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Effects of dietary nitrate supplementation on physiological responses, cognitive function, and exercise performance at moderate and very-high simulated altitude

Lookup NU author(s): Dr Oliver ShannonORCiD, Dr Long Xie, Professor Bloss Stephan, Dr Mario Siervo

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

© 2017 Shannon, Duckworth, Barlow, Deighton, Matu, Williams, Woods, Xie, Stephan, Siervo and O'Hara. Purpose: Nitric oxide (NO) bioavailability is reduced during acute altitude exposure, contributing toward the decline in physiological and cognitive function in this environment. This study evaluated the effects of nitrate (NO3-) supplementation on NO bioavailability, physiological and cognitive function, and exercise performance at moderate and very-high simulated altitude. Methods:Ten males (mean (SD): V˙O2max: 60.9 (10.1) ml·kg-1·min-1) rested and performed exercise twice at moderate (~14.0% O2; ~3,000 m) and twice at very-high (~11.7% O2; ~4,300 m) simulated altitude. Participants ingested either 140 ml concentrated NO3--rich (BRJ; ~12.5 mmol NO3-) or NO3--deplete (PLA; 0.01 mmol NO3-) beetroot juice 2 h before each trial. Participants rested for 45 min in normobaric hypoxia prior to completing an exercise task. Exercise comprised a 45 min walk at 30% V˙O2max and a 3 km time-trial (TT), both conducted on a treadmill at a 10% gradient whilst carrying a 10 kg backpack to simulate altitude hiking. Plasma nitrite concentration ([NO2-]), peripheral oxygen saturation (SpO2), pulmonary oxygen uptake (V˙O2), muscle and cerebral oxygenation, and cognitive function were measured throughout. Results: Pre-exercise plasma [NO2-] was significantly elevated in BRJ compared with PLA (p = 0.001). Pulmonary V˙O2 was reduced (p = 0.020), and SpO2 was elevated (p = 0.005) during steady-state exercise in BRJ compared with PLA, with similar effects at both altitudes. BRJ supplementation enhanced 3 km TT performance relative to PLA by 3.8% [1,653.9 (261.3) vs. 1718.7 (213.0) s] and 4.2% [1,809.8 (262.0) vs. 1,889.1 (203.9) s] at 3,000 and 4,300 m, respectively (p = 0.019). Oxygenation of the gastrocnemius was elevated during the TT consequent to BRJ (p = 0.011). The number of false alarms during the Rapid Visual Information Processing Task tended to be lower with BRJ compared with PLA prior to altitude exposure (p = 0.056). Performance in all other cognitive tasks did not differ significantly between BRJ and PLA at any measurement point (p ≥ 0.141). Conclusion: This study suggests that BRJ improves physiological function and exercise performance, but not cognitive function, at simulated moderate and very-high altitude.

Publication metadata

Author(s): Shannon OM, Duckworth L, Barlow MJ, Deighton K, Matu J, Williams EL, Woods D, Xie L, Stephan BCM, Siervo M, O'Hara JP

Publication type: Article

Publication status: Published

Journal: Frontiers in Physiology

Year: 2017

Volume: 8

Online publication date: 09/06/2017

Acceptance date: 29/05/2017

Date deposited: 05/07/2017

ISSN (electronic): 1664-042X

Publisher: Frontiers Media S.A.

URL: https://doi.org/10.3389/fphys.2017.00401

DOI: 10.3389/fphys.2017.00401

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