To determine the factors responsible for changes in [H+] during and after sprint exercise in the racing greyhound, Stewart's quantitative acid-base analysis was applied to arterial blood plasma samples taken at rest, at 8-s intervals during exercise, and at various intervals up to 30 min after a 402-m spring (approximately 30 s) on the track. [Na+], [K+], [Cl-], [total Ca], [lactate], [albumin], [Pi], PCO2, and pH were measured, and the [H+] was calculated from Stewart's equations. This short sprint caused all measured variables to change significantly. Maximal changes were strong ion difference decreased from 36.7 meq/l at rest to 16.1 meq/l; [albumin] increased from 3.1 g/dl at rest to 3.7 g/dl; PCO2, after decreasing from 39.6 Torr at rest to 27.9 Torr immediately prerace, increased during exercise to 42.8 Torr and then again decreased to near 20 Torr during most of recovery; and [H+] rose from 36.6 neq/l at rest to a peak of 76.6 neq/l. The [H+] calculated using Stewart's analysis was not significantly different from that directly measured. In addition to the increase in lactate and the change in PCO2, changes in [albumin], [Na+], and [Cl-] also influenced [H+] during and after sprint exercise in the running greyhound.
In defense of the Stewart approach to acid–base analysis
