VO2 Max: Why It Predicts Longevity and How to Improve It
10 min read · September 2026 · by Manikanta Sirumalla
Somewhere in your watch app is a number labelled "Cardio Fitness" or "VO2 max" that most people scroll past. It deserves a closer look. Of every measurable thing about your body, this one has the strongest relationship with how long you are likely to live. It is also one of the most improvable. This article covers what it is, what the numbers mean, how much to trust your watch, and exactly how to raise it.
What VO2 max measures
VO2 max is the maximum volume of oxygen your body can consume per minute during exhaustive exercise, expressed relative to body weight in millilitres per kilogram per minute (ml/kg/min). It is measured in a lab with a mask that analyses every breath as you run or cycle to exhaustion.
The number integrates the whole oxygen delivery chain: how much air your lungs move, how much oxygen your blood carries, how much blood your heart pumps per minute, how well your vessels deliver it, and how much of it your muscle mitochondria can actually use. A weakness anywhere in the chain lowers the number. That is why it is such a good summary of fitness, and why it predicts health so well.
For most people, the ceiling is set by cardiac output, the heart's pumping capacity. Elite endurance athletes have hearts that pump nearly twice as much blood per minute as sedentary people.
Why it predicts longevity
The relationship between cardiorespiratory fitness and death has been studied in cohorts of hundreds of thousands of people, and the results are remarkably consistent.
A 2018 study of more than 122,000 patients who underwent treadmill testing at the Cleveland Clinic found that mortality fell steadily as fitness rose, with no upper limit. People in the lowest fitness group had about five times the death rate of the "elite" fitness group over the follow-up period. Going from low fitness to below average was associated with a 50 percent reduction in mortality. And the risk associated with low fitness was greater than that of smoking, diabetes, or coronary artery disease (Mandsager et al. 2018).
A meta-analysis pooling 33 studies found each 1 MET increase in fitness (about 3.5 ml/kg/min) was associated with a 13 percent lower risk of all-cause mortality and 15 percent lower risk of cardiovascular events (Kodama et al. 2009).
Why? Because VO2 max is a measure of physiological reserve. A heart, vascular system and set of mitochondria that can deliver 50 ml/kg/min under maximal stress are systems with headroom to survive illness, surgery and ageing. Fitness is, in effect, a stress test you have already passed.
The American Heart Association has recommended that cardiorespiratory fitness be treated as a clinical vital sign for exactly this reason.
What a good number looks like
VO2 max varies with sex, age, genetics and training. Population reference values, roughly:
| Age | Men: average | Men: top 25% | Women: average | Women: top 25% |
|---|---|---|---|---|
| 20 to 29 | 42 to 46 | 50+ | 35 to 40 | 43+ |
| 30 to 39 | 40 to 43 | 47+ | 33 to 37 | 40+ |
| 40 to 49 | 37 to 40 | 44+ | 30 to 34 | 37+ |
| 50 to 59 | 33 to 37 | 40+ | 27 to 31 | 34+ |
| 60 to 69 | 29 to 33 | 36+ | 24 to 28 | 31+ |
Elite endurance athletes reach 70 to 85 in men and 60 to 75 in women. Values decline roughly 10 percent per decade after 30 in sedentary people, considerably less in those who keep training.
The longevity data suggests the goal is not a specific number but a quartile: being in the top 25 percent for your age and sex is associated with most of the benefit, and being "elite" (top 2.5 percent) with a little more.
How accurate is your watch?
Apple Watch, Garmin and others estimate VO2 max from the relationship between your heart rate and your pace during outdoor walks and runs. A given pace at a lower heart rate implies higher fitness. It is a model, not a measurement.
Validation studies find watch estimates correlate reasonably with lab tests across a population, but the error for an individual can be five or more ml/kg/min in either direction. Apple's estimate is calibrated to a range of about 14 to 65 and tends to underestimate in fit people, because it is built around walking and moderate running. Garmin's tends to overestimate in some users. GPS errors, hills, heat, and running with a stroller all confuse the model.
Two rules make the number useful anyway:
- Trust the trend, not the value. If your estimate rises from 38 to 44 over six months of training, that improvement is almost certainly real, even if the absolute numbers are off.
- Give it good data. Steady outdoor runs or brisk walks on flat ground, with a well-fitted watch, produce the best estimates. Treadmill and indoor sessions do not update it on most devices.
If you want a real number, a lab test at a university exercise physiology department or sports clinic costs a modest amount and takes about 20 minutes.
How to improve it
VO2 max responds to two things: raising the ceiling with high-intensity work, and widening the base with easy volume. Both matter, and the mix depends on where you are starting.
High-intensity intervals. Intervals that push you to 90 to 95 percent of maximum heart rate and hold you there for several minutes are the strongest single stimulus. The classic protocol from Helgerud and colleagues, four intervals of 4 minutes at 90 to 95 percent of max heart rate with 3 minutes of active recovery, improved VO2 max by about 7 percent in eight weeks, significantly more than moderate continuous training or shorter intervals at lower intensity (Helgerud et al. 2007). A meta-analysis of interval studies found improvements of 5 to 15 percent are typical in untrained and moderately trained people, with high-volume long intervals producing the largest gains (Milanović et al. 2015; Bacon et al. 2013).
