Document Detail

Dietary nitrate improves muscle but not cerebral oxygenation status during exercise in hypoxia.
MedLine Citation:
PMID:  22773768     Owner:  NLM     Status:  MEDLINE    
Exercise tolerance is impaired in hypoxia, and it has recently been shown that dietary nitrate supplementation can reduce the oxygen (O(2)) 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 at simulated 5,000 m altitude. Fifteen young, healthy volunteers participated in three experimental sessions according to a crossover study design. From 6 days prior to each session, subjects received either beetroot (BR) juice delivering 0.07 mmol nitrate/kg body wt/day 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 at 45% of peak O(2) consumption (VO(2)peak; EX(45%)) and thereafter, performed a maximal incremental exercise test (EX(max)). Whole-body VO(2), arterial O(2) saturation (%SpO(2)) via pulsoximetry, and tissue oxygenation index of both muscle (TOI(M)) and cerebral (TOI(C)) tissue by near-infrared spectroscopy were measured. 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), whereas %SpO(2) was higher (P < 0.05). TOI(M) was ~4-5% higher in HYP(BR) than in HYP(CON) both at rest 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). 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 a similar incidence of AMS.
Evi Masschelein; Ruud Van Thienen; Xu Wang; Ann Van Schepdael; Martine Thomis; Peter Hespel
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Publication Detail:
Type:  Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't     Date:  2012-07-05
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  113     ISSN:  1522-1601     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2012 Sep 
Date Detail:
Created Date:  2012-09-03     Completed Date:  2013-07-08     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  736-45     Citation Subset:  IM    
Research Center for Exercise and Health, Department of Biomedical Kinesiology, KU Leuven, Leuven, Belgium.
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MeSH Terms
Anoxia / diet therapy,  metabolism*
Brain / drug effects,  metabolism*
Cross-Over Studies
Dietary Supplements
Exercise / physiology*
Exercise Tolerance / drug effects,  physiology
Muscle, Skeletal / drug effects,  metabolism*
Nitrates / administration & dosage*,  blood
Oxygen Consumption / drug effects,  physiology*
Pulmonary Gas Exchange / drug effects,  physiology
Single-Blind Method
Young Adult
Reg. No./Substance:

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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