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Front. Physiol. | doi: 10.3389/fphys.2018.00962

Hypoxia and fatigue impair rapid torque development of knee extensors in elite alpine skiers

Marine Alhammoud1, 2,  Baptiste Morel3,  Olivier Girard4, 5,  Violaine Sevrez6, Alexandre Germain7, Thomas Chamu7,  Sebastien Racinais4, 8* and  Christophe Hautier1
  • 1Inter-university Laboratory of Human Movement Biology, Université de Lyon, France
  • 2Fédération Française de Ski, France
  • 3Laboratory “Movement, Interactions, Performance”, University of Maine, France
  • 4Athlete Health and Performance, Aspetar Hospital, Qatar
  • 5School of Psychology and Exercise Science, Murdoch University, Australia
  • 6CNRS, ISM, Aix-Marseille Université, France
  • 7Orthopedic and Sports Medicine Hospital La Sauvegarde, France
  • 8Institut national du sport, de l'expertise et de la performance, France

This study examined the effects of acute hypoxia on maximal and explosive torque and fatigability in knee extensors of skiers. Twenty-two elite male alpine skiers performed 35 maximal, repeated isokinetic knee extensions at 180°·s-1 (total exercise duration 61.25 s) in normoxia (NOR, FiO2 0.21) and normobaric hypoxia (HYP, FiO2 0.13) in a randomized, single-blind design. Peak torque and rate of torque development (RTD) from 0 to 100 ms and associated Vastus Lateralis peak EMG activity and rate of EMG rise (RER) were determined for each contraction. Relative changes in deoxyhemoglobin concentration of the VL muscle were monitored by near-infrared spectroscopy. Peak torque and peak EMG activity did not differ between conditions and decreased similarly with fatigue (p<0.001), with peak torque decreasing continuously but EMG activity decreasing significantly after 30 contractions only. Compared to NOR, RTD and RER values were lower in HYP during the first 12 and 9 contractions respectively (both p<0.05). Deoxyhemoglobin concentration during the last five contractions was higher in HYP than NOR (p=0.050) but the delta between maximal and minimal deoxyhemoglobin for each contraction was similar in HYP and NOR suggesting a similar muscle O2 utilization. Post exercise heart rate (138±24 bpm) and blood lactate concentration (5.8±3.1 mmol.l-1) did not differ between conditions. Arterial oxygen saturation was significantly lower (84±4 vs. 98±1%, p<0.001) and ratings of perceived exertion higher (6±1 vs. 5±1, p<0.001) in HYP than NOR. In summary, hypoxia limits RTD via a decrease in neural drive in elite alpine skiers undertaking maximal repeated isokinetic knee extensions, but the effect of hypoxic exposure is negated as fatigue develops. Isokinetic testing protocols for elite alpine skiers should incorporate RTD and rate of EMG rise measurements as they display a higher sensitivity than peak torque and EMG activity.

Keywords: repeated knee extensions, Simulated altitude, maximal torque production, neural drive, Isokinetic, near-infrared spectroscopy

Received: 25 May 2018; Accepted: 29 Jun 2018.

Edited by:

Gianluca Vernillo, Università degli Studi di Milano, Italy

Reviewed by:

Tadej Debevec, Faculty of Sport, University of Ljubljana, Slovenia
Stuart Goodall, Northumbria University, United Kingdom
Martin Burtscher, Universität Innsbruck, Austria  

Copyright: © 2018 Alhammoud, Morel, Girard, Sevrez, Germain, Chamu, Racinais 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. Sebastien Racinais, Aspetar Hospital, Athlete Health and Performance, Doha, Qatar, sebastien.racinais@aspetar.com