VO2 Max Explained — What It Is, Why It Matters, and How to Improve It
VO2 max is the most important single metric for aerobic fitness — and in 2026, your GPS watch estimates it automatically. Here we will give you a guide with VO2 Max , explained. Understanding what VO2 max means, whether wearable estimates are accurate, and how to systematically improve it can meaningfully change how you approach training.
This guide covers the science behind VO2 max in practical terms, what the numbers on your wearable actually mean, and the most effective training and nutrition strategies for improving it.
What Is VO2 Max?
VO2 max (maximal oxygen uptake) is the maximum rate at which your body can consume oxygen during intense exercise, expressed in millilitres of oxygen per kilogram of body weight per minute (ml/kg/min). It represents the ceiling of your aerobic engine — the higher your VO2 max, the greater your capacity for sustained high-intensity aerobic work.
Laboratory VO2 max testing involves running on a treadmill at increasing intensity while wearing a mask that measures oxygen consumption directly. It is the gold standard measurement but requires specialist equipment.
What Are Good VO2 Max Numbers?
Average VO2 max for untrained adults is approximately 35–40 ml/kg/min for men and 27–31 ml/kg/min for women. Recreational runners typically achieve 45–55 ml/kg/min for men and 40–50 ml/kg/min for women. Elite marathon runners commonly score 70–80+ ml/kg/min. More practically, a higher VO2 max correlates strongly with longevity — it is one of the strongest independent predictors of all-cause mortality across multiple large studies.
How Accurate Are Wearable VO2 Max Estimates?
Garmin, Polar, and Apple Watch all estimate VO2 max using algorithms that combine heart rate, pace, and running dynamics data. Independent research has shown that Garmin and Polar estimates correlate reasonably well with lab measurements for recreational runners, typically within 5–10% of actual VO2 max. They are useful as trend indicators — watching your estimated VO2 max improve over a training block is a meaningful signal, even if the absolute number has some margin of error.
How to Improve VO2 Max
VO2 max responds most strongly to high-intensity interval training (HIIT) and threshold training. The most effective sessions are intervals at 90–100% of VO2 max effort — approximately 3–8 minute intervals where you are working very hard but not sprinting. Classic formats include 4×4 minutes at near-maximal effort, 5×3 minutes at 5K race pace, and tempo intervals at lactate threshold pace.
Polarised training — where approximately 80% of volume is at easy aerobic intensity and 20% is at high intensity — has strong evidence for improving VO2 max in recreational athletes while minimising injury risk and overtraining.
Can Supplements Improve VO2 Max?
Several supplements have evidence supporting improved oxygen utilisation and delivery. L-Citrulline Powder improves nitric oxide production, enhancing blood flow and oxygen delivery to working muscles. Pre-Workout supplements containing caffeine improve time-to-exhaustion at VO2 max pace. Iron status is critical — even sub-clinical iron deficiency (low ferritin without anaemia) significantly impairs VO2 max and running economy. For a full breakdown, see our best supplements for runners guide.
VO2 Max and Longevity
A landmark study published in JAMA found that low cardiorespiratory fitness (estimated from VO2 max) was a stronger risk factor for all-cause mortality than smoking, hypertension, or diabetes. Moving from a low to moderate VO2 max category reduced mortality risk by approximately 50%. Improving your VO2 max through training is arguably the most powerful thing you can do for long-term health.
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