title: Respiratory compensation and blood pH regulation during variable intensity exercise in trained versus untrained subjects.
abstract: To determine whether endurance-trained cyclists (T; n = 10) have a superior blood-respiratory buffering for metabolic acidosis relative to untrained subjects (UT; n = 10) during variable intensity exercise (VAR). On three occasions, T and UT pedaled for 24 min alternating high- and low-intensities as percentage of their second ventilatory threshold (VT2): VAR(LOW) 87.5-37.5% VT2, VAR(MODERATE) 125-25% VT2, and VAR(HIGH) 162.5-12.5% VT2 to complete the same amount of work. Before and just after each VAR trial, maximal cycling power (P(MAX)) was assessed. For each trial, the respiratory compensation for exercise acidosis (ventilatory equivalent for CO2) and the final blood pH, lactate and bicarbonate concentrations were similar for T and UT subjects. However, after VAR(HIGH), UT reduced P(MAX) (-14 +/- 1%; P < 0.05) while T did not. Our data suggest that endurance training confers adaptations to withstand the low pH provoked by VAR without losing cycling power, although this response is not due to differences in blood-respiratory buffering.
authors.affiliation: Exercise Physiology Laboratory at Toledo, University of Castilla-La Mancha, Avda. Carlos III, s/n, Toledo 45071, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Del Coso
authors.forename: Nassim
authors.initials: N
authors.lastname: Hamouti
authors.forename: Roberto
authors.initials: R
authors.lastname: Aguado-Jimenez
authors.forename: Ricardo
authors.initials: R
authors.lastname: Mora-Rodriguez
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D015308:Anaerobic Threshold / Q000502:physiology*; D001774:Blood Chemical Analysis; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D005082:Physical Exertion / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*; D012123:Pulmonary Ventilation / Q000502:physiology*; D055815:Young Adult