Mathieu Marillier1,2, Pierrick J Arnal3, Thibault Le Roux Mallouf1,2, Thomas Rupp1,2,4, Guillaume Y Millet1,2,3,5, Samuel Verges6,7. 1. U1042, INSERM, Batiment Jean Roget, Faculté de Médecine, La Tronche Cedex, France. 2. Laboratoire HP2 (U1042 INSERM), Batiment Jean Roget, Faculté de Médecine, UM Sports Pathologies, Hôpital Sud, Grenoble Alpes University, Avenue Kimberley, 38 434, Echirolles, France. 3. Inter-University Laboratory of Human Movement Biology, University of Lyon, University Saint Etienne, Saint-Étienne, France. 4. Inter-University Laboratory of Human Movement Biology, University Savoie Mont Blanc, Chambéry, France. 5. Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada. 6. U1042, INSERM, Batiment Jean Roget, Faculté de Médecine, La Tronche Cedex, France. sverges@chu-grenoble.fr. 7. Laboratoire HP2 (U1042 INSERM), Batiment Jean Roget, Faculté de Médecine, UM Sports Pathologies, Hôpital Sud, Grenoble Alpes University, Avenue Kimberley, 38 434, Echirolles, France. sverges@chu-grenoble.fr.
Abstract
PURPOSE: While acute hypoxic exposure enhances exercise-induced central fatigue and can alter corticospinal excitability and inhibition, the effect of prolonged hypoxic exposure on these parameters remains to be clarified. We hypothesized that 5 days of altitude exposure would (i) normalize exercise-induced supraspinal fatigue during isolated muscle exercise to sea level (SL) values and (ii) increase corticospinal excitability and inhibition. METHODS: Eleven male subjects performed intermittent isometric elbow flexions at 50% of maximal voluntary contraction to task failure at SL and after 1 (D1) and 5 (D5) days at 4350 m. Transcranial magnetic stimulation and peripheral electrical stimulation were used to assess supraspinal and peripheral fatigues. Pre-frontal cortex and biceps brachii oxygenation was monitored by near-infrared spectroscopy. RESULTS: Exercise duration was not statistically different between SL (1095 ± 562 s), D1 (1132 ± 516 s), and D5 (1440 ± 689 s). No significant differences were found between the three experimental conditions in maximal voluntary activation declines at task failure (SL -16.8 ± 9.5%; D1 -25.5 ± 11.2%; D5 -21.8 ± 7.0%; p > 0.05). Exercise-induced peripheral fatigue was larger at D5 versus SL (100 Hz doublet at task failure: -58.8 ± 16.6 versus -41.8 ± 20.1%; p < 0.05). Corticospinal excitability at 50% maximal voluntary contraction was lower at D5 versus SL (brachioradialis p < 0.05, biceps brachii p = 0.055). Cortical silent periods were shorter at SL versus D1 and D5 (p < 0.05). CONCLUSIONS: The present results show similar patterns of supraspinal fatigue development during isometric elbow flexions at SL and after 1 and 5 days at high altitude, despite larger amount of peripheral fatigue at D5, lowered corticospinal excitability and enhanced corticospinal inhibition at altitude.
PURPOSE: While acute hypoxic exposure enhances exercise-induced central fatigue and can alter corticospinal excitability and inhibition, the effect of prolonged hypoxic exposure on these parameters remains to be clarified. We hypothesized that 5 days of altitude exposure would (i) normalize exercise-induced supraspinal fatigue during isolated muscle exercise to sea level (SL) values and (ii) increase corticospinal excitability and inhibition. METHODS: Eleven male subjects performed intermittent isometric elbow flexions at 50% of maximal voluntary contraction to task failure at SL and after 1 (D1) and 5 (D5) days at 4350 m. Transcranial magnetic stimulation and peripheral electrical stimulation were used to assess supraspinal and peripheral fatigues. Pre-frontal cortex and biceps brachii oxygenation was monitored by near-infrared spectroscopy. RESULTS: Exercise duration was not statistically different between SL (1095 ± 562 s), D1 (1132 ± 516 s), and D5 (1440 ± 689 s). No significant differences were found between the three experimental conditions in maximal voluntary activation declines at task failure (SL -16.8 ± 9.5%; D1 -25.5 ± 11.2%; D5 -21.8 ± 7.0%; p > 0.05). Exercise-induced peripheral fatigue was larger at D5 versus SL (100 Hz doublet at task failure: -58.8 ± 16.6 versus -41.8 ± 20.1%; p < 0.05). Corticospinal excitability at 50% maximal voluntary contraction was lower at D5 versus SL (brachioradialis p < 0.05, biceps brachii p = 0.055). Cortical silent periods were shorter at SL versus D1 and D5 (p < 0.05). CONCLUSIONS: The present results show similar patterns of supraspinal fatigue development during isometric elbow flexions at SL and after 1 and 5 days at high altitude, despite larger amount of peripheral fatigue at D5, lowered corticospinal excitability and enhanced corticospinal inhibition at altitude.
Entities:
Keywords:
Central fatigue; Exercise; Hypoxia; Neuromuscular fatigue
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