Metabolic acidosis of exercise in healthy males.

Abstract

Lactic acid (LA), pH, standard bicarbonate (SB), and base excess (BE) in arterialized capillary blood, respiratory quotient (R) and "excess CO2" were measured in submaximal and maximal work tests. Comparison of indices of exercise acidosis showed: High values of R and of excess CO2 were associated with high LA values, but the reverse was not always true. A lesser degree of metabolic acidosis after maximum work in older subjects appeared from the LA, pH, SB, BE, and excess CO2 data, but not from the R values. A lesser degree of metabolic acidosis after a training period (four subjects) was shown by LA, pH, SB, and BE but not by R and excess CO2. Changes of SB in blood underestimate, while changes of BE in blood overestimate the amounts of acid added to blood during exercise. These discrepancies can be explained from the behavior of the buffer systems of blood and tissues. Direct determination of LA in blood remains the most accurate and reliable index of the development of a metabolic acidosis during exercise.