An evidence-based multi-factorial model to predict the oxygen cost of ventilation during ramp-incremental cycle...

During maximal ramp-incremental exercise (RIE), the oxygen uptake-power output relationship ( $\dot{V}$ O₂gain) may deviate from linearity near exhaustion. An increased oxygen cost of ventilation ( $\dot{V}$ O_2VENT) is a plausible but under-quantified contributor. This study tested a non-linear multi-factorial model using measured $\dot{V}$ O_2VENT and six predictors: resting expired ventilation ( $\dot{V}$ _E), weight, height, age, $\dot{V}$ O₂ peak, and maximal heart rate (HRMax) to 1) estimate $\dot{V}$ O_2VENT and its contribution to maximal oxygen uptake ( $\dot{V}$ O₂max) in an independent dataset and 2) determine whether correcting $\dot{V}$ O₂ by $\dot{V}$ O_2VENT ( $\dot{V}$ O_2VCORR) alters $\dot{V}$ O₂max and $\dot{V}$ O₂gain estimates.

Published data from 42 participants (11 women, 31 men; 29 ± 6.5 years; $\dot{V}$ O₂max = 4.02 ± 1.06 L min^-1) were used to derive the model. Leave-one-out cross-validation (LOOCV) was used to assess validity, with predictive accuracy and coefficient stability evaluated via bootstrap resampling. The model was applied to an independent RIE dataset to generate $\dot{V}$ O_2VCORR, which was compared with uncorrected $\dot{V}$ O₂ across six %Wpeak intensities using repeated-measures ANOVA and final 30 s slope analysis.

The model explained 81% of $\dot{V}$ O_2VENT variance (adjusted R ² = 0.78). $\dot{V}$ O_2VENT represented 17.43% ± 3.58% of $\dot{V}$ O₂ at $\dot{V}$ O₂max. Across 35%-100% Wpeak, $\dot{V}$ O_2VCORR values (L·min^-1) increased with intensity (1.77 ± 0.43, 2.68 ± 0.57, 3.43 ± 0.72, 3.72 ± 0.79, 3.84 ± 0.86, and 3.92 ± 0.82) but remained significantly lower than uncorrected $\dot{V}$ O₂ (p < 0.001), with the final-30 s $\dot{V}$ O₂ slope attenuated following correction (p = 0.002).

The internally validated model revealed $\dot{V}$ O_2VENT may contribute to a significant fraction of $\dot{V}$ O₂ near exhaustion.