Six healthy male subjects performed three exercise tests in which the power output was increased by 100 kpm/min each minute until exhaustion. The studies were carried out after
oral administration of CaCO3 (control), NH4Cl (
metabolic acidosis), and NaHCO3 (metabolic
alkalosis). Ventilation (VE), O2 intake (VO2), and CO2 output (VCO2) were monitored continuously. Arterialized-venous blood samples were drawn at specific times and analyzed for pH, PCO2, and
lactate concentration. Resting pH (mean +/- SE) was lowest in
acidosis (7.29 +/- 0.01) and highest in
alkalosis (7.46 +/- 0.02). A lower peak power output (kpm/min) was achieved in
acidosis (1,717 +/- 95) compared with control (1,867 +/- 120)
alkalosis (1,867 +/- 125). Submaximal VO2 and VCO2 were similar, but peak VO2 and VCO2 were lower in
acidosis. Plasma
lactate concentration was lower at rest and during exercise in
acidosis. Although
lactate accumulation was reduced in
acidosis, increases in hydrogen ion concentration were similar in the three conditions. We conclude that
acid-base changes influence the maximum power output that may be sustained in incremental dynamic exercise and modify plasma
lactate appearance, but have little effect on
hydrogen ion appearance in plasma.