SODIUM-BICARBONATE INGESTION DOES NOT IMPROVE PERFORMANCE IN WOMEN CYCLISTS

We hypothesized that oral ingestion of sodium bicarbonate (NaHCO3) wou ld improve performance in seven competitive female cyclists VO2 = 51.6 +/- 4.8 ml.kg(-1).min(-1) at moderate altitude (2800 m). Two hours be fore exercise subjects ingested either NaHCO3 (300 mg.kg(-1)) or NaCl (207 mg.kg(-1)), both containing equimolar amounts of sodium. The exer cise protocol consisted of repeated 1-min intervals at 95% VO2max (277 +/- 38 W) followed by 1 min of recovery at 60 W until exhaustion. Con tinuous cardiopulmonary physiologic variables and arterialized venous blood gases were measured. Maximum interval ventilation, heart rate, a nd VO2 did not differ between the two interventions, but pH was signif icantly higher before and throughout the NaHCO3 trial. pH values for N aHCO3 vs NaCl trials were 7.47 +/- 0.04 vs 7.40 +/- 0.03 prior to exer cise 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 diffe rent from NaCl (8.4 +/- 0.9). The failure of bicarbonate to enhance pe rformance at moderate altitude may be attributed to our controlling fo r the amount of sodium ingested. The intravascular volume expansion wi th NaHCO3 rather than the increase in blood buffer capacity may underl ie the previously reported benefit of orally ingested bicarbonate in e xercise performance.