Hypoxia and Fatigue Impair Rapid Torque Development of Knee Extensors in Elite Alpine Skiers
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 n...
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doaj-668a08f3b24a4fffbbe6b2c5c071d24d2020-11-24T21:19:06ZengFrontiers Media S.A.Frontiers in Physiology1664-042X2018-07-01910.3389/fphys.2018.00962400875Hypoxia and Fatigue Impair Rapid Torque Development of Knee Extensors in Elite Alpine SkiersMarine Alhammoud0Marine Alhammoud1Baptiste Morel2Olivier Girard3Olivier Girard4Sebastien Racinais5Sebastien Racinais6Violaine Sevrez7Alexandre Germain8Thomas Chamu9Christophe Hautier10Inter-university Laboratory of Human Movement Biology (EA 7424), Claude Bernard University Lyon 1, Lyon, FranceFrench Ski Federation, Annecy, FranceLaboratory “Movement, Interactions, Performance” (EA 4334), Le Mans University, Le Mans, FranceSchool of Psychology and Exercise Science, Murdoch University, Perth, WA, AustraliaAthlete Health and Performance Research Centre, Aspetar Orthopedic and Sports Medicine Hospital, Doha, QatarAthlete Health and Performance Research Centre, Aspetar Orthopedic and Sports Medicine Hospital, Doha, QatarLaboratory Sport, Expertise and Performance, French Institute of Sport (INSEP), Paris, FranceFrench National Center for Scientific Research, Institute of Movement Sciences, Aix-Marseille University, Marseille, FranceOrthopedic and Sports Medicine Hospital La Sauvegarde, Lyon, FranceOrthopedic and Sports Medicine Hospital La Sauvegarde, Lyon, FranceInter-university Laboratory of Human Movement Biology (EA 7424), Claude Bernard University Lyon 1, Lyon, FranceThis 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 RER measurements as they display a higher sensitivity than peak torque and EMG activity.https://www.frontiersin.org/article/10.3389/fphys.2018.00962/fullisokineticmaximal torque productionnear-infrared spectroscopyneural driverepeated knee extensionssimulated altitude |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Marine Alhammoud Marine Alhammoud Baptiste Morel Olivier Girard Olivier Girard Sebastien Racinais Sebastien Racinais Violaine Sevrez Alexandre Germain Thomas Chamu Christophe Hautier |
spellingShingle |
Marine Alhammoud Marine Alhammoud Baptiste Morel Olivier Girard Olivier Girard Sebastien Racinais Sebastien Racinais Violaine Sevrez Alexandre Germain Thomas Chamu Christophe Hautier Hypoxia and Fatigue Impair Rapid Torque Development of Knee Extensors in Elite Alpine Skiers Frontiers in Physiology isokinetic maximal torque production near-infrared spectroscopy neural drive repeated knee extensions simulated altitude |
author_facet |
Marine Alhammoud Marine Alhammoud Baptiste Morel Olivier Girard Olivier Girard Sebastien Racinais Sebastien Racinais Violaine Sevrez Alexandre Germain Thomas Chamu Christophe Hautier |
author_sort |
Marine Alhammoud |
title |
Hypoxia and Fatigue Impair Rapid Torque Development of Knee Extensors in Elite Alpine Skiers |
title_short |
Hypoxia and Fatigue Impair Rapid Torque Development of Knee Extensors in Elite Alpine Skiers |
title_full |
Hypoxia and Fatigue Impair Rapid Torque Development of Knee Extensors in Elite Alpine Skiers |
title_fullStr |
Hypoxia and Fatigue Impair Rapid Torque Development of Knee Extensors in Elite Alpine Skiers |
title_full_unstemmed |
Hypoxia and Fatigue Impair Rapid Torque Development of Knee Extensors in Elite Alpine Skiers |
title_sort |
hypoxia and fatigue impair rapid torque development of knee extensors in elite alpine skiers |
publisher |
Frontiers Media S.A. |
series |
Frontiers in Physiology |
issn |
1664-042X |
publishDate |
2018-07-01 |
description |
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 RER measurements as they display a higher sensitivity than peak torque and EMG activity. |
topic |
isokinetic maximal torque production near-infrared spectroscopy neural drive repeated knee extensions simulated altitude |
url |
https://www.frontiersin.org/article/10.3389/fphys.2018.00962/full |
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