Acidosis is a major factor that determines the upper limit of exercise endurance. We have previously shown that
anions usually associated with intermediary metabolism are elevated in
critically ill patients with
metabolic acidosis and contribute significantly to
acidosis generation. This study was to determine whether volunteers with normal metabolism would exhibit similar elevations in
anions associated with intermediate metabolism when exposed to a short-term physiological stress leading to a brief
lactic acidosis. Physiological stress was induced on five healthy male subjects by means of a ramped exercise protocol. Blood was obtained immediately prior to and post-exercise, plasma ultrafiltrate was prepared and analysed immediately both by
enzyme assay and liquid chromatography coupled to electrospray-mass spectrometry (LC/ESI-MS).
Metabolic acidosis concomitant with a significant increase in blood
lactate occurred in each subject, but in addition,
anions normally associated with intermediate metabolism were significantly elevated after exercise. The contribution of these
anions to generating an
acidosis, and thus potentially limiting the extent of exercise, has never been acknowledged.