- VO2max — your body's maximum rate of oxygen use — is a top-tier predictor of longevity, and the American Heart Association has called fitness a clinical vital sign.
- In a meta-analysis, each 1-MET higher fitness was associated with roughly 13% lower all-cause mortality.
- Low fitness can carry a mortality risk comparable to or greater than smoking, hypertension, or diabetes.
- VO2max is highly trainable — a mix of Zone 2 base work and some higher-intensity intervals raises it at any age.
Your doctor measures your blood pressure at every visit. They check your cholesterol, your blood sugar, maybe your weight. But there is one number — arguably a better predictor of how long you will live than any of those — that almost no one measures: your cardiorespiratory fitness, often expressed as VO2max.
What VO2max is
VO2max is the maximum rate at which your body can take in and use oxygen during hard exercise. Think of it as the size of your aerobic engine. It reflects how well your heart pumps, your lungs deliver oxygen, your blood carries it, and your muscles' mitochondria burn it. A higher VO2max means a bigger, more capable engine — one that makes daily life easier and, it turns out, longer.
Why it deserves "vital sign" status
This is not a niche fitness-tracker metric; it is serious cardiology. In 2016, the American Heart Association issued a scientific statement making the case for cardiorespiratory fitness as a clinical vital sign, noting that low fitness is a potentially stronger predictor of mortality than established risk factors like smoking, hypertension, high cholesterol, and diabetes — and that adding fitness to those factors improves risk prediction.
The numbers behind that statement are striking. A meta-analysis of over 100,000 people found that each 1-MET higher level of fitness (roughly one notch of aerobic capacity) was associated with about 13% lower all-cause mortality and 15% lower cardiovascular risk. A later study of adults undergoing treadmill testing found the benefit of higher fitness extended without a clear ceiling — even elite fitness kept lowering mortality. Few interventions in medicine show that kind of dose-response.
The good news: it's trainable
Here is why this matters practically rather than fatalistically: unlike your age or your genes, VO2max responds to training at any age. You are not stuck with the engine you have. The most effective approach pairs two ingredients:
- A large aerobic base. Easy, conversational-pace "Zone 2" work — walking, cycling, hiking — for a few hours a week builds the mitochondrial and cardiovascular foundation. Most people skip this in favor of the occasional brutal workout.
- A smaller dose of intensity. Some higher-intensity interval training pushes the ceiling up, improving the heart's maximum output.
Consistency over months beats heroics. A sedentary person who starts moving sees some of the largest gains of all — the benefit curve is steepest at the bottom.
How to measure and track it
You do not need a lab to start, though a formal treadmill or bike test with gas analysis is the gold standard and worth doing if you can. Many smartwatches now estimate VO2max from your heart rate and pace — imperfect in absolute terms, but useful for watching your own trend rise as you train. Even a simple repeatable field test, like timing a set distance, reflects changes in fitness.
The takeaway
If fitness predicts survival as well as or better than the risk factors we obsess over, it deserves the same attention — a number you know, track, and work to improve. It is the rare vital sign you have almost complete power over. Measure it, then spend the next months making it bigger. Your future independence is, quite literally, riding on it.
In practice: why this matters
We routinely measure blood pressure and cholesterol but almost never measure fitness — despite fitness predicting mortality as well as or better than either. Treating cardiorespiratory fitness as a genuine vital sign, as major cardiology bodies now urge, could reshape prevention: it identifies risk early, motivates the single most protective behavior, and tracks improvement in real time. Few changes to routine care would do more good.
Frequently asked questions
How do I find out my VO2max?
A formal test on a treadmill or bike with gas analysis is most accurate, and many sports-medicine or performance labs offer it. Many smartwatches now estimate VO2max from heart rate and pace — less precise, but useful for tracking your trend. Even a simple field test (like how fast you can walk or run a set distance) reflects it.
How do I actually raise my VO2max?
Build a large aerobic base with easy, conversational-pace 'Zone 2' training, then add a smaller amount of higher-intensity interval work. The combination improves both the plumbing (heart and vessels) and the engine (mitochondria). Consistency over months matters more than any single hard session — and it improves at every age.
References
- Ross R, Blair SN, et al. Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign (AHA Scientific Statement). Circulation. 2016;134(24):e653–e699. doi:10.1161/CIR.0000000000000461
- Kodama S, Saito K, 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;301(19):2024–2035. doi:10.1001/jama.2009.681
- Mandsager K, Harb S, et al. Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing. JAMA Network Open. 2018;1(6):e183605. doi:10.1001/jamanetworkopen.2018.3605
Peer-reviewed sources located via PubMed and cited for education. Citations reflect published research at time of writing.
Dr. Andrew Simon, ND, BCB
Licensed naturopathic physician and board-certified biofeedback practitioner in Seattle. Clinic Director of Rebel Med NW, adjunct clinical faculty at Bastyr University, six-time Seattle Met Top Doctor, and the naturopathic advisor to Washington State on Long COVID. Read full bio →
This article is for educational purposes and is not a substitute for individualized medical care. Talk with a qualified clinician about your specific situation.