The effect of sodium bicarbonate mini-tablets in a carbohydrate hydrogel on prolonged high-intensity cycling performance and metabolism in acute normobaric hypoxia

Hydrogen cation (H+) accumulation is exacerbated in hypoxia. Sodium bicarbonate (NaHCO3) ingestion can reduce fatigue associated with high-intensity exercise performance by counteracting H+ ion accumulation. The present study aimed to determine the effect of 0.3 g·kg− 1 NaHCO3 mini-tablets in a carbohydrate hydrogel on 40 km cycling time trial (TT) performance in trained male cyclists in acute hypoxia. Fourteen trained male cyclists completed a ramp test to determine VO2Peak. After, in a randomised, double-blinded, placebo-controlled crossover study, participants completed three 40 km cycling TTs (1 x familiarisation, 2 x experimental) in acute hypoxia (16.7 ± 0.2 FiO2). Each experimental TT followed 90 min after the ingestion of 0.3 g·kg− 1 BM NaHCO3 or an appearance-matched placebo. After NaHCO3 ingestion, 40 km cycling TT performance was improved by 1.2% in comparison to placebo (t = 3.84, p = 0.02, g = 0.19). Additionally, NaHCO3 ingestion raised blood pH (f = 48.47, p = < 0.001, pη2 = 0.79) and blood HCO3− (f = 64.13, p = < 0.001, pη2 = 0.84) pre-exercise and throughout the TT. Aggregated gastrointestinal symptoms (GIS) were minimal, and did not differ between conditions (NaHCO3, 110 AU; Placebo, 119 AU; z = 0.38, p = 0.71, r = 0.10). The present study suggests that 0.3 g·kg− 1 NaHCO3 can enhance 40 km cycling TT performance in acute hypoxia, likely a result of improved buffering capacity. Cyclists competing at altitude could consider the ingestion of this form of NaHCO3 to minimise the deleterious effects of acute hypoxia.