title: [Physiological significance and interpretation of plasma lactate concentration and pH in clinical exercise testing].
abstract: According to a widely accepted model, based on the theory of the anaerobic threshold (AT), the increase in plasma lactate concentration which develops after the first ventilatory threshold (VT1, considered as an AT) is due to compensation for insufficient aerobic metabolism by anaerobic glycolysis, with accumulation of lactic acid resulting in a decrease in pH. Bicarbonate is the main buffer of protons (>90%) producing non-metabolic CO2 in muscle and thus increasing the CO2 flux to the lungs. This phenomenon, along with the low pH, triggers hyperventilation. Because of this model, great importance has been placed on plasma lactate and pH. We argue that this importance is excessive and these variables should be used with caution in the interpretation of clinical exercise testing, because the model based on AT is not valid: there is no aerobic failure above VT1 and, thus, there is no evidence of an AT; the increase in plasma lactate does not reflect anaerobiosis but is the marker of the increase in the error signal needed for the stimulation of mitochondrial respiration; bicarbonate is not the main buffer during exercise (these are proteins and phosphocreatine breakdown in the muscle; hemoglobin in the blood); non-metabolic CO2 is not produced in the muscle but in the lung because of the low pH and hyperventilation (the control of which remains unknown); and the flux of CO2 to the lung does not increase at faster rate after than before VT1.
authors.affiliation: Département de kinésiologie, université de Montréal, CP 6128, centre-ville, Montréal, QC, H3C 3J7, Canada. Electronic address: fperonnet@gmail.com.
authors.forename: F
authors.initials: F
authors.lastname: Péronnet
authors.affiliation: Faculté de médecine, université Joseph-Fourrier, domaine de La-Merci, avenue des Maquis-de-Grésivaudan, 38706 La Tronche cedex, France; Department of Kinesiology and Physical Education, McGill University, Montréal, Canada.
authors.forename: B
authors.initials: B
authors.lastname: Aguilaniu
mesh_terms: D000332:Aerobiosis / Q000502:physiology; D015308:Anaerobic Threshold; D001774:Blood Chemical Analysis; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006985:Hyperventilation / Q000097:blood; D019344:Lactic Acid / Q000097:blood*; D008962:Models, Theoretical; D005082:Physical Exertion / Q000502:physiology
chemical_list: D019344:Lactic Acid
keywords: Anaerobic; Anaérobie; Exercice; Exercise; Lactate; Seuil ventilatoire; Ventilatory threshold; pH