Threshold
The fraction of maximum capacity that can be sustained before physiological disturbance grows rapidly.
Free tool / 03 · Cardio
Understand a VO₂max result.
Enter a value you already have. The tool explains the unit, the likely measurement limits and which other qualities still matter for endurance. It does not estimate VO₂max from a questionnaire.
Existing result
VO₂max Explainer
What the number measures.
VO₂ is the rate at which the body uses oxygen. VO₂max is the highest rate reached during progressive, demanding exercise under the test conditions. The unit ml/kg/min means millilitres of oxygen used per kilogram of body mass each minute.
Relative VO₂max divides oxygen use by body mass, which makes comparison easier but introduces an assumption: oxygen use does not scale perfectly in a straight line with body size. Absolute VO₂ is reported in litres per minute and answers a different question about total oxygen use.
Air enters lungs
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Heart pumps blood
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Muscle extracts oxygen
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Mitochondria support ATP production
What VO₂max leaves out
Economy
The oxygen or energy cost of a given submaximal pace or workload.
Durability
How well physiology and performance are preserved as time and fatigue accumulate.
Use trends with discipline.
A true physiological change, ordinary day-to-day variation and measurement error can all move the reported value. Compare like with like: similar protocol, device, environment, preparation and time point. A watch estimate can be useful for a broad trend; it is not interchangeable with direct laboratory gas analysis.
A MET is a conventional resting-equivalent unit. One MET is often defined as 3.5 ml/kg/min, although actual resting metabolism varies. Dividing VO₂max by 3.5 gives a rough MET expression of maximum oxygen use, not a precise measure of how many times harder the body is working.
Evidence base
An integrated measure with important limits.
Joyner & Coyle · Journal of Physiology · 2008
Integrative review of maximal oxygen uptake, sustainable fraction and efficiency in endurance champions. PubMed
Blagrove et al. · 2020
Review of physiological and biomechanical determinants of distance-running performance, showing why VO₂max is one part of a larger model. PubMed