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Nitric Oxide. 2019 Jan 24;85:44-52. doi: 10.1016/j.niox.2019.01.011. [Epub ahead of print]

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

Author information

1
Sport Sciences, Department of Health Science and Technology, Aalborg University, DK-9220, Aalborg, Denmark. Electronic address: Torben@hst.aau.dk.
2
Sport Sciences, Department of Health Science and Technology, Aalborg University, DK-9220, Aalborg, Denmark.
3
Respiratory and Critical Care Group, Center for Model-based Medical Decision Support, Department of Health Science and Technology, Aalborg University, DK-9220, Aalborg, Denmark.
4
Department of Physiology and Pharmacology, Karolinska Institutet, 171 77, Stockholm, Sweden.
5
Center for Robotics Research, Department of Informatics, King's College London, London, United Kingdom; SMI, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.

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

PMID:
30685420
DOI:
10.1016/j.niox.2019.01.011

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