - 2008/11/26/pubmed PY - 2009/4/9/medline PY - 2008/11/26/entrez SP - 198 EP - 203 JF - Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology JO - Clin Neurophysiol VL - 120 IS - 1 N2 - OBJECTIVE: This study was designed to examine whether exhaustive grip exercise of the left hand affected intracortical excitability in ipsilateral motor cortex. METHODS: Ten healthy male subjects (aged 21-24 years) participated in experiment 1 in which paired-pulse transcranial magnetic stimulation (TMS) was used to test corticospinal and corticocortical excitability in right (relaxed) first dorsal interosseous (FDI) muscle during the recovery period after exhaustive forceful grip exercise of the left hand. Seven of the same subjects participated in experiment 2, in which the intensity of the test stimulus was adjusted so that the amplitude of motor evoked potential (MEP(TEST)) was kept constant throughout the measurement. RESULTS: In experiment 1, MEP(TEST) was slightly reduced from 5 to 15min after exercise whilst short interval intracortical inhibition (SICI) at interstimulus interval (ISI) of 2 and 3ms became less effective. Intracortical facilitation (ICF) was unchanged. In experiment 2 when the MEP(TEST) was maintained at a constant size there was again no change in ICF, and the reduction in SICI was still present at the same intervals. CONCLUSIONS: We conclude that unilateral exhaustive grip exercise reduced the excitability of the corticospinal output of the ipsilateral motor cortex whilst simultaneously reducing the excitability of SICI. These results would be compatible with the idea that fatigue increases the tonic level of interhemispheric inhibition from the fatigued to the non-fatigued cortex. SIGNIFICANCE: Muscle fatigue to the point of exhaustion has lasting effects on the excitability of intracortical circuits in the non-exercised hemisphere, perhaps via changes in the tonic levels of activity in transcallosal pathways. SN - 1872-8952 UR - https://www.unboundmedicine.com/medline/citation/19028439/Unilateral_grip_fatigue_reduces_short_interval_intracortical_inhibition_in_ipsilateral_primary_motor_cortex_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S1388-2457(08)01009-2 DB - PRIME DP - Unbound Medicine ER -