Sodium bicarbonate supplementation improves severe-intensity intermittent exercise under moderate acute hypoxic conditions

Acute moderate hypoxic exposure can substantially impair exercise performance, which occurs with a concurrent exacerbated rise in hydrogen cation (H+) production. The purpose of this study was therefore, to alleviate this acidic stress through sodium bicarbonate (NaHCO3) supplementation and determine the corresponding effects on severe intensity intermittent exercise performance. Eleven recreationally active individuals participated in this randomised, double-blind, crossover study performed under acute normobaric hypoxic conditions (FiO2% = 14.5%). Pre-experimental trials involved the determination of time to attain peak bicarbonate anion concentrations ([HCO3-]) following NaHCO3 ingestion. The intermittent exercise tests involved repeated 60 s work in their severe intensity domain and 30 s recovery at 20 W to exhaustion. Participants ingested either 0.3 g·kg bm-1 of NaHCO3 or a matched placebo of 0.21 g·kg bm-1 of sodium chloride prior to exercise. Exercise tolerance (+110.9 ± 100.6 s; 95% CI: 43.3 to 178 s; g = 1.0) and work performed in the severe intensity domain (+5.8 ± 6.6 kJ; 95% CI: 1.3 to 9.9 kJ; g = 0.8) were enhanced with NaHCO3 supplementation. Furthermore, a larger post-exercise blood lactate concentration was reported in the experimental group (+4 ± 2.4 mmol·l-1; 95% CI: 2.2 to 5.9; g = 1.8), while blood [HCO3-] and pH remained elevated in the NaHCO3 condition throughout experimentation. In conclusion, this study reported a positive effect of NaHCO3 under acute moderate hypoxic conditions during intermittent exercise and therefore, may offer an ergogenic strategy to mitigate hypoxic induced declines in exercise performance.