What it means
A higher VO2 max means your heart, lungs and muscles deliver and use oxygen well. It is strongly linked with long-term health in large studies.
Lab tests measure it directly on a treadmill or bike. Watches and field tests, such as a timed run or walk, give estimates that can be off by a meaningful margin.
Because VO2 max is expressed per kilogram of body weight, losing weight can raise the number even if your heart and lungs did not change. Training is what raises the absolute capacity.
Even short bouts of brisk walking or stair climbing can improve VO2 max over a few months for people who are starting from a low base. Track the same test over time for the clearest picture.
Why it matters
The VO2 max estimator lets you track fitness gains alongside weight change.