Does exercise near or above peak VO2 result in slower oxygen uptake kinetics compared to subventilatory threshold exercise in healthy young men?
Oxygen uptake kinetics during very heavy exercise are consistent with a model in which the cardiovascular system is compromised.
We tested the hypothesis that kinetics of O 2 uptake (V˙o 2 ) measured in the transition to exercise near or above peakV˙o 2 (V˙o 2 peak ) would be slower than those for subventilatory threshold exercise. Eight healthy young men exercised at ∼57, ∼96, and ∼125%V˙o 2 peak . Data were fit by a two- or three-component exponential model and with a semilogarithmic transformation that tested the difference between required V˙o 2 and measuredV˙o 2 . With the exponential model, phase 2 kinetics appeared to be faster at 125% V˙o 2 peak time constant (τ 2 ) = 16.3 ± 8.8 (SE) s than at 57%V˙o 2 peak (τ 2 = 29.4 ± 4.0 s) but were not different from that at 96%V˙o 2 peak exercise (τ 2 = 22.1 ± 2.1 s).V˙o 2 at the completion of phase 2 was 77 and 80%V˙o 2 peak in tests predicted to require 96 and 125%V˙o 2 peak . WhenV˙o 2 kinetics were calculated with the semilogarithmic model, the estimated τ 2 at 96%V˙o 2 peak (49.7 ± 5.1 s) and 125%V˙o 2 peak (40.2 ± 5.1 s) were slower than with the exponential model. These results are consistent with our hypothesis and with a model in which the cardiovascular system is compromised during very heavy exercise.
Hughson et al. (Mon,) studied this question.