Blood lactate changes during exercise at high altitude.

Blood lactate concentrations were measured in 18 normal subjects at the end of an exercise test designed to maintain heart rate at 85% of maximum for 15 minutes. Blood lactate concentrations were reduced at high altitude (4846 m) and correlated positively with basal pH and negatively with basal Pa,O2 levels. Blood lactate concentrations tended to be lower in those subjects on acetazolamide but were not correlated with the severity of acute mountain sickness or with the workload of the exercise test. We conclude that the pH changes are probably the most significant factor in reducing lactate concentrations.