European Journal of Applied Physiology

, Volume 119, Issue 4, pp 991–1005 | Cite as

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

  • Jeanne DekerleEmail author
  • P. Ansdell
  • L. Schäfer
  • A. Greenhouse-Tucknott
  • J. Wrightson
Original Article



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]).


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.


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.


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.


Neuromuscular fatigue Central fatigue Exercise Isometric contraction Isokinetic dynanometer 



Estimated resting twitch


Intraclass correlation


Knee extensors


Motor evoked potential


Maximal voluntary contractions


Neuromuscular assessment


Potentiated twitch force


Smallest detectable change


Superimposed twitch


Superimposed twitch during a maximal voluntary contraction


Transcranial magnetic stimulation


Voluntary activation


Voluntary activation using transcranial magnetic stimulation


Voluntary contraction



The authors thank Dr. Rosie Twomey and Prof. Guillaume Millet for the valuable critical review of our manuscript.

Author contribution statement

All authors contributed to the conception and design of the study. PA, AGT, JW, LS collected the data. All authors were involved in the analysis and interpretation of the data. JD, AGT and PA wrote the manuscript. All authors reviewed and approved the final version of the manuscript.


No external funding was received for this work.

Compliance with ethical standards

Conflict of interest

The authors report no conflict of interest for this work.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Fatigue and Exercise Laboratory, Centre for Sport and Exercise Science and Medicine (SESAME)University of BrightonEastbourneUK
  2. 2.Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life SciencesNorthumbria UniversityNorthumbriaUK
  3. 3.Human Performance Laboratory, Faculty of KinesiologyUniversity of CalgaryCalgaryCanada

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