VO2 Max Explained
VO2 max is the gold standard measure of cardiovascular fitness. Here's what it means, what affects it, and — most importantly — why obsessing over the number misses the point.
What Is VO2 Max?
VO2 max measures the maximum volume of oxygen your body can consume during intense exercise. Think of it as your engine's maximum horsepower — the absolute ceiling of your aerobic capacity.
It's expressed in ml/kg/min (millilitres of oxygen per kilogram of bodyweight per minute). A higher number means your cardiovascular system can deliver and use more oxygen, allowing you to work harder aerobically.
VO2 Max Ranges
Men (ml/kg/min)
Below average. Significant room for improvement with any consistent cardio.
Average for a sedentary adult. Basic fitness level.
Above average. Regular exerciser level.
Well-trained recreational athlete.
Competitive endurance athletes. Top percentile.
Women (ml/kg/min)
Below average. Any consistent cardio will help significantly.
Average for a sedentary adult.
Above average. Regular exerciser level.
Well-trained recreational athlete.
Competitive endurance athletes.
What Affects VO2 Max
Genetics
Sets your ceiling. Some people naturally have higher VO2 max potential. But most people are so far from their genetic limit that this barely matters practically.
Training
The biggest lever you can pull. Consistent aerobic training (running, cycling, swimming) is the primary driver of VO2 max improvement.
Age
VO2 max naturally declines about 1% per year after age 30. But trained 50-year-olds often have higher VO2 max than untrained 25-year-olds.
Body composition
Since VO2 max is per kg of bodyweight, losing excess fat improves it even without fitness changes. Another reason body composition matters.
Altitude
Living at high altitude can improve oxygen-carrying capacity over time. Not practically useful for most people.
How to Improve It
80% of training
Easy-pace running
Builds your aerobic base — capillary density, mitochondria, heart stroke volume. The foundation everything else is built on. Most underrated method.
1x per week
VO2 max intervals
Hard intervals at 90-95% of max heart rate (e.g., 4-6 × 3-5min with equal rest). Directly challenges your oxygen system. Very effective but very fatiguing.
1x per week
Tempo runs
Sustained effort at lactate threshold (comfortably hard). Improves your ability to sustain a high percentage of your VO2 max for longer.
3-5x per week
Consistent frequency
Running 4 times per week is dramatically more effective than 2 times per week at the same total volume. Frequency matters more than individual session length.
Watch Estimates
Your Garmin/Apple Watch VO2 max is an estimate, not a measurement. Use it for trend tracking — is it going up over months? — not as an absolute value. Don't compare your watch number to lab-tested athletes.
Don't Over-Optimise
VO2 max is one marker of fitness. You don't need to specifically "train VO2 max" — consistent running with occasional hard efforts improves it naturally. Chasing the number leads to overtraining. Focus on the training, not the metric.
Health Perspective
VO2 max is one of the strongest predictors of longevity and all-cause mortality. You don't need elite levels — moving from "poor" to "good" provides the biggest health benefit. Any regular cardio helps.