Abstract Title:

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

Abstract Source:

J Appl Physiol. 2010 May 13. Epub 2010 May 13. PMID: 20466802

Abstract Author(s):

Stephen J Bailey, Jonathan Fulford, Anni Vanhatalo, Paul G Winyard, Jamie R Blackwell, Fred J DiMenna, Daryl P Wilkerson, Nigel Benjamin, Andrew M Jones

Article Affiliation:

1Exeter University.

Abstract:

The purpose of this study was to elucidate the mechanistic bases for the reported reduction in the O(2) cost of exercise following short-term dietary nitrate (NO(3)(-)) supplementation. In a randomised, double-blind, crossover study, seven males (aged 19-38 yr) consumed 500 mL per day of either nitrate-rich beetroot juice (BR, 5.1 mmol of NO(3)(-.)day(-1)) or placebo (PL, with negligible nitrate content) for six consecutive days, and completed a series of low-intensity and high-intensity 'step' exercise tests on the last three days for the determination of the muscle metabolic (using (31)P-MRS) and pulmonary oxygen uptake (V(O2)) responses to exercise. On days 4-6, BR resulted in a significant increase in plasma [nitrite] (mean +/- SEM, PL: 231 +/- 76 vs. BR: 547 +/- 55 nM; P<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<0.05) and the increase in V(O2) (PL: 484 +/- 41 vs. BR: 362 +/- 30 ml(.)min(-1); P<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<0.05) and V(O2) (PL: 209 +/- 30 vs. BR: 100 +/- 26 ml(.)min(-1); P<0.05) slow components and improved time-to-exhaustion (PL: 586 +/- 80 vs. BR: 734 +/- 109 s; P<0.01). The total ATP turnover rate was estimated to be less for both low-intensity (PL: 296 +/- 58 vs. BR: 192 +/- 38 muM(.)s(-1); P<0.05) and high-intensity (PL: 607 +/- 65 vs. BR: 436 +/- 43 muM(.)s(-1); P<0.05) exercise. Thus, the reduced O(2) cost of exercise following dietary NO(3)(-) supplementation appears to be due to a reduced ATP cost of muscle force production. The reduced muscle metabolic perturbation with NO(3)(-) supplementation allowed high-intensity exercise to be tolerated for a greater period of time.

Study Type : Human Study

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