VO2max

VO2max is the most oxygen your body can use per minute and per kilo, in ml/kg/min. The higher it is, the stronger your aerobic engine. Maximal aerobic speed is the running speed that matches it.

• Apple Watch estimates it after your outdoor runs and walks, and Kadence can read it from Health.
• It rises with consistency, endurance and intervals, and slowly falls when you stop.

It is a fitness marker, not a grade: compare it with yourself over time.