15 N-labeled dietary nitrate supplementation increases human skeletal muscle nitrate concentration and improves muscle torque production

Acta Physiol (Oxf). 2023 Mar;237(3):e13924. doi: 10.1111/apha.13924. Epub 2023 Jan 18.


Aim: Dietary 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.

Methods: In a randomized, crossover study, 10 healthy volunteers consumed 12.8 mmol 15 N-labeled potassium nitrate (K15 NO3 ; 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 15 N-labeled.

Results: Neither 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 15 N-labeled. There was a significant reduction in 15 N-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 15 N-labeled muscle [NO3 - ] and the magnitude of decline in 15 N-labeled muscle [NO3 - ] during exercise (r = 0.66 and r = 0.62, respectively; p < 0.01).

Conclusion: This 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.

Keywords: contraction; exercise; metabolism; nitric oxide; nitrite; performance.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Blood Pressure / physiology
  • Cross-Over Studies
  • Dietary Supplements
  • Double-Blind Method
  • Humans
  • Muscle, Skeletal / metabolism
  • Nitrates*
  • Nitric Oxide / metabolism
  • Nitrites*
  • Nitrogen Dioxide
  • Polyesters
  • Torque


  • Nitrates
  • Nitrites
  • Nitrogen Dioxide
  • Nitric Oxide
  • Polyesters