title: Dietary nitrate supplementation enhances high-intensity running performance in moderate normobaric hypoxia, independent of aerobic fitness.
abstract: Nitrate-rich beetroot juice (BRJ) increases plasma nitrite concentrations, lowers the oxygen cost (V⋅O2) of steady-state exercise and improves exercise performance in sedentary and moderately-trained, but rarely in well-trained individuals exercising at sea-level. BRJ supplementation may be more effective in a hypoxic environment, where the reduction of nitrite into nitric oxide (NO) is potentiated, such that well-trained and less well-trained individuals may derive a similar ergogenic effect. We conducted a randomised, counterbalanced, double-blind placebo controlled trial to determine the effects of BRJ on treadmill running performance in moderate normobaric hypoxia (equivalent to 2500 m altitude) in participants with a range of aerobic fitness levels. Twelve healthy males (V⋅O2max ranging from 47.1 to 76.8 ml kg(-1) min(-1)) ingested 138 ml concentrated BRJ (∼15.2 mmol nitrate) or a nitrate-deplete placebo (PLA) (∼0.2 mmol nitrate). Three hours later, participants completed steady-state moderate intensity running, and a 1500 m time-trial (TT) in a normobaric hypoxic chamber (FIO2 ∼ 15%). Plasma nitrite concentration was significantly greater following BRJ versus PLA 1 h post supplementation, and remained higher in BRJ throughout the testing session (p < 0.01). Average V⋅O2 was significantly lower (BRJ: 18.4 ± 2.0, PLA: 20.4 ± 12.6 ml kg(-1) min(-1); p = 0.002), whilst arterial oxygen saturation (SpO2) was significantly greater (BRJ: 88.4 ± 2.7, PLA: 86.5 ± 3.3%; p < 0.001) following BRJ. BRJ improved TT performance in all 12 participants by an average of 3.2% (BRJ: 331.1 ± 45.3 vs. PL: 341.9 ± 46.1 s; p < 0.001). There was no apparent relationship between aerobic fitness and the improvement in performance following BRJ (r(2) = 0.05, p > 0.05). These findings suggests that a high nitrate dose in the form of a BRJ supplement may improve running performance in individuals with a range of aerobic fitness levels conducting moderate and high-intensity exercise in a normobaric hypoxic environment.
authors.affiliation: Institute for Sport, Physical Activity, and Leisure, Leeds Beckett University, Leeds, LS63QS, United Kingdom. Electronic address: O.Shannon@LeedsBeckett.ac.uk.
authors.forename: Oliver Michael
authors.initials: OM
authors.lastname: Shannon
authors.affiliation: Institute for Sport, Physical Activity, and Leisure, Leeds Beckett University, Leeds, LS63QS, United Kingdom.
authors.forename: Lauren
authors.initials: L
authors.lastname: Duckworth
authors.affiliation: Institute for Sport, Physical Activity, and Leisure, Leeds Beckett University, Leeds, LS63QS, United Kingdom.
authors.forename: Matthew John
authors.initials: MJ
authors.lastname: Barlow
authors.affiliation: Institute for Sport, Physical Activity, and Leisure, Leeds Beckett University, Leeds, LS63QS, United Kingdom; Defence Medical Services, Royal Centre for Defence Medicine, Birmingham, B152TH, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Woods
authors.affiliation: Department of Applied Sciences, Northumbria University, Newcastle upon Tyne, NE18ST, United Kingdom.
authors.forename: Jose
authors.initials: J
authors.lastname: Lara
authors.affiliation: Institute for Aging and Health, University of Newcastle, Newcastle upon Tyne, NE45PL, United Kingdom.
authors.forename: Mario
authors.initials: M
authors.lastname: Siervo
authors.affiliation: Institute for Sport, Physical Activity, and Leisure, Leeds Beckett University, Leeds, LS63QS, United Kingdom.
authors.forename: John Paul
authors.initials: JP
authors.lastname: O'Hara
mesh_terms: D000328:Adult; D062186:Arterial Pressure; D054874:Athletic Performance; D027461:Beta vulgaris; D019587:Dietary Supplements; D004311:Double-Blind Method; D000067030:Fruit and Vegetable Juices; D006801:Humans; D008297:Male; D009566:Nitrates / Q000008:administration & dosage* / Q000097:blood; D009573:Nitrites / Q000097:blood; D010100:Oxygen / Q000378:metabolism; D010809:Physical Fitness; D011897:Random Allocation; D012420:Running
chemical_list: D009566:Nitrates; D009573:Nitrites; D010100:Oxygen
keywords: Exercise performance; Hypoxia; Nitrate; Nitric oxide