2018JAMA Network Open
Mandsager et al.
122,007 adults
Treadmill fitness was linked to survival with no upper limit. Low fitness carried as much risk as smoking, diabetes or heart disease; elite performers lived longest.
Find on PubMed ↗Research library · Heart & fitness
VO2 max: your engine size
VO2 max is the most oxygen your body can take in and use at full effort. In large studies it predicts how long you'll live better than almost any other single measurement, and it's very trainable at any age.
Strong evidence5×higher risk of death for the least fit vs the fittestMandsager 2018, JAMA Netw Open, 122,007 people
−13%death risk for every 3.5 mL/kg/min (1 MET) of fitness you gainKodama 2009, JAMA, 102,980 people
4×risk of death for the least fit vs extremely fit US veteransKokkinos 2022, JACC, 750,302 people
01
The basics
What VO2 max actually measures
Every cell in your body needs oxygen to make energy. VO2 max is the ceiling: the largest volume of oxygen (in millilitres) your body can use per kilogram of body weight per minute when you are working as hard as you possibly can.
It's a chain, and the weakest link sets your number. Your lungs bring air in, your heart pumps oxygen-rich blood out, your blood carries the oxygen on haemoglobin, and your muscles pull it out and burn it in their mitochondria. In most healthy people the heart's pumping power is the main limit.
Without training, VO2 max falls by roughly 10% each decade after about age 30, and faster after 70. Once it drops below about 18 mL/kg/min, everyday things like climbing stairs or carrying shopping become hard. That is why a high VO2 max in midlife works like a pension: it keeps you above that line for longer.
Fitness across a lifetime
Illustration based on typical ageing curves. Training lifts the whole line, keeping you above the level needed to live independently for 10–20 years longer.
02
How it works
How oxygen gets from the air to your muscles
1
Lungs
Air reaches 300 million tiny air sacs, where oxygen crosses into the blood.
2
Heart
Each beat pushes out a stroke volume of blood. Training makes this volume bigger.
3
Blood
Haemoglobin in red blood cells carries the oxygen through your arteries.
4
Muscle
Capillaries deliver it to mitochondria, which burn it to make energy (ATP).
03
Measure it
How to measure it
- Lab test (most accurate): you run or cycle with a mask on while the effort ramps up until you can't go on. The machine measures the oxygen you breathe in and out.
- Smartwatch estimate: Apple Watch, Garmin and others estimate it from your heart rate and pace during outdoor walks or runs. Useful for trends, but it can be several points off.
- 12-minute run (Cooper test): run as far as you can in 12 minutes on a flat track. Try the calculator below.
Try your number
LowBelow averageAverageGoodExcellent
1565
Rough bands for a man in his 40s, based on Cooper Institute and ACSM norms. For women subtract about 6–8. Each decade older, subtract about 3–4.
12-minute run calculator
Estimated VO2 max: —
Cooper formula: (metres − 504.9) ÷ 44.73. A rough field estimate; pace yourself and stop if you feel unwell.
04
What the research says
The key studies
2009JAMA
Kodama et al.
33 studies, 102,980 people
Each 1-MET (3.5 mL/kg/min) higher fitness meant 13% lower death risk and 15% lower heart disease risk.
Find on PubMed ↗2022J Am Coll Cardiol
Kokkinos et al.
750,302 US veterans
Across all ages, sexes and races, the least fit had about 4 times the risk of death of the most fit. Being unfit was a bigger risk than smoking.
Find on PubMed ↗2007Med Sci Sports Exerc
Helgerud et al.
40 men
8 weeks of 4×4-minute intervals raised VO2 max by about 7%; steady moderate running at the same total work barely moved it.
Find on PubMed ↗2018Circulation
Howden et al.
53 middle-aged adults
Two years of structured training (including one interval session a week) raised VO2 max by 18% and reversed age-related stiffening of the heart.
Find on PubMed ↗1999J Appl Physiol
Bouchard et al. (HERITAGE)
481 people from 98 families
About half the variation in how much people improved came from genes, but nearly everyone improved with training.
Find on PubMed ↗05
Take action
How to raise it
The best results come from mixing lots of easy aerobic work with a small amount of very hard intervals.
- 1
Build the base: Zone 2
2–4 hours a week at an easy pace where you can still speak in full sentences. This grows mitochondria and capillaries.
- 2
Add one or two 4×4 sessions
Warm up, then 4 minutes hard (85–95% of max heart rate), 3 minutes easy. Repeat 4 times. This stretches the heart's stroke volume.
- 3
Any cardio counts
Running, cycling, rowing, swimming, brisk uphill walking or stair climbing all work. Pick what you'll keep doing.
- 4
Progress slowly
Add about 10% more time per week, and take an easier week every 4th week.
- 5
Re-test every 8–12 weeks
Untrained people often gain 10–20% in the first few months.
A sample week
MonZone 2 · 45 min
TueStrength
Wed4×4 intervals
ThuZone 2 · 45 min
FriStrength
SatLong Zone 2 · 60–90 min
SunRest or walk
06
Myth or fact
Common myths, checked
✕ MythYou can't improve it after 50 or 60.
✓ FactOlder adults respond to training too. People in their 70s and 80s improve their VO2 max in trials, and the gains matter most at that age.
✕ MythIt only matters for athletes.
✓ FactThe biggest drop in risk comes from going from the lowest fitness group to just below average, not from becoming elite.
✕ MythMy watch number is exact.
✓ FactWatches estimate it. Use the trend over months rather than any single number.
✕ MythLong slow cardio is all you need.
✓ FactEasy cardio builds the base, but a little high-intensity work is what pushes the ceiling up.
07
Questions
Frequently asked
How fast can I improve?
Beginners often see 10–20% in 3–6 months. Already fit people improve more slowly, a few percent a year.
Is VO2 max genetic?
Partly. Studies of families suggest about half of your starting level and how fast you improve comes from genes. But almost everyone improves with the right training.
Does losing weight raise it?
Yes, because it's measured per kilogram. Losing fat raises the number even if your heart and lungs don't change, though training improves both.
Is high-intensity training safe?
For most healthy people, yes. If you have heart disease, chest pain or haven't exercised in years, talk to a doctor and build an easy base first.
08
Sources
References and related topics
- Mandsager et al. (2018). JAMA Network Open. 122,007 adults. PubMed ↗
- Kodama et al. (2009). JAMA. 33 studies, 102,980 people. PubMed ↗
- Kokkinos et al. (2022). J Am Coll Cardiol. 750,302 US veterans. PubMed ↗
- Helgerud et al. (2007). Med Sci Sports Exerc. 40 men. PubMed ↗
- Howden et al. (2018). Circulation. 53 middle-aged adults. PubMed ↗
- Bouchard et al. (HERITAGE) (1999). J Appl Physiol. 481 people from 98 families. PubMed ↗