Examination of oxygen uptake kinetics in decremental load exercise by a numerical computation model

Abstract

The purpose of this study was to establish a numerical computation model for estimation of oxygen uptake (V̇O2) kinetics in decremental load exercise (DLE) starting from a work rate (WR) above the ventilatory threshold (>VT). In the model, WR in DLE were separated into several steps (constant load exercise, CLE) of which the durations increased step by step. V̇O2 kinetics in each step was estimated using an exponential equation, and the sum of V̇O2 values from all steps at a given time was regarded as simulated V̇O2 in DLE. In the model, the time constants were set symmetrically in a step VT at onset and offset (τoff) of exercise. As a result, simulated V̇O2 qualitatively, but not quantitatively, approximated measured V̇O2. Consequently, we incorporated a new model in which a step >VT was subdivided into several parts. Although there was a slight difference quantitatively, the interval of subdivision of 3.0 min and τoff of 2.8 min allowed for qualitative approximation. The numerical computation model adopted in this study is useful for estimation of V̇O2 kinetics during DLE starting from high intensity (>VT).