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

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 (V˙O2), V˙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.

Nutritional Ergogenic Aids in Cycling: A Systematic Review

“…After the inclusion criteria were evaluated, 141 articles were excluded based on title and abstract screening, resulting in a total of 41 articles. Additionally, a total of five articles were excluded after full-text screening due to combining supplemental treatment with hypoxia [ 11 ], lacking a control group consuming a placebo [ 12 ], not measuring performance variables such as time or power output [ 13 ], and not meeting the inclusion requirements for study design, as they were not randomized studies [ 14 , 15 ]. Finally, 36 articles were selected for this systematic review ( Figure 1 ).…”

Limited Effects of Inorganic Nitrate Supplementation on Exercise Training Responses: A Systematic Review and Meta-analysis

“…Both outcomes produced similar results on the RoB analysis. Of the 9 included studies, 7 were considered to have a low risk of bias, with 2 having some concern due to the nature of their single-blinded supplement design [ 33 ] or lack of explicit mentioning of double-blinding [ 31 ] (Additional file 1 : Figure S1).…”

“…Theoretically, these individuals will have greater responses to training and to NO 3 − supplementation, but this was not the case. For example, the study with the highest improvement in VO 2peak following NO 3 − supplementation compared to control (∆ 5.5 vs. 3.0 ml/kg/min, respectively), was also the group with the highest baseline fitness (~ 60 mL/kg/min) [ 31 ], whereas the study group that experienced the largest difference in TTE following NO 3 − supplementation compared to control (∆ -2 vs. -95 s, respectively), had the second highest baseline fitness (~ 56 mL/kg/min) [ 33 ]. Further, the VO 2peak improvements were low in the clinical populations, averaging only 0.55 ml/kg/min across all conditions, although this may be due to the more moderate exercise intensity used in these studies compared to the healthy population studies which all employed high intensity or sprint interval training [ 51 ].…”