Multiday acute sodium bicarbonate intake improves endurance capacity and reduces acidosis in men

BACKGROUND: The purpose was to investigate the effects of one dose of NaHCO(3) per day for five consecutive days on cycling time-to-exhaustion (T(lim)) at ‘Critical Power’ (CP) and acid–base parameters in endurance athletes. METHODS: Eight trained male cyclists and triathletes completed two exercise periods in a randomized, placebo-controlled, double-blind interventional crossover investigation. Before each period, CP was determined. Afterwards, participants completed five constant-load cycling trials at CP until volitional exhaustion on five consecutive days, either after a dose of NaHCO(3) (0.3 g·kg(-1) body mass) or placebo (0.045 g·kg(-1) body mass NaCl). RESULTS: Average T(lim) increased by 23.5% with NaHCO(3) supplementation as compared to placebo (826.5 ± 180.1 vs. 669.0 ± 167.2 s; P = 0.001). However, there was no time effect for T(lim) (P = 0.375). [HCO(3)(-)] showed a main effect for condition (NaHCO(3): 32.5 ± 2.2 mmol·l(-1); placebo: 26.2 ± 1.4 mmol·l(-1); P < 0.001) but not for time (P = 0.835). NaHCO(3) supplementation resulted in an expansion of plasma volume relative to placebo (P = 0.003). CONCLUSIONS: The increase in T(lim) was accompanied by an increase in [HCO(3)(-)], suggesting that acidosis might be a limiting factor for exercise at CP. Prolonged NaHCO(3) supplementation did not lead to a further increase in [HCO(3)(-)] due to the concurrent elevation in plasma volume. This may explain why T(lim) remained unaltered despite the prolonged NaHCO(3) supplementation period. Ingestion of one single NaHCO(3) dose per day before the competition during multiday competitions or tournaments might be a valuable strategy for performance enhancement. TRIAL REGISTRATION: Trial registration: ClinicalTrials.gov Identifier NCT01621074