VO2 max is the maximum rate at which your body can take in and use oxygen during intense exercise, measured in millilitres of oxygen per kilogram of body weight per minute. It's one common marker of aerobic fitness and is often used to estimate race potential, though pacing, running economy, and mental toughness matter too.
It's a measure of how much oxygen your body can use during maximal effort, reflecting how well your heart, lungs, and muscles work together. Higher values generally indicate stronger aerobic fitness.
Structured hard efforts like interval training, run at a pace you can sustain for only several minutes, are the most direct way to raise it. Consistent overall training volume over months also contributes.
Many GPS running watches and fitness apps provide an estimated VO2 max based on your pace and heart rate data. It's a rough estimate, not a lab-accurate measurement, so treat it as a trend indicator rather than an exact number.
It's correlated with performance, but not the whole story. Two runners with similar VO2 max can race very differently depending on running economy, pacing discipline, and race-day fuelling.