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.
Follow the pathway
One number. A connected system.
Choose a stage to see its role. These original diagrams are simplified teaching drawings, not anatomical scans.
Exchange at the lungs.
Air reaches the alveoli, the small air spaces where oxygen passes into blood. Much of that oxygen binds to haemoglobin in red blood cells. Moving air is only the beginning of the pathway.
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.
Continue learning
Understand the system behind the number.
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
Alvero-Cruz et al. · International Journal of Environmental Research and Public Health · 2020
Narrative review of 58 studies on performance-prediction models from 5 km to the marathon. Physiological, training and body-size variables contributed differently across distances; a single VO₂max value cannot predict every runner’s result. PubMed
Jones · The Journal of Physiology · 2024
A review of physiological resilience: endurance qualities can deteriorate during prolonged exercise, and the amount of deterioration differs between people. Read the review.