Modeling V̇o₂ on-kinetics based on intensity-dependent delayed adjustment and loss of efficiency (DALE)

Area of Science:

• Exercise Physiology
• Mathematical Modeling
• Human Performance

Background:

• Oxygen uptake (V̇o₂) kinetics describe the body's dynamic response to exercise.
• Existing models often fail to accurately represent V̇o₂ on-kinetics across different exercise intensities.
• Misconceptions persist regarding the attainment of a steady state in V̇o₂, particularly in heavy and severe exercise domains.

Purpose of the Study:

• To present and evaluate a novel mathematical model of V̇o₂ on-kinetics.
• To differentiate V̇o₂ adaptations in heavy and severe exercise domains.
• To provide a framework for assessing oxygen costs without assuming constant energy efficiency.

Main Methods:

• Development of a new minimalistic integrated model for V̇o₂ on-kinetics.
• Breath-by-breath V̇o₂ data collection from eight subjects during step cycling transitions (moderate, heavy, severe domains).
• Comparison of the new model against the conventional three-phase model using residual analysis and information criteria (BIC, AICc).

Main Results:

• The new model demonstrated no systematic deviations in residual analysis, similar to the conventional model.
• Bayesian Information Criterion (BIC) favored the new model, indicating a better fit.
• The proposed model predicts attainable steady-state V̇o₂ in moderate/heavy domains and no steady-state in the severe domain, clarifying slow component behavior.

Conclusions:

• The new V̇o₂ on-kinetics model offers a more mechanistically informed approach.
• It accurately distinguishes kinetic adaptations across exercise intensity domains.
• This model advances the assessment of oxygen costs, especially during severe exercise where efficiency may vary.