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 evidenceUpdated Oct 2026 · 3 new studies5×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
New in 2025–26
What the newest research adds
New work shows that moving out of the least-fit group brings most of the benefit, that being fit largely cancels out the extra risk of carrying more weight, and that good fitness is also linked to a lower risk of dementia.
The new studies, in order
Every study added to this page since January 2025. Green rings are the strongest evidence: large trials or meta-analyses.
Fitness matters more than weight
Weeldreyer et al., 2025, 20 studies, about 399,000 adults. Risk of death compared with fit people of normal weight (1 = same risk).
NewMar 2025Prog Cardiovasc Dis
Tari et al. (Generation 100)
1,565 adults aged 70 to 77, 5 years
Compared with unfit older adults, moderately fit men had a 66% lower risk of death and moderately fit women a 59% lower risk. Being fitter than 'moderate' gave no extra drop in risk, so the big win is getting out of the bottom group.
Good evidenceRead the source ↗
NewFeb 2025Br J Sports Med
Weeldreyer et al.
20 studies, about 399,000 adults
Unfit people had roughly double the risk of death whatever their weight. People with obesity who were fit had no clear extra risk of death compared with fit people of normal weight (hazard ratio 1.11, not significant). Published online late 2024.
Good evidenceRead the source ↗
NewMay 2026Nat Ment Health
Díaz-Goñi et al.
27 studies, about 4 million adults
The fittest people had a 39% lower risk of dementia than the least fit. Each 1-MET rise in fitness was linked to about 19% lower dementia risk. Links with depression were weaker and the evidence less certain.
Good evidenceRead the source ↗
What this changes for you
The biggest win is getting out of the least-fit group, at any weight. If you're starting from low fitness, steady cardio most days will do more for your risk than chasing an elite number, and it may protect your brain as well as your heart.
06
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
07
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.
08
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.
09
Test yourself
True, partly true or myth?
Read each claim and pick an answer: the card flips to show the verdict and why. Not sure? Use “Just reveal”.
Card № 01True or myth?
Low fitness is linked to as much extra risk of death as smoking.
True
Low fitness is linked to as much extra risk of death as smoking.
In Mandsager 2018 (122,007 treadmill tests) being in the lowest fitness group carried a risk comparable to smoking, diabetes or heart disease.
Card № 02True or myth?
After age 60 your VO2 max can't go up any more.
Myth
After age 60 your VO2 max can't go up any more.
Trials in people in their 60s, 70s and even 80s show VO2 max rises with training. Older adults gain a smaller absolute amount, but it matters more for staying independent.
Card № 03True or myth?
Every 1-MET (3.5 mL/kg/min) gain in fitness is linked to roughly 13% lower risk of death.
True
Every 1-MET (3.5 mL/kg/min) gain in fitness is linked to roughly 13% lower risk of death.
That is the pooled result of Kodama 2009, a meta-analysis of 33 studies and about 103,000 people.
Card № 04True or myth?
Losing weight raises your VO2 max.
Partly true
Losing weight raises your VO2 max.
The number is measured per kilogram, so losing fat lifts it on paper. Your heart and lungs only actually get stronger with training.
Card № 05True or myth?
Your smartwatch gives you an exact VO2 max.
Myth
Your smartwatch gives you an exact VO2 max.
Watches estimate it from heart rate and pace and can be several points off. Treat it as a trend line, not a lab result.
Card № 06True or myth?
Short hard intervals like 4×4 minutes raise VO2 max more than the same work done at an easy steady pace.
True
Short hard intervals like 4×4 minutes raise VO2 max more than the same work done at an easy steady pace.
Helgerud 2007 found about a 7% rise after 8 weeks of 4×4 intervals; moderate steady running at matched work barely moved it.
Card № 07True or myth?
In most healthy people, the heart's pumping power is the main limit on VO2 max.
True
In most healthy people, the heart's pumping power is the main limit on VO2 max.
Lungs, blood and muscle all play a part, but the amount of blood the heart can push out per beat usually sets the ceiling.
Card № 08True or myth?
VO2 max is mostly genetic.
Partly true
VO2 max is mostly genetic.
Family studies (HERITAGE) suggest about half the variation comes from genes. But almost everyone improves when they train.
Card № 09True or myth?
Only elite athletes get a big health benefit from fitness.
Myth
Only elite athletes get a big health benefit from fitness.
The biggest drop in risk comes from moving out of the least-fit group into below average or average.
Card № 10True or myth?
Without training, VO2 max falls by about 10% each decade after 30.
True
Without training, VO2 max falls by about 10% each decade after 30.
The decline speeds up after 70. Training slows it and can set you back years on the curve.
Nothing here yet. Try another filter.
10
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 ↗
- Tari et al. (Generation 100) (2025). Prog Cardiovasc Dis. 1,565 adults aged 70 to 77, 5 years. Source ↗
- Weeldreyer et al. (2025). Br J Sports Med. 20 studies, about 399,000 adults. Source ↗
- Díaz-Goñi et al. (2026). Nat Ment Health. 27 studies, about 4 million adults. Source ↗