Oxygen uptake kinetics during incremental- and decremental-ramp cycle ergometry

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. © journal of sports science and medicine.