title: Oxygen uptake kinetics during moderate and heavy intensity exercise in humans: the influence of hypoxia and training status.
abstract: This study examined the influence of moderate hypoxia on the oxygen uptake (V.O(2)) kinetic response (primary time constant and slow component amplitude) during moderate and heavy cycle exercise in twenty-seven male subjects with various training status. Nine endurance trained (21.5 +/- 2.6 yr), nine sprint trained (22.9 +/- 5.7 yr), and nine untrained controls (24.0 +/- 4.4 yr) completed incremental tests to exhaustion in normoxia (inspired gas concentration or FIO (2) = 21 % O(2)) and hypoxia (FIO (2) = 13 % O(2)) to establish the FIO (2)-specific ventilatory threshold (VT) and maximal VO(2). Subsequently, the subjects performed repeated constant work rate cycling exercises during 7 min at moderate intensity (80 % of FIO (2)-specific VT) and heavy intensity (midway between the FIO (2) specific VT and maximal VO(2)). Pulmonary gas exchange was measured breath-by-breath during all exercise sessions. For both moderate and heavy intensities, the time constant of the primary VO(2) component was significantly (p < 0.05) slowed by approximately 25 to 30 % in hypoxia compared to normoxia to the same extent in the three groups. Hypoxia produced a more important decrease in the amplitude of the slow component in endurance athletes (- 36 %) than in sprinters (- 30 %) and controls (- 12 %). These results suggest that both primary and slow components of VO(2) kinetics during the adjustment to moderate- and heavy-intensity exercise are sensitive to hypoxia while training status tended to modulate partly the slow component amplitude.
authors.affiliation: Laboratoire de Physiologie de l'Exercice Musculaire, Faculté des Sports et de l'Education Physique, Université d'Orléans, France.
authors.forename: C
authors.initials: C
authors.lastname: Cleuziou
authors.forename: S
authors.initials: S
authors.lastname: Perrey
authors.forename: A M
authors.initials: AM
authors.lastname: Lecoq
authors.forename: R
authors.initials: R
authors.lastname: Candau
authors.forename: D
authors.initials: D
authors.lastname: Courteix
authors.forename: P
authors.initials: P
authors.lastname: Obert
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D007700:Kinetics; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010806:Physical Education and Training; D012420:Running / Q000502:physiology