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Severe hypoxia affects exercise performance independently of afferent feedback and peripheral fatigue

Journal of applied physiology (1985), 2012-04, Vol.112 (8), p.1335-1344 [Peer Reviewed Journal]

Copyright American Physiological Society Apr 15, 2012 ;Distributed under a Creative Commons Attribution 4.0 International License ;ISSN: 8750-7587 ;EISSN: 1522-1601 ;DOI: 10.1152/japplphysiol.00804.2011 ;PMID: 22323647

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Title:
Severe hypoxia affects exercise performance independently of afferent feedback and peripheral fatigue
Author: Millet, Guillaume Y ; Muthalib, Makii ; Jubeau, Marc ; Laursen, Paul B ; Nosaka, Kazunori
Subjects: Adult ; Adult Afferent Pathways / physiology Electric Stimulation Evoked Potentials, Motor / physiology Exercise / physiology Feedback, Physiological / physiology Humans Hypoxia / physiopathology Male Motor Cortex / physiology Muscle Contraction / physiology Muscle Fatigue / physiology Muscle, Skeletal / innervation Muscle, Skeletal / physiology Oxygen / metabolism Peripheral Nervous System / physiology Physical Endurance / physiology ; Afferent Pathways - physiology ; Brain ; Electric Stimulation ; Evoked Potentials, Motor - physiology ; Exercise ; Exercise - physiology ; Feedback, Physiological - physiology ; Humans ; Hypoxia ; Hypoxia - physiopathology ; Life Sciences ; Male ; Motor Cortex - physiology ; Muscle Contraction - physiology ; Muscle Fatigue - physiology ; Muscle, Skeletal - innervation ; Muscle, Skeletal - physiology ; Muscular system ; Oxygen ; Oxygen - metabolism ; Peripheral Nervous System - physiology ; Physical Endurance - physiology
Is Part Of: Journal of applied physiology (1985), 2012-04, Vol.112 (8), p.1335-1344
Description: To test the hypothesis that hypoxia centrally affects performance independently of afferent feedback and peripheral fatigue, we conducted two experiments under complete vascular occlusion of the exercising muscle under different systemic O(2) environmental conditions. In experiment 1, 12 subjects performed repeated submaximal isometric contractions of the elbow flexor to exhaustion (RCTE) with inspired O(2) fraction fixed at 9% (severe hypoxia, SevHyp), 14% (moderate hypoxia, ModHyp), 21% (normoxia, Norm), or 30% (hyperoxia, Hyper). The number of contractions (performance), muscle (biceps brachii), and prefrontal near-infrared spectroscopy (NIRS) parameters and high-frequency paired-pulse (PS100) evoked responses to electrical muscle stimulation were monitored. In experiment 2, 10 subjects performed another RCTE in SevHyp and Norm conditions in which the number of contractions, biceps brachii electromyography responses to electrical nerve stimulation (M wave), and transcranial magnetic stimulation responses (motor-evoked potentials, MEP, and cortical silent period, CSP) were recorded. Performance during RCTE was significantly reduced by 10-15% in SevHyp (arterial O(2) saturation, SpO(2) = ∼75%) compared with ModHyp (SpO(2) = ∼90%) or Norm/Hyper (SpO(2) > 97%). Performance reduction in SevHyp occurred despite similar 1) metabolic (muscle NIRS parameters) and functional (changes in PS100 and M wave) muscle states and 2) MEP and CSP responses, suggesting comparable corticospinal excitability and spinal and cortical inhibition between SevHyp and Norm. It is concluded that, in SevHyp, performance and central drive can be altered independently of afferent feedback and peripheral fatigue. It is concluded that submaximal performance in SevHyp is partly reduced by a mechanism related directly to brain oxygenation.
Publisher: United States: American Physiological Society
Language: English
Identifier: ISSN: 8750-7587
EISSN: 1522-1601
DOI: 10.1152/japplphysiol.00804.2011
PMID: 22323647
Source: Geneva Foundation Free Medical Journals at publisher websites
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Severe hypoxia affects exercise performance independently of afferent feedback and peripheral fatigue

Copyright American Physiological Society Apr 15, 2012 ;Distributed under a Creative Commons Attribution 4.0 International License ;ISSN: 8750-7587 ;EISSN: 1522-1601 ;DOI: 10.1152/japplphysiol.00804.2011 ;PMID: 22323647

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