Research article - (2011)10, 584 - 589
Oxygen Uptake Kinetics During Incremental- and Decremental-Ramp Cycle Ergometry
Fadil Özyener1,2,, Harry B. Rossiter1,3, Susan A. Ward4, Brian J. Whipp1,4
1Dept of Physiology, St George's Hospital Medical School, London, United Kingdom
2Dept of Physiology, Uludag University Medical School, Bursa, Turkey
3Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
4Human Bio-Energetics Research Centre, Crickhowell, Powys, United Kingdom

Fadil Özyener
✉ Uludag University, Medical School, Department of Physiology, 16059 Bursa, Turkey
Email: fozyener@uludag.edu.tr
Received: 28-06-2011 -- Accepted: 01-08-2011
Published (online): 01-09-2011

ABSTRACT

The pulmonary oxygen uptake (VO2) response to incremental-ramp cycle ergometry typically demonstrates lagged-linear first-order kinetics with a slope of ~10-11 ml·min-1·W-1, both above and below the lactate threshold (θL), i.e. there is no discernible VO2 slow component (or “excess” VO2) above θL. We were interested in determining whether a reverse ramp profile would yield the same response dynamics. Ten healthy males performed a maximum incremental -ramp (15-30 W·min-1, depending on fitness). On another day, the work rate (WR) was increased abruptly to the incremental maximum and then decremented at the same rate of 15-30 W.min-1 (step-decremental ramp). Five subjects also performed a sub-maximal ramp-decremental test from 90% of θL. VO2 was determined breath-by-breath from continuous monitoring of respired volumes (turbine) and gas concentrations (mass spectrometer). The incremental-ramp VO2-WR slope was 10.3 ± 0.7 ml·min-1·W-1, whereas that of the descending limb of the decremental ramp was 14.2 ± 1.1 ml·min-1·W-1 (p < 0.005). The sub-maximal decremental-ramp slope, however, was only 9. 8 ± 0.9 ml·min-1·W-1: not significantly different from that of the incremental-ramp. This suggests that the VO2 response in the supra-θL domain of incremental-ramp exercise manifest not actual, but pseudo, first-order kinetics.

Key words: Oxygen uptake-work rate gain, incremental-ramp exercise, decremental-ramp exercise, system linearity.

Key Points
  • The slope of the decremental-ramp response is appreciably greater than that of the incremental.
  • The response dynamics in supra-θ domain of the incremental-ramp appear not to manifest actual first-order kinetics.
  • The mechanisms underlying the different dynamic response behaviour for incremental and decremental ramps are presently unclear.








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