title: Multiday acute sodium bicarbonate intake improves endurance capacity and reduces acidosis in men.
abstract: BACKGROUND
  The purpose was to investigate the effects of one dose of NaHCO3 per day for five consecutive days on cycling time-to-exhaustion (Tlim) 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 NaHCO3 (0.3 g·kg-1 body mass) or placebo (0.045 g·kg-1 body mass NaCl).
  
  
  RESULTS
  Average Tlim increased by 23.5% with NaHCO3 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 Tlim (P = 0.375). [HCO3-] showed a main effect for condition (NaHCO3: 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). NaHCO3 supplementation resulted in an expansion of plasma volume relative to placebo (P = 0.003).
  
  
  CONCLUSIONS
  The increase in Tlim was accompanied by an increase in [HCO3-], suggesting that acidosis might be a limiting factor for exercise at CP. Prolonged NaHCO3 supplementation did not lead to a further increase in [HCO3-] due to the concurrent elevation in plasma volume. This may explain why Tlim remained unaltered despite the prolonged NaHCO3 supplementation period. Ingestion of one single NaHCO3 dose per day before the competition during multiday competitions or tournaments might be a valuable strategy for performance enhancement.
  
  
  BACKGROUND
  Trial registration: ClinicalTrials.gov Identifier NCT01621074.
authors.affiliation: Exercise Physiology, Institute of Human Movement Sciences, ETH Zurich, Zurich, Switzerland. marco.toigo@hest.ethz.ch.
authors.forename: Sandro Manuel
authors.initials: SM
authors.lastname: Mueller
authors.forename: Saskia Maria
authors.initials: SM
authors.lastname: Gehrig
authors.forename: Sebastian
authors.initials: S
authors.lastname: Frese
authors.forename: Carsten Alexander
authors.initials: CA
authors.lastname: Wagner
authors.forename: Urs
authors.initials: U
authors.lastname: Boutellier
authors.forename: Marco
authors.initials: M
authors.lastname: Toigo