Dietary nitrate accelerates postexercise muscle metabolic recovery and O2delivery in hypoxia

A Vanhatalo, AM Jones, JR Blackwell, PG Winyard, J Fulford

Research output: Contribution to journalArticlepeer-review

Abstract

<jats:p>We tested the hypothesis that the time constants (τ) of postexercise T2* MRI signal intensity (an index of O<jats:sub>2</jats:sub>delivery) and muscle [PCr] (an index of metabolic perturbation, measured by<jats:sup>31</jats:sup>P-MRS) in hypoxia would be accelerated after dietary nitrate (NO<jats:sub>3</jats:sub><jats:sup>−</jats:sup>) supplementation. In a double-blind crossover design, eight moderately trained subjects underwent 5 days of NO<jats:sub>3</jats:sub><jats:sup>−</jats:sup>(beetroot juice, BR; 8.2 mmol/day NO<jats:sub>3</jats:sub><jats:sup>−</jats:sup>) and placebo (PL; 0.003 mmol/day NO<jats:sub>3</jats:sub><jats:sup>−</jats:sup>) supplementation in four conditions: normoxic PL (N-PL), hypoxic PL (H-PL; 13% O<jats:sub>2</jats:sub>), normoxic NO<jats:sub>3</jats:sub><jats:sup>−</jats:sup>(N-BR), and hypoxic NO<jats:sub>3</jats:sub><jats:sup>−</jats:sup>(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 &lt; 0.05) and the maximal rate of mitochondrial ATP resynthesis (Q<jats:sub>max</jats:sub>) 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 &lt; 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 &lt; 0.05). The postexercise [PCr] and T2* recovery τ were correlated in hypoxia ( r = 0.60; P &lt; 0.05), but not in normoxia ( r = 0.28; P &gt; 0.05). These findings suggest that the NO<jats:sub>3</jats:sub><jats:sup>−</jats:sup>-NO<jats:sub>2</jats:sub><jats:sup>−</jats:sup>-NO pathway is a significant modulator of muscle energetics and O<jats:sub>2</jats:sub>delivery during hypoxic exercise and subsequent recovery.</jats:p>
Original languageEnglish
Pages (from-to)1460-1470
Number of pages0
JournalJournal of Applied Physiology
Volume117
Issue number12
DOIs
Publication statusPublished - 15 Dec 2014

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