VO2 max: why it's a mortality biomarker and how training raises it

VO2 max (maximal oxygen uptake) is the highest rate at which your body can take in, deliver, and use oxygen during exhausting exercise. It's measured in millilitres of oxygen per kilogram of body weight per minute (ml/kg/min). It is also one of the most consistently powerful predictors of all-cause mortality in the published literature.

Why it matters#

A 2018 JAMA Network Open analysis of 122,007 patients tested over decades reported that low cardiorespiratory fitness (measured by treadmill testing) was associated with higher mortality risk than smoking, hypertension, or diabetes. The relationship was dose-dependent: every increment of measured fitness predicted lower mortality, with no obvious upper plateau within the studied range.

This isn't unique to one cohort. Similar findings appear in the Cooper Clinic, Aerobics Center Longitudinal Study, the FRIEND registry, and the European Aerobics Center cohorts. The size of the effect dwarfs most lifestyle interventions you can measure cleanly.

Reference values#

VO2 max is age- and sex-dependent. Rough mid-range values for adults:

• 20s–30s healthy untrained: 35–45 ml/kg/min (men), 30–40 (women)
• 40s–50s: declines by roughly 10% per decade in untrained people
• Trained endurance athletes: 60–80+ ml/kg/min
• Elite endurance athletes (e.g. cross-country skiers): 80–95+ ml/kg/min

The decline with age is real but plastic. Well-trained masters athletes maintain VO2 max far better than sedentary peers.

How to raise it#

The training literature is consistent on a few points:

• High-intensity intervals work fastest. 4×4 minute intervals at 90–95% of max heart rate, with 3 minutes of active recovery between, is the most-studied protocol (originating in Norwegian university lab work; popularised by Gjøvaag, Wisløff, and others).
• A solid aerobic base extends the ceiling. Easy training (zone 2) builds the cardiovascular substrate that lets intervals matter.
• Time-efficient minimum doses exist. A 2018 systematic review found measurable VO2 max improvements with as little as 2 sessions per week of HIIT, sustained over 8–12 weeks.

A reasonable beginner protocol#

• 2 zone 2 sessions per week of 30–60 minutes
• 1 interval session per week (e.g. 4×4 minute on, 3 minute active recovery)
• Build over 8–12 weeks before measuring change

VO2 max responds to training. A 10–20% increase over a few months is realistic for someone who was sedentary. Trained athletes have smaller relative gains but still respond.

Measurement#

Lab tests with gas exchange (CPET) are the gold standard. The cost in the UK is typically £150–£300 privately; NHS access is generally only for cardiac rehabilitation. Field estimates exist:

• Cooper 12-minute run distance → VO2 max estimate (decent for trained adults)
• 1.5-mile run time
• Bruce treadmill protocol
• Some wearables estimate VO2 max from running pace and heart rate: accuracy versus CPET is variable; trends over months are more reliable than single readings.

What this isn't#

A high VO2 max isn't a free pass. Cardiovascular risk depends on blood pressure, lipids, smoking, glucose control, and many other factors. The epidemiology shows VO2 max is a strong correlate of long-term outcome, not the only one.

It's also not infinite. Training stress + recovery + sleep + nutrition all matter; you can't out-interval a bad week.

The honest read: VO2 max is one of the few biomarkers where the evidence for both its predictive power and its trainability is unusually strong. Raising it is one of the better-evidenced things an adult can do for long-term health outcomes.