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

Abstract

Introduction: During maximal ramp-incremental exercise (RIE), the oxygen uptake–power output relationship ((Formula presented.) O2gain) may deviate from linearity near exhaustion. An increased oxygen cost of ventilation ((Formula presented.) O2VENT) is a plausible but under-quantified contributor. This study tested a non-linear multi-factorial model using measured (Formula presented.) O2VENT and six predictors: resting expired ventilation ((Formula presented.) E), weight, height, age, (Formula presented.) O2 peak, and maximal heart rate (HRMax) to 1) estimate (Formula presented.) O2VENT and its contribution to maximal oxygen uptake ((Formula presented.) O2max) in an independent dataset and 2) determine whether correcting (Formula presented.) O2 by (Formula presented.) O2VENT ((Formula presented.) O2VCORR) alters (Formula presented.) O2max and (Formula presented.) O2gain estimates. Methods: Published data from 42 participants (11 women, 31 men; 29 ± 6.5 years; (Formula presented.) 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 (Formula presented.) O2VCORR, which was compared with uncorrected (Formula presented.) O2 across six %Wpeak intensities using repeated-measures ANOVA and final 30 s slope analysis. Results: The model explained 81% of (Formula presented.) O2VENT variance (adjusted R2 = 0.78). (Formula presented.) O2VENT represented 17.43% ± 3.58% of (Formula presented.) O2 at (Formula presented.) O2max. Across 35%–100% Wpeak, (Formula presented.) O2VCORR 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 (Formula presented.) O2 (p < 0.001), with the final-30 s (Formula presented.) O2 slope attenuated following correction (p = 0.002). Conclusion: The internally validated model revealed (Formula presented.) O2VENT may contribute to a significant fraction of (Formula presented.) O2 near exhaustion.