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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Physiol. | doi: 10.3389/fphys.2019.00875


  • 1EA 4334 Laboratoire Motricité, Interaction, Performance, Université du Maine, France
  • 2EA7424 Laboratoire Interuniversitaire de Biologie de la Motricité, Université Claude Bernard Lyon 1, France

During high intensity exercise, metabosensitive muscle afferents are thought to inhibit the motor drive command to restrict the level of peripheral fatigue to an individual’s critical threshold. No evidence exists of an individual relationship between peripheral fatigue and the decrease in voluntary activation reached after prolonged all-out exercise. Moreover, there is no explanation for the previously reported large decrease in voluntary activation despite low metabolic stress during high force contractions. Thirteen active men completed two maximal intensity isokinetic knee extension tests (160 contractions) under conditions of low force - high velocity and high force – low velocity. Neuromuscular testing including maximal torque, evoked torque and voluntary activation, was done every 20 contractions. The exponential modeling of these variables over time allowed us to predict the stable state (asymptote) and the rate of decrease (curvature constant). For both high and low force contractions the evoked torque and voluntary activation asymptotes were negatively correlated (R²=0.49 and R² = 0.46, respectively). The evoked torque asymptotes of the high and low force conditions were positively correlated (R²=0.49). For the high force contractions, the evoked torque and voluntary activation curvature constant were negatively correlated (R²=0.43). These results support the idea that a restrained central motor drive keeps peripheral fatigue under this threshold. Furthermore, an individual would show similar fatigue sensibility regardless of the force generated. These data also suggest that the decrease in voluntary activation might not have been triggered by peripheral perturbations during the first high force contractions.

Keywords: Evoked torque, voluntary activation, group III/IV muscle afferents, Knee extensors, Neuromuscular fatigue

Received: 06 Nov 2018; Accepted: 21 Jun 2019.

Edited by:

Trevor C. Chen, National Taiwan Normal University, Taiwan

Reviewed by:

Ya-Ju Chang, Chang Gung University, Taiwan
Xin Ye, University of Mississippi, United States  

Copyright: © 2019 Morel, Lapole, Liotard and Hautier. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Baptiste Morel, EA 4334 Laboratoire Motricité, Interaction, Performance, Université du Maine, Le Mans, France,