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Published in: European Journal of Applied Physiology 4/2019

01-04-2019 | Motor Evoked Potential | Original Article

Methodological issues with the assessment of voluntary activation using transcranial magnetic stimulation in the knee extensors

Authors: Jeanne Dekerle, P. Ansdell, L. Schäfer, A. Greenhouse-Tucknott, J. Wrightson

Published in: European Journal of Applied Physiology | Issue 4/2019

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Abstract

Purpose

The assessment of voluntary activation of the knee extensors using transcranial magnetic stimulation (VATMS) is routinely performed to assess the supraspinal function. Yet methodological scrutiny of the technique is scarce. The aim of the present study was to examine face validity and reliability of VATMS and its two main determinants (superimposed twitch during a maximal voluntary contraction [SIT100%] and estimated resting twitch [ERT]).

Methods

SIT100%, ERT, and VATMS were measured on ten healthy males (age 24 ± 5 years) before and following intermittent isometric fatiguing exercise on two separate occasions.

Results

The findings indicated issues regarding the accuracy of ERT and suggested a three-point relationship should not be used to determine ERT. Reliabilities for VATMS, SIT100%, and ERT were acceptable pre- but much weaker post-exercise (especially for SIT100%). Despite statistically significant changes in main neuromuscular variables following the intermittent isometric fatiguing exercise (P < 0.05), when post-exercise reliability was considered, the exercise effect on VATMS was smaller than the smallest detectable change in 18 of the 20 individual tests performed, and for the whole sample for one of two visits. Finally, maximal voluntary contraction was reduced significantly following the neuromuscular assessment (NMA) pre-exercise but recovered during the NMA post-exercise.

Conclusion

This is the first study to demonstrate a lack of sensitivity of key neuromuscular measurements to exercise and to evidence both presence of neuromuscular fatigue following the NMA in itself, and recovery of the neuromuscular function during the NMA post-exercise. These results challenge the face validity of this routinely used protocol.
Literature
go back to reference Di Lazzaro V et al (1998) Effects of voluntary contraction on descending volleys evoked by transcranial stimulation in conscious humans. J Physiol 508(Pt 2):625–633CrossRefPubMedPubMedCentral Di Lazzaro V et al (1998) Effects of voluntary contraction on descending volleys evoked by transcranial stimulation in conscious humans. J Physiol 508(Pt 2):625–633CrossRefPubMedPubMedCentral
go back to reference Gandevia SC (2001) Spinal and supraspinal factors in human muscle fatigue. Physiol Rev 81:1725–1789CrossRefPubMed Gandevia SC (2001) Spinal and supraspinal factors in human muscle fatigue. Physiol Rev 81:1725–1789CrossRefPubMed
Metadata
Title
Methodological issues with the assessment of voluntary activation using transcranial magnetic stimulation in the knee extensors
Authors
Jeanne Dekerle
P. Ansdell
L. Schäfer
A. Greenhouse-Tucknott
J. Wrightson
Publication date
01-04-2019
Publisher
Springer Berlin Heidelberg
Published in
European Journal of Applied Physiology / Issue 4/2019
Print ISSN: 1439-6319
Electronic ISSN: 1439-6327
DOI
https://doi.org/10.1007/s00421-019-04089-7

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