What is VO₂max?
Maximal oxygen uptake
VO₂max is the maximum amount of oxygen your body can take in and use during all-out exercise, and it's one of the best single measures of fitness.
Think of your body as a car engine. VO₂max is the size of the engine: how much fuel and air it can burn at full throttle. A bigger engine handles hills, and daily life, with more power in reserve.
Why it matters for aging
VO₂max depends on your whole oxygen chain: lungs taking in air, heart pumping blood, blood carrying oxygen, and muscle mitochondria using it. It's measured precisely in a lab with a mask during a treadmill or bike test; fitness watches give rough estimates.
It tends to decline with age, partly because of aging itself and largely because people move less. Both steady cardio and harder interval training raise it, with harder intervals giving the most gain per minute.
A common myth
VO₂max is only for athletes and doesn't matter for normal people.
In a study of more than 122,000 adults, people with the lowest fitness had about five times the risk of dying during follow-up compared with the fittest, a link as strong as smoking. VO₂max falls with age and inactivity, but training raises it at any age.
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Updated Nov 9, 2026 · All terms