Effects of nitrate supplementation in trained and untrained muscle are modest with initial high plasma nitrite levels.
Nitrate (NO3-) supplementation resulting in higher plasma nitrite (NO2-) is reported to lower resting mean arterial blood pressure (MAP) and oxygen uptake (VO2) during submaximal exercise in non-athletic populations, whereas effects in general are absent in endurance-trained individuals. To test whether physiologic effects of NO3- supplementation depend on local muscular training status or cardiovascular fitness, male endurance-trained cyclists (CYC, n=9, VO2-max: 64±3 mL/min/kg; mean±SD) and recreational active subjects serving as a control group (CON, n=8, 46±3 mL/min/kg), acutely consumed nitrate-rich beetroot juice ([NO3-] ~9 mmol) (NIT) or placebo (PLA) with assessment of resting MAP and energy expenditure during moderate intensity (~50% VO2-max) and incremental leg cycling (LEG-ex) and arm-cranking exercise (ARM-ex). NIT increased (P<.001) resting plasma NO3- by ~1200% relative to PLA. Plasma NO2- increased ~25% (P<.01) with a significant change only in CYC. LEG-ex VO2(~2.60 L/min), ARM-ex VO2(~1.14 L/min), and resting MAP (~87 mm Hg) remained unchanged for CYC, and similarly for CON, no changes were observed for LEG-ex VO2(~2.03 L/min), ARM-ex VO2(~1.06 L/min), or resting MAP (~85 mm Hg). VO2-max was not affected by supplementation, but incremental test peak power was higher (P<.05) in LEG-ex for CYC in NIT relative to PLA (418±47 vs 407±46 W). In both CYC and CON, high initial baseline values and small increases in plasma NO2- after NIT may have lowered the effect of the intervention implying that muscular and cardiovascular training status is likely not the only factors that influence the physiologic effects of NO3- supplementation.
Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Copenhagen, Denmark.|Team Danmark (Danish elite sport organization), Copenhagen, Denmark.
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http://orcid.org/0000-0002-8277-6093
PM
Christensen
Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Copenhagen, Denmark.
N K
NK
Petersen
Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Copenhagen, Denmark.
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SN
Friis
Department of Physiology and Pharmacology, Swedish School of Sport and Health Sciences, Karolinska Institutet, Stockholm, Sweden.
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E
Weitzberg
Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Copenhagen, Denmark.
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L
Nybo
D000328:Adult; D056352:Athletes; D027461:Beta vulgaris; D001642:Bicycling / Q000502:physiology*; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D004734:Energy Metabolism; D000067030:Fruit and Vegetable Juices; D006801:Humans; D008297:Male; D009573:Nitrites / Q000008:administration & dosage* / Q000097:blood*; D010101:Oxygen Consumption; D064133:Sports Nutritional Physiological Phenomena; D055815:Young Adult
D009573:Nitrites
NO bioavailability; VO2-max; blood pressure; cycling economy