Scientific article

Cardiac output, O2 delivery and VO2 kinetics during step exercise in acute normobaric hypoxia

Published inRespiratory physiology & neurobiology, vol. 186, no. 2, p. 206-213
Publication date2013

We hypothesised that phase II time constant (τ2) of alveolar O2 uptake ( [Formula: see text] ) is longer in hypoxia than in normoxia as a consequence of a parallel deceleration of the kinetics of O2 delivery ( [Formula: see text] ). To test this hypothesis, breath-by-breath [Formula: see text] and beat-by-beat [Formula: see text] were measured in eight male subjects (25.4±3.4yy, 1.81±0.05m, 78.8±5.7kg) at the onset of cycling exercise (100W) in normoxia and acute hypoxia ( [Formula: see text] ). Blood lactate ([La]b) accumulation during the exercise transient was also measured. The τ2 for [Formula: see text] was shorter than that for [Formula: see text] in normoxia (8.3±6.8s versus 17.8±3.1s), but not in hypoxia (31.5±21.7s versus 28.4 5.4±5.4s). [La]b was increased in the exercise transient in hypoxia (3.0±0.5mM at exercise versus 1.7±0.2mM at rest), but not in normoxia. We conclude that the slowing down of the [Formula: see text] kinetics generated the longer τ2 for [Formula: see text] in hypoxia, with consequent contribution of anaerobic lactic metabolism to the energy balance in exercise transient, witnessed by the increase in [La]b.

  • Anoxia/physiopathology
  • Cardiac Output/physiology
  • Energy Metabolism/physiology
  • Exercise/physiology
  • Humans
  • Kinetics
  • Male
  • Oxygen/metabolism
  • Oxygen Consumption/physiology
Citation (ISO format)
LADOR, Frédéric et al. Cardiac output, O2 delivery and VO2 kinetics during step exercise in acute normobaric hypoxia. In: Respiratory physiology & neurobiology, 2013, vol. 186, n° 2, p. 206–213. doi: 10.1016/j.resp.2013.01.017
Main files (1)
Article (Published version)
ISSN of the journal1569-9048

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