Sodium bicarbonate ingestion does not improve performance in women cyclists

We hypothesized that oral ingestion of sodium bicarbonate (NaHCO3) would improve performance in seven competitive female cyclists VO2 = 51.6 +/- 4.8 ml.kg-1.min-1 at moderate altitude (2800 m). Two hours before exercise subjects ingested either NaHCO3 (300 mg.kg-1) or NaCl (207 mg.kg-1), both containing equimolar amounts of sodium. The exercise protocol consisted of repeated 1-min intervals at 95% VO2max (277 +/- 38 W) followed by 1 min of recovery at 60 W until exhaustion. Continuous cardiopulmonary physiologic variables and arterialized venous blood gases were measured. Maximum interval ventilation, heart rate, and VO2 did not differ between the two interventions, but pH was significantly higher before and throughout the NaHCO3 trial. pH values for NaHCO3 vs NaCl trials were 7.47 +/- 0.04 vs 7.40 +/- 0.03 prior to exercise and 7.32 +/- 0.08 vs 7.23 +/- 0.04 post-exercise (P < 0.01). The number of intervals completed with NaHCO3 (10.0 +/- 0.9) was not different from NaCl (8.4 +/- 0.9). The failure of bicarbonate to enhance performance at moderate altitude may be attributed to our controlling for the amount of sodium ingested. The intravascular volume expansion with NaHCO3 rather than the increase in blood buffer capacity may underlie the previously reported benefit of orally ingested bicarbonate in exercise performance.