Affiliation:
1. Faculty of Health and Life Sciences University of Exeter Medical School Exeter UK
2. Molecular Medicine Branch, NIDDK National Institutes of Health Bethesda Maryland USA
3. School of Sport, Exercise and Health Sciences Loughborough University Loughborough UK
4. Clinical Mass Spectrometry Core, NIDDK National Institutes of Health Bethesda Maryland USA
Abstract
AbstractAimDietary nitrate (NO3−) supplementation increases nitric oxide bioavailability and can enhance exercise performance. We investigated the distribution and metabolic fate of ingested NO3− at rest and during exercise with a focus on skeletal muscle.MethodsIn a randomized, crossover study, 10 healthy volunteers consumed 12.8 mmol 15N‐labeled potassium nitrate (K15NO3; NIT) or potassium chloride placebo (PLA). Muscle biopsies were taken at baseline, at 1‐ and 3‐h post‐supplement ingestion, and immediately following the completion of 60 maximal intermittent contractions of the knee extensors. Muscle, plasma, saliva, and urine samples were analyzed using chemiluminescence to determine absolute [NO3−] and [NO2−], and by mass spectrometry to determine the proportion of NO3− and NO2− that was 15N‐labeled.ResultsNeither muscle [NO3−] nor [NO2−] were altered by PLA. Following NIT, muscle [NO3−] (but not [NO2−]) was elevated at 1‐h (from ~35 to 147 nmol/g, p < 0.001) and 3‐h, with almost all of the increase being 15N‐labeled. There was a significant reduction in 15N‐labeled muscle [NO3−] from pre‐ to post‐exercise. Relative to PLA, mean muscle torque production was ~7% greater during the first 18 contractions following NIT. This improvement in torque was correlated with the pre‐exercise 15N‐labeled muscle [NO3−] and the magnitude of decline in 15N‐labeled muscle [NO3−] during exercise (r = 0.66 and r = 0.62, respectively; p < 0.01).ConclusionThis study shows, for the first time, that skeletal muscle rapidly takes up dietary NO3−, the elevated muscle [NO3−] following NO3− ingestion declines during exercise, and muscle NO3− dynamics are associated with enhanced torque production during maximal intermittent muscle contractions.
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10 articles.
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