Practical protocol, once or twice per week:
- Warm up 10 minutes easy.
- 4 x 4 minutes hard (breathing very hard, can say only a word or two), 3 minutes easy between.
- Cool down 5 to 10 minutes.
Alternatives with similar effect: 5 x 3 minutes, 6 x 2 minutes, or hill repeats of 3 to 4 minutes. Very short sprints (30 seconds and under) improve VO2 max less than these longer intervals, because they do not hold cardiac output at its maximum for long enough.
Zone 2 base. Easy aerobic work builds the mitochondria, capillaries and stroke volume that intervals exploit, and in untrained people it raises VO2 max on its own. The typical structure that works is 80 percent of aerobic time easy, 20 percent hard. See Zone 2 Training: The Complete Guide.
Progression. Untrained people improve fast, 10 to 20 percent in three to four months. Trained people improve slowly and have to add volume and intensity carefully. Genetics sets the ceiling; studies of trainability found some people improve by 40 percent and a few barely at all on identical programs, but nearly everyone improves.
Body weight. Because VO2 max is expressed per kilogram, losing fat raises the number without any change in your heart. Real fitness and a better ratio both count toward the longevity benefit.
Age is not the obstacle it seems
Most of the decline in VO2 max with age in sedentary people is from inactivity, not from age itself. Older adults respond to interval and endurance training with relative improvements similar to younger people, and masters athletes in their 60s and 70s routinely post numbers above sedentary 30-year-olds. Starting later still works, and it works quickly. Talk to a doctor first if you have heart disease, and build up over weeks rather than starting with 4 x 4s.
Where lifting fits
Strength training has a small effect on VO2 max, mostly in untrained people. It does not replace aerobic work here. But muscle mass and strength predict longevity independently of cardiorespiratory fitness, and the combination of strength and aerobic fitness produces the lowest mortality risk in cohort studies (Momma et al. 2022). The right answer is both. See Strength Training for Longevity.
The bottom line
VO2 max is your body's oxygen ceiling and the strongest fitness predictor of longevity there is. Aim to be in the top quarter for your age and sex, judge your watch by its trend rather than its value, and train it with one or two sessions a week of 3 to 5 minute hard intervals on a base of easy Zone 2 work. Then add strength training, because the combination beats either alone.
Sources
- Mandsager K, Harb S, Cremer P, et al. "Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing." JAMA Network Open, 2018.
- Kodama S, Saito K, Tanaka S, et al. "Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women: a meta-analysis." JAMA, 2009.
- Ross R, Blair SN, Arena R, et al. "Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign: A Scientific Statement From the American Heart Association." Circulation, 2016.
- Helgerud J, Høydal K, Wang E, et al. "Aerobic high-intensity intervals improve VO2max more than moderate training." Medicine and Science in Sports and Exercise, 2007.
- Milanović Z, Sporiš G, Weston M. "Effectiveness of High-Intensity Interval Training (HIT) and Continuous Endurance Training for VO2max Improvements: A Systematic Review and Meta-Analysis of Controlled Trials." Sports Medicine, 2015.
- Bacon AP, Carter RE, Ogle EA, Joyner MJ. "VO2max trainability and high intensity interval training in humans: a meta-analysis." PLoS One, 2013.
- Momma H, Kawakami R, Honda T, Sawada SS. "Muscle-strengthening activities are associated with lower risk and mortality in major non-communicable diseases: a systematic review and meta-analysis of cohort studies." British Journal of Sports Medicine, 2022.
Frequently asked questions
What is a good VO2 max for my age?
Rough population averages: men in their 20s about 42 to 46, women about 35 to 40; values fall roughly 10 percent per decade. Being in the top quartile for your age and sex is associated with the largest longevity benefit. Endurance athletes reach 70 to 85 (men) and 60 to 75 (women).
How accurate is the Apple Watch VO2 max?
It is an estimate from heart rate and pace during outdoor walks and runs, not a measurement. Validation studies find it tracks lab values in the right direction but can be off by several points for an individual, and it tends to underestimate in fit people. Use it for your own trend over months, not as an absolute number.
How do I improve VO2 max fastest?
High-intensity intervals: for example four intervals of 4 minutes at about 90 to 95 percent of max heart rate with 3 minutes of easy recovery, once or twice per week, on top of easy aerobic work. Untrained people can improve 10 to 20 percent in a few months; trained people improve more slowly.
Can VO2 max improve after 50?
Yes. Older adults respond to the same interval and endurance training as younger ones, in relative terms. VO2 max declines with age, but most of the decline in sedentary people is from inactivity, and training in your 50s, 60s and beyond can restore it to the level of a much younger sedentary person.
Does strength training improve VO2 max?
Only slightly, and mainly in untrained people. VO2 max is driven by cardiac output and the oxidative capacity of muscle, which need sustained elevated heart rate to develop. Lifting builds muscle and strength, which independently predict longevity, so do both.
Why does VO2 max predict longevity?
It integrates the function of the heart, lungs, blood, blood vessels and muscle mitochondria into one number. A high value means every one of those systems works well and has reserve. Low cardiorespiratory fitness is one of the strongest modifiable risk factors for early death identified in cohort studies.
