Dietary Nitrate Supplementation Is Not Helpful for Endurance Performance at Simulated Altitude Even When Combined With Intermittent Normobaric Hypoxic Training.

Ana Sousa,Grégoire P Millet,Jaime Milheiro,João L Viana,Vítor M Reis

doi:10.3389/fphys.2022.839996

Abstract

IntroductionTraining intensity and nutrition may influence adaptations to training performed in hypoxia and consequently performance outcomes at altitude. This study investigates if performance at simulated altitude is improved to a larger extent when high-intensity interval training is performed in normobaric hypoxia and if this is potentiated when combined with chronic dietary nitrate (NO3−) supplementation.MethodsThirty endurance-trained male participants were allocated to one of three groups: hypoxia (13% FiO2) + NO3−; hypoxia + placebo; and normoxia (20.9% FiO2) + placebo. All performed 12 cycling sessions (eight sessions of 2*6 × 1 min at severe intensity with 1 min recovery and four sessions of 4*6*10 s all-out with 20 s recovery) during a 4-week period (three sessions/week) with supplementation administered 3–2.5 h before each session. An incremental exhaustion test, a severe intensity exercise bout to exhaustion (Tlim) and a 3 min all-out test (3AOT) in hypoxia (FiO2 = 13%) with pulmonary oxygen uptake (O2), O2 kinetics, and changes in vastus lateralis local O2 saturation (SmO2) measured were completed by each participant before and after training.ResultsIn all tests, performance improved to the same extent in hypoxia and normoxia, except for SmO2 after Tlim (p = 0.04, d = 0.82) and 3AOT (p = 0.03, d = 1.43) which were lower in the two hypoxic groups compared with the normoxic one. Dietary NO3− supplementation did not bring any additional benefits.ConclusionPerformance at simulated altitude was not improved to a larger extent when high-intensity interval training was undertaken in normobaric hypoxic conditions, when compared with normoxic training. Additionally, dietary NO3− supplementation was ineffective in further enhancing endurance performance at simulated altitude.

Highlights

Training intensity and nutrition may influence adaptations to training performed in hypoxia and performance outcomes at altitude
Except for VT1-W which was higher in hypoxia compared to normoxia (p = 0.03, d = 0.62), no other differences were found, inclusively between chronic dietary NO3− supplementation vs. placebo condition
Some improvements in anaerobic performance have been reported (Daniels and Oldridge, 1970; Gore et al, 1998; Friedmann et al, 2005; studies “uncontrolled”), it is extensively reported that no additional benefit on the aerobic performance of endurance athletes occurs when conducting interval training in a hypoxic environment, compared with the same training performed in normoxia

Summary

Introduction

Training intensity and nutrition may influence adaptations to training performed in hypoxia and performance outcomes at altitude. This study investigates if performance at simulated altitude is improved to a larger extent when highintensity interval training is performed in normobaric hypoxia and if this is potentiated when combined with chronic dietary nitrate (NO3−) supplementation. By adding the stress of hypoxia during both aerobic or anaerobic interval training, performance at sea level in endurance athletes may not increase any more than perform the same training at sea level (Faiss et al, 2013a). Benefits on sea-level performance, if training stimulus would be increased (allowing higher recruitment of fast twitch fibers), are still ambiguous (Lundby et al, 2012), and presently unknown when preparing athletes for altitude performance

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