Neuromuscular Fatigue during Prolonged Exercise in Hypoxia

Jubeau, Marc, Rupp, Thomas, Temesi, John, Perrey, Stéphane, Wuyam, Bernard, Millet, Guillaume and Verges, Samuel (2017) Neuromuscular Fatigue during Prolonged Exercise in Hypoxia. Medicine & Science in Sports & Exercise, 49 (3). pp. 430-439. ISSN 0195-9131

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Abstract

Purpose:
Prolonged cycling exercise performance in normoxia is limited because of both peripheral and central neuromuscular impairments. It has been reported that cerebral perturbations are greater during short-duration exercise in hypoxia compared with normoxia. The purpose of this study was to test the hypothesis that central deficits are accentuated in hypoxia compared with normoxia during prolonged (three bouts of 80 min separated by 25 min) whole-body exercise at the same relative intensity.

Methods:
Ten subjects performed two sessions consisting of three 80-min cycling bouts at 45% of their relative maximal aerobic power in normoxia and hypoxia (FiO 2 = 0.12). Before exercise and after each bout, maximal voluntary force, voluntary activation assessed with nerve stimulation and transcranial magnetic stimulation, corticospinal excitability (motor evoked potential), intracortical inhibition (cortical silent period), and electrical (M-wave) and contractile (twitch and doublet peak forces) properties of the knee extensors were measured. Prefrontal and motor cortical oxygenation was also recorded during each cycling bout in both conditions.

Results:
A significant but similar force reduction (≈-22%) was observed at the end of exercise in normoxia and hypoxia. The modifications of voluntary activation assessed with transcranial magnetic stimulation and nerve stimulation, motor evoked potential, cortical silent period, and M-wave were also similar in both conditions. However, cerebral oxygenation was reduced in hypoxia compared with normoxia.

Conclusion:
These findings show that when performed at the same relative low intensity, prolonged exercise does not induce greater supraspinal fatigue in hypoxia compared with normoxia. Despite lower absolute exercise intensities in hypoxia, reduced brain O2 availability might contribute to similar amounts of central fatigue compared with normoxia.

Item Type:	Article
Uncontrolled Keywords:	Cortical voluntary activation, transcranial magnetic stimulation, brain oxygenation, knee extensors
Subjects:	C600 Sports Science
Department:	Faculties > Health and Life Sciences > Sport, Exercise and Rehabilitation
Depositing User:	Paul Burns
Date Deposited:	13 Sep 2018 14:42
Last Modified:	11 Oct 2019 19:15
URI:	http://nrl.northumbria.ac.uk/id/eprint/35700

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