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J Appl Physiol (1985). 2014 Dec 15;117(12):1460-70. doi: 10.1152/japplphysiol.00096.2014. Epub 2014 Oct 9.

Dietary nitrate accelerates postexercise muscle metabolic recovery and O2 delivery in hypoxia.

Author information

1
College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom; a.vanhatalo@exeter.ac.uk.
2
College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom;
3
University of Exeter Medical School, Exeter, United Kingdom, University of Exeter, Exeter, United Kingdom; and.
4
NIHR Exeter Clinical Research Facility, University of Exeter Medical School, St. Luke's Campus, University of Exeter, Exeter, United Kingdom.

Abstract

We tested the hypothesis that the time constants (τ) of postexercise T2* MRI signal intensity (an index of O2 delivery) and muscle [PCr] (an index of metabolic perturbation, measured by (31)P-MRS) in hypoxia would be accelerated after dietary nitrate (NO3 (-)) supplementation. In a double-blind crossover design, eight moderately trained subjects underwent 5 days of NO3 (-) (beetroot juice, BR; 8.2 mmol/day NO3 (-)) and placebo (PL; 0.003 mmol/day NO3 (-)) supplementation in four conditions: normoxic PL (N-PL), hypoxic PL (H-PL; 13% O2), normoxic NO3 (-) (N-BR), and hypoxic NO3 (-) (H-BR). The single-leg knee-extension protocol consisted of 10 min of steady-state exercise and 24 s of high-intensity exercise. The [PCr] recovery τ was greater in H-PL (30 ± 4 s) than H-BR (22 ± 4 s), N-PL (24 ± 4 s) and N-BR (22 ± 4 s) (P < 0.05) and the maximal rate of mitochondrial ATP resynthesis (Qmax) was lower in the H-PL (1.12 ± 0.16 mM/s) compared with H-BR (1.35 ± 0.26 mM/s), N-PL (1.47 ± 0.28 mM/s), and N-BR (1.40 ± 0.21 mM/s) (P < 0.05). The τ of postexercise T2* signal intensity was greater in H-PL (47 ± 14 s) than H-BR (32 ± 10 s), N-PL (38 ± 9 s), and N-BR (27 ± 6 s) (P < 0.05). The postexercise [PCr] and T2* recovery τ were correlated in hypoxia (r = 0.60; P < 0.05), but not in normoxia (r = 0.28; P > 0.05). These findings suggest that the NO3 (-)-NO2 (-)-NO pathway is a significant modulator of muscle energetics and O2 delivery during hypoxic exercise and subsequent recovery.

KEYWORDS:

hypoxia; nitric oxide; nitrite; phosphocreatine; skeletal muscle

PMID:
25301896
PMCID:
PMC4269683
DOI:
10.1152/japplphysiol.00096.2014
[Indexed for MEDLINE]
Free PMC Article

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