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Multiple-day high-dose beetroot juice supplementation does not improve pulmonary or muscle deoxygenation kinetics of well-trained cyclists in normoxia and hypoxia
Nitric Oxide ( IF 3.9 ) Pub Date : 2021-04-05 , DOI: 10.1016/j.niox.2021.03.006
Torben Rokkedal-Lausch 1 , Jesper Franch 1 , Mathias K Poulsen 2 , Lars P Thomsen 2 , Eddie Weitzberg 3 , Ernest N Kamavuako 4 , Dan S Karbing 2 , Ryan G Larsen 1
Affiliation  

Dietary nitrate (NO3) supplementation via beetroot juice (BR) has been reported to lower oxygen cost (i.e., increased exercise efficiency) and speed up oxygen uptake (VO2) kinetics in untrained and moderately trained individuals, particularly during conditions of low oxygen availability (i.e., hypoxia). However, the effects of multiple-day, high dose (12.4 mmol NO3− per day) BR supplementation on exercise efficiency and VO2 kinetics during normoxia and hypoxia in well-trained individuals are not resolved. In a double-blinded, randomized crossover study, 12 well-trained cyclists (66.4 ± 5.3 ml min−1∙kg−1) completed three transitions from rest to moderate-intensity (~70% of gas exchange threshold) cycling in hypoxia and normoxia with supplementation of BR or nitrate-depleted BR as placebo. Continuous measures of VO2 and muscle (vastus lateralis) deoxygenation (ΔHHb, using near-infrared spectroscopy) were acquired during all transitions. Kinetics of VO2 and deoxygenation (ΔHHb) were modeled using mono-exponential functions. Our results showed that BR supplementation did not alter the primary time constant for VO2 or ΔHHb during the transition from rest to moderate-intensity cycling. While BR supplementation lowered the amplitude of the VO2 response (2.1%, p = 0.038), BR did not alter steady state VO2 derived from the fit (p = 0.258), raw VO2 data (p = 0.231), moderate intensity exercise efficiency (p = 0.333) nor steady state ΔHHb (p = 0.224). Altogether, these results demonstrate that multiple-day, high-dose BR supplementation does not alter exercise efficiency or oxygen uptake kinetics during normoxia and hypoxia in well-trained athletes.



中文翻译:

多日高剂量甜菜根汁补充剂在常氧和缺氧条件下不会改善训练有素的自行车手的肺或肌肉脱氧动力学

据报道,通过甜菜根汁 (BR) 补充膳食硝酸盐 (NO 3 - ) 可以降低氧气消耗(即提高运动效率)并加速未经训练和中等训练的个体的氧气摄取 (VO 2 ) 动力学,特别是在低氧条件下氧气可用性(即缺氧)。然而,在训练有素的个体中,多日、高剂量(每天 12.4 mmol NO 3−)补充 BR 对正常氧和缺氧期间的运动效率和 VO 2动力学的影响尚未解决。在一项双盲、随机交叉研究中,12 名训练有素的自行车手 (66.4 ± 5.3 ml min -1 ∙kg -1) 完成了从休息到中等强度(~70% 的气体交换阈值)循环的三个过渡,在缺氧和常氧条件下,补充 BR 或耗尽硝酸盐的 BR 作为安慰剂。VO 2和肌肉(外侧大肌)脱氧(ΔHHb,使用近红外光谱)的连续测量在所有转换过程中都被获得。VO 2和脱氧(ΔHHb)的动力学使用单指数函数建模。我们的结果表明,在从休息到中等强度循环的过渡期间,BR 补充剂不会改变 VO 2或 ΔHHb的主要时间常数。虽然补充 BR 降低了 VO 2响应的幅度(2.1%,p = 0.038),但 BR 并未改变稳态 VO 2源自拟合 (p = 0.258)、原始 VO 2数据 (p = 0.231)、中等强度运动效率 (p = 0.333) 或稳态 ΔHHb (p = 0.224)。总之,这些结果表明,在训练有素的运动员中,在常氧和缺氧期间,多日、高剂量的 BR 补充剂不会改变运动效率或摄氧动力学。

更新日期:2021-04-16
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