Effect of induced acute metabolic alkalosis on the V̇E/V̇CO2 response to exercise in healthy adults.

We tested the hypothesis that increasing the respiratory control systems' arterial PCO2 equilibrium point via induced acute metabolic alkalosis by ingestion of sodium bicarbonate (NaHCO3, 0.3 g/kg) would decrease the ventilatory equivalent for CO2 (V̇E/V̇CO2) at its lowest point ("nadir") during constant-load cycle exercise testing performed at 80 % of peak power output in 18 healthy young adults. Compared to the sodium chloride (4 g) control condition, ingestion of NaHCO3: increased arterialized venous pH, HCO3- and PCO2 at rest by 0.05 ± 0.01 units (mean ± SE), 6.4 ± 0.4 mEq/L and 4.3 ± 0.7 mmHg, respectively (all p < 0.0001); and decreased the V̇E/V̇CO2 nadir during exercise by 9.4 % (p < 0.0001) secondary to a 4.7 ± 1.8 L/min decrease in V̇E (p = 0.019). In conclusion, induced acute metabolic alkalosis by ingestion of NaHCO3 decreased the V̇E/V̇CO2 response to strenuous exercise in healthy adults.