Delayed Kinetics of V̇O₂ in the Transition from Prior Exercise. Evidence for O₂ Transport Limitation of V̇O₂ Kinetics: A Review*

Abstract

The influence of prior exercise state on the kinetics of V̇O₂, V̇_E, and HR was studied in six subjects. The exercise conditions tested were square wave increases in work rate from rest to 80% of the work rate at anaerobic threshold (AT), from O W loadless pedaling to 80% AT, from rest to 40% AT, and from 40% to 80% AT. The kinetic response was evaluated by the time constant (τ) and mean response time (MRT = time to achive 63% response) as determined by nonlinear regression. For both V̇O₂ and HR, τ and MRT were not significantly different in the rest or O W to 80% AT tests, but were significantly faster in the rest to 40% AT test and significantly slower in the 40% to 80% AT test than the rest and O W to 80% AT tests. The τ for V̇_E was significantly slower in the 40% to 80% AT tests than in the other tests. The coincident variation of HR and V̇O₂ kinetics is taken as support for the hypothesis that V̇O₂ kinetics are controlled by oxygen transport. Evidence from the literature that supports both the oxygen transport and the oxygen utilization for the control of V̇O₂ kinetics is reviewed.

oxygen uptake - exercise - heart rate - ventilation - vasodilatation - muscle blood flow - muscle metabolism