Sport and Health Sciences, College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom; and.
University of Exeter Medical School, St. Luke's Campus, University of Exeter, Heavitree Road, Exeter, United Kingdom.
Am J Physiol Regul Integr Comp Physiol. 2014 Oct 1;307(7):R920-30. doi: 10.1152/ajpregu.00068.2014. Epub 2014 Jul 9.
We investigated the effects of dietary nitrate (NO3 (-)) supplementation on the concentration of plasma nitrite ([NO2 (-)]), oxygen uptake (V̇o2) kinetics, and exercise tolerance in normoxia (N) and hypoxia (H). In a double-blind, crossover study, 12 healthy subjects completed cycle exercise tests, twice in N (20.9% O2) and twice in H (13.1% O2). Subjects ingested either 140 ml/day of NO3 (-)-rich beetroot juice (8.4 mmol NO3; BR) or NO3 (-)-depleted beetroot juice (PL) for 3 days prior to moderate-intensity and severe-intensity exercise tests in H and N. Preexercise plasma [NO2 (-)] was significantly elevated in H-BR and N-BR compared with H-PL (P < 0.01) and N-PL (P < 0.01). The rate of decline in plasma [NO2 (-)] was greater during severe-intensity exercise in H-BR [-30 ± 22 nM/min, 95% confidence interval (CI); -44, -16] compared with H-PL (-7 ± 10 nM/min, 95% CI; -13, -1; P < 0.01) and in N-BR (-26 ± 19 nM/min, 95% CI; -38, -14) compared with N-PL (-1 ± 6 nM/min, 95% CI; -5, 2; P < 0.01). During moderate-intensity exercise, steady-state pulmonary V̇o2 was lower in H-BR (1.91 ± 0.28 l/min, 95% CI; 1.77, 2.13) compared with H-PL (2.05 ± 0.25 l/min, 95% CI; 1.93, 2.26; P = 0.02), and V̇o2 kinetics was faster in H-BR (τ: 24 ± 13 s, 95% CI; 15, 32) compared with H-PL (31 ± 11 s, 95% CI; 23, 38; P = 0.04). NO3 (-) supplementation had no significant effect on V̇o2 kinetics during severe-intensity exercise in hypoxia, or during moderate-intensity or severe-intensity exercise in normoxia. Tolerance to severe-intensity exercise was improved by NO3 (-) in hypoxia (H-PL: 197 ± 28; 95% CI; 173, 220 vs. H-BR: 214 ± 43 s, 95% CI; 177, 249; P = 0.04) but not normoxia. The metabolism of NO2 (-) during exercise is altered by NO3 (-) supplementation, exercise, and to a lesser extent, hypoxia. In hypoxia, NO3 (-) supplementation enhances V̇o2 kinetics during moderate-intensity exercise and improves severe-intensity exercise tolerance. These findings may have important implications for individuals exercising at altitude.
我们研究了膳食硝酸盐（NO3 (-)）补充对血浆中亚硝酸盐（[NO2 (-)]）浓度、摄氧量（V̇o2）动力学和在常氧（N）和低氧（H）条件下运动耐量的影响。在一项双盲、交叉研究中，12 名健康受试者在 H（20.9% O2）和 H（13.1% O2）中进行了两次中度强度和两次剧烈强度的自行车运动测试，在此之前，他们分别服用了富含硝酸盐的甜菜根汁（8.4 mmol NO3；BR）或硝酸盐耗尽的甜菜根汁（PL），每天 140 毫升，持续 3 天。与 H-PL（P < 0.01）和 N-PL（P < 0.01）相比，H-BR 和 N-BR 运动前的血浆[NO2 (-)]水平显著升高。与 H-PL（-7 ± 10 nM/min，95%置信区间（CI）；-13，-1；P < 0.01）和 N-BR（-26 ± 19 nM/min，95% CI；-38，-14）相比，H-BR 进行剧烈运动时血浆[NO2 (-)]下降速度更快[-30 ± 22 nM/min，95% CI；-44，-16；P < 0.01]。在中度强度运动期间，与 H-PL（2.05 ± 0.25 l/min，95% CI；1.93，2.26）相比，H-BR（1.91 ± 0.28 l/min，95% CI；1.77，2.13）的稳态肺 V̇o2 更低，并且 H-BR 的 V̇o2 动力学更快（τ：24 ± 13 s，95% CI；15，32）与 H-PL（31 ± 11 s，95% CI；23，38；P = 0.04）。在 H 中的剧烈运动期间，NO3 (-) 补充对 V̇o2 动力学没有显著影响，或者在 N 中的中度或剧烈运动期间也没有显著影响。在 H 中，NO3 (-) 补充可提高剧烈运动的耐受性（H-PL：197 ± 28；95% CI；173，220 vs. H-BR：214 ± 43 s，95% CI；177，249；P = 0.04），但在 N 中则没有。NO2 (-) 在运动期间的代谢受 NO3 (-) 补充、运动以及在较小程度上受低氧的影响。在低氧条件下，NO3 (-) 补充可增强中度强度运动期间的 V̇o2 动力学，并提高剧烈运动的耐受力。这些发现可能对在高海拔地区运动的个体具有重要意义。
