The maximum rate of oxygen consumption per unit of time, a limit for how much energy you can expend through aerobic processes.
VO2 Max (VO2MAX, or is the maximum rate of oxygen consumption per unit of time. It’s the limit to how much energy you can expend through aerobic means. It’s not what enables you to sprint at full speed for 30 seconds. It’s what enables you to run a mile as fast as you can. It’s related to the final stage of the 3 Types of Energy Supply in Mammals.
VO2 Max is a powerful predictor of all-cause mortality.
According to the Apple Health App (which cites its source, too) - these are the ‘healthy’ ranges:
Measuring
Properly measuring VO2 Max involves a face mask and a treadmill. There are other means of testing it, but none of them are perfectly predictive and they all boil down to “how fast can you run over a many-minute period?“.
It’s measured in mL/(kg*min).
Increasing
Do cardiovascular exercise that causes you to breath hard. Maintain that state as long as you can. Do that often.
A simple procedure per Outlive is to alternate between 4 minutes on and 4 minutes off of running very fast (but not sprinting) and letting your heart rate recover between sessions.
Averages
Average healthy male is 35-40 mL/(kg * min). Female average is 27-31 mL/(kg * min). Training can raise this up to ~80 mL/(kg * min), if you’re “elite”.