Chronic high-dose beetroot juice supplementation improves time trial performance of well-trained cyclists in normoxia and hypoxia

Nitric Oxide. 2019 Apr 1;85:44-52. doi: 10.1016/j.niox.2019.01.011. Epub 2019 Jan 24.

Abstract

Dietary nitrate (NO3-) supplementation via beetroot juice (BR) is known to improve endurance performance in untrained and moderately trained individuals. However, conflicting results exist in well-trained individuals. Evidence suggests that the effects of NO3- are augmented during conditions of reduced oxygen availability (e.g., hypoxia), thereby increasing the probability of performance improvements for well-trained athletes in hypoxia vs. normoxia. This randomized, double-blinded, counterbalanced-crossover study examined the effects of 7 days of BR supplementation with 12.4 mmol NO3- per day on 10-km cycling time trial (TT) performance in 12 well-trained cyclists in normoxia (N) and normobaric hypoxia (H). Linear mixed models for repeated measures revealed increases in plasma NO3- and NO2- after supplementation with BR (both p < 0.001). Further, TT performance increased with BR supplementation (∼1.6%, p < 0.05), with no difference between normoxia and hypoxia (p = 0.92). For respiratory variables there were significant effects of supplementation on VO2 (p < 0.05) and VE (p < 0.05) such that average VO2 and VE during the TT increased with BR, with no difference between normoxia and hypoxia (p ≥ 0.86). We found no effect of supplementation on heart rate, oxygen saturation or muscle oxygenation during the TT. Our results provide new evidence that chronic high-dose NO3- supplementation improves cycling performance of well-trained cyclists in both normoxia and hypoxia.

Keywords: Cycling performance; Endurance exercise; Hypoxia; Nitrate; Nitrite.

Publication types

  • Clinical Trial

MeSH terms

  • Adult
  • Beta vulgaris / chemistry*
  • Cross-Over Studies
  • Dietary Supplements*
  • Dose-Response Relationship, Drug
  • Fruit and Vegetable Juices*
  • Humans
  • Hypoxia / metabolism*
  • Male
  • Oxygen / metabolism*
  • Oxygen Consumption
  • Time Factors
  • Young Adult

Substances

  • Oxygen