Dietary nitrate supplementation enhances muscle contractile efficiency during knee-extensor exercise in humans

SJ Bailey, J Fulford, A Vanhatalo, PG Winyard, JR Blackwell, FJ DiMenna, DP Wilkerson, N Benjamin, AM Jones

Research output: Contribution to journalArticlepeer-review

Abstract

<jats:p>The purpose of this study was to elucidate the mechanistic bases for the reported reduction in the O<jats:sub>2</jats:sub>cost of exercise following short-term dietary nitrate (NO<jats:sub>3</jats:sub><jats:sup>−</jats:sup>) supplementation. In a randomized, double-blind, crossover study, seven men (aged 19–38 yr) consumed 500 ml/day of either nitrate-rich beetroot juice (BR, 5.1 mmol of NO<jats:sub>3</jats:sub><jats:sup>−</jats:sup>/day) or placebo (PL, with negligible nitrate content) for 6 consecutive days, and completed a series of low-intensity and high-intensity “step” exercise tests on the last 3 days for the determination of the muscle metabolic (using<jats:sup>31</jats:sup>P-MRS) and pulmonary oxygen uptake (V̇o<jats:sub>2</jats:sub>) responses to exercise. On days 4–6, BR resulted in a significant increase in plasma [nitrite] (mean ± SE, PL 231 ± 76 vs. BR 547 ± 55 nM; P &lt; 0.05). During low-intensity exercise, BR attenuated the reduction in muscle phosphocreatine concentration ([PCr]; PL 8.1 ± 1.2 vs. BR 5.2 ± 0.8 mM; P &lt; 0.05) and the increase in V̇o<jats:sub>2</jats:sub>(PL 484 ± 41 vs. BR 362 ± 30 ml/min; P &lt; 0.05). During high-intensity exercise, BR reduced the amplitudes of the [PCr] (PL 3.9 ± 1.1 vs. BR 1.6 ± 0.7 mM; P &lt; 0.05) and V̇o<jats:sub>2</jats:sub>(PL 209 ± 30 vs. BR 100 ± 26 ml/min; P &lt; 0.05) slow components and improved time to exhaustion (PL 586 ± 80 vs. BR 734 ± 109 s; P &lt; 0.01). The total ATP turnover rate was estimated to be less for both low-intensity (PL 296 ± 58 vs. BR 192 ± 38 μM/s; P &lt; 0.05) and high-intensity (PL 607 ± 65 vs. BR 436 ± 43 μM/s; P &lt; 0.05) exercise. Thus the reduced O<jats:sub>2</jats:sub>cost of exercise following dietary NO<jats:sub>3</jats:sub><jats:sup>−</jats:sup>supplementation appears to be due to a reduced ATP cost of muscle force production. The reduced muscle metabolic perturbation with NO<jats:sub>3</jats:sub><jats:sup>−</jats:sup>supplementation allowed high-intensity exercise to be tolerated for a greater period of time.</jats:p>
Original languageEnglish
Pages (from-to)135-148
Number of pages0
JournalJournal of Applied Physiology
Volume109
Issue number1
DOIs
Publication statusPublished - Jul 2010

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