What is VO2max and what's a good number for a man over 40?

VO2max is the maximum rate of oxygen consumption during maximal exertion, expressed in milliliters of oxygen per kilogram of bodyweight per minute (mL/kg/min), for men aged 40–49, excellent fitness is above 43 mL/kg/min, good is 37–43, average is 31–37, fair is 24–31, and below 24 mL/kg/min is the low fitness range associated with the highest cardiovascular mortality quintile ([American College of Sports Medicine Fitness Categories, 2022]).

The clinical significance is more dramatic than a fitness classification chart suggests. The Peter Attia framing is accurate: VO2max is a better predictor of cardiovascular mortality than blood pressure, cholesterol, or body weight in multiple large cohort studies. The longevity benefit is continuous, there is no plateau where "more fitness produces diminishing mortality benefit." The gradient is steepest in the transition from very low to low/average fitness, the men with the most to gain from improving their VO2max are the ones currently in the bottom two quintiles.

Honesty Scale: Solid (1). VO2max as a mortality predictor is among the most replicated findings in exercise cardiology.

What to do: Know your VO2max. If your physician offers a graded exercise test (GXT/exercise stress test), this measures both cardiovascular function and fitness. If not, the Rockport Walk Test gives a reasonable estimate. If your estimated VO2max is below 30 mL/kg/min at age 40–49, this is your most important health number to improve.

For the full picture, read The VO2max/Zone 2 Deep Dive