The off-transient pulmonary oxygen uptake (V(over dot)(O2)) kinetics following attainment of a particular V(over dot)(O2) during heavy-intensity exercise in humans


Cunningham D., St Croix C., Paterson D., Ozyener F. , Whipp B.

EXPERIMENTAL PHYSIOLOGY, vol.85, no.3, pp.339-347, 2000 (Journal Indexed in SCI) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 85 Issue: 3
  • Publication Date: 2000
  • Doi Number: 10.1111/j.1469-445x.2000.01919.x
  • Title of Journal : EXPERIMENTAL PHYSIOLOGY
  • Page Numbers: pp.339-347

Abstract

The oxygen uptake response to moderate-intensity exercise (i.e. < anaerobic threshold (theta(an))) has been characterised with a gain (i.e, response amplitude per increment of work rate) and time constant that do not vary appreciably at different work rates or between the on- and off-transients. Above theta(an), the response becomes more complex with an early component that typically projects to a value that has a gain similar to that of the < theta(an) response, but which is supplemented by the addition of a delayed slow kinetic component. We therefore established a constant target (V)over dot(O2) ((V)over dot(O2)(1)) for each subject such that with different imposed work rates the contribution to (V)over dot(O2)(1) from the slow phase varied over a wide range. Work rates were chosen so that (V)over dot(O2)(1) was attained at 2-24 min. Five subjects (aged 21-58 years) cycled at four to five different work rates. (V)over dot(O2) was measured breath-by-breath, at (V)over dot(O2)(1) the work rate was abruptly reduced and the subject recovered by cycling unloaded for 15 min. Unlike the on-transient, for which the slow component shows a long delay, the off-transient was best fitted as two simultaneous exponential components. The slower off-transient component had a small amplitude and long time constant, but did not differ significantly among the various tests. The off-transient kinetics far (V)over dot(O2) therefore was independent of the magnitude of the contribution to the slow phase from the on-transient kinetics.