| Dietary nitrate improves muscle but not cerebral oxygenation status during exercise in hypoxia. | |
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MedLine Citation:
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PMID: 22773768 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Introduction: Exercise tolerance is impaired in hypoxia and it has recently been shown that dietary nitrate supplementation can reduce the oxygen cost of muscle contractions. Therefore we investigated the effect of dietary nitrate supplementation on arterial, muscle and cerebral oxygenation status, symptoms of acute mountain sickness (AMS), and exercise tolerance in simulated 5000m altitude. Methods: Fitftheen young healthy volunteers participated in three experimental sessions according to a cross-over study design. From 6 days prior to each session subjects received either beetroot juice delivering 0.07 mmol nitrate per kg b.w. per day (BR) or a control drink (CON). One session was in normoxia with CON (NOR(CON)). The two other sessions were in hypoxia (11% O(2)), with either CON (HYP(CON)) or BR (HYP(BR)). Subjects first cycled for 20 min @ 45% of peak VO(2) (EX(45%)) and thereafter performed a maximal incremental exercise test (EX(max)). Whole body VO(2), %SpO(2) via pulsoximetry, and muscle (TOI(M)) and cerebral (TOI(C)) oxygenation status by near-infrared spectroscopy, were measured. Results: Hypoxia per se substantially reduced VO(2)peak, %SpO(2), TOI(M) and TOI(C) (NOR(CON) vs. HYP(CON), P<0.05). Compared with HYP(CON), VO(2) at rest and during EX(45%) was lower in HYP(BR) (P<0.05), whilst %SpO(2) was higher (P<0.05). TOI(M) was ~4-5% higher in HYP(BR) than in HYP(CON) both at rest (P<0.05) and during EX(45%) and EX(max) (P<0.05). TOI(C) as well as the incidence of AMS symptoms were similar between HYP(CON) and HYP(BR) at any time. Hypoxia reduced time to exhaustion in EX(max) by 36% (P<0.05), but this ergolytic effect was partly negated by BR (+5%, P<0.05). Conclusion: Short-term dietary nitrate supplementation improves arterial and muscle oxygenation status, but not cerebral oxygenation status, during exercise in severe hypoxia. This is associated with improved exercise tolerance against the background of similar incidence of AMS. |
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Authors:
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Evi Masschelein; Ruud Van Thienen; Xu Wang; Ann Van Schepdael; Martine Thomis; Peter Hespel |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2012-7-5 |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: - ISSN: 1522-1601 ISO Abbreviation: - Publication Date: 2012 Jul |
Date Detail:
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Created Date: 2012-7-9 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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1KU Leuven. |
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