What Is VO2 Max?

Reviewed by SOMA HEALTH's Medical Research Team

VO2 max is the maximum amount of oxygen your body can take in and use during intense exercise. It is one of the most studied measures of aerobic fitness, and higher values track with better health outcomes across large populations. This guide explains what it captures, why researchers care about it, and how the mitochondrial side of fitness fits in.

A quick note: this page is educational and structure/function in nature. VO2 max is a fitness measure, not a diagnosis, and nothing here is intended to diagnose, treat, cure, or prevent disease. If you have a heart or lung condition or symptoms during exercise, talk with your doctor before making changes.

What VO2 max measures

VO2 max, sometimes written as maximal oxygen uptake, is the ceiling on how much oxygen your body can deliver to and consume in working muscle during all-out effort. It is usually expressed in milliliters of oxygen per kilogram of body weight per minute (ml/kg/min), which lets you compare people of different sizes. The higher the number, the more oxygen your system can move and use, and the more sustained aerobic work you can perform.

The measure reflects a chain of steps working together: your lungs oxygenating blood, your heart pumping that blood, your blood vessels delivering it, and finally your muscle mitochondria extracting the oxygen to produce energy. VO2 max is a whole-system number. A limitation anywhere along that chain, from cardiac output to mitochondrial density, can cap it.

How it is measured

The gold-standard test is a graded exercise test in a lab, on a treadmill or cycle ergometer, while a mask captures the oxygen you consume and the carbon dioxide you produce. Intensity rises until oxygen uptake plateaus despite harder effort. Because that test requires equipment, many people rely on estimates instead, from submaximal fitness tests, field tests, or the algorithms in wearable devices. Wearable estimates are convenient for tracking trends over time but are less precise than a lab measurement, so treat the exact figure with some caution.

Why VO2 max is treated as a longevity marker

Beyond athletic performance, VO2 max has drawn attention because cardiorespiratory fitness is one of the strongest population-level predictors of long-term health. Large cohort studies with decades of follow-up have found that higher midlife cardiorespiratory fitness is associated with lower long-term mortality risk, and reviews describe VO2 max as a key predictor of longevity at the population level. It is worth being precise about what that means: these are associations across groups, showing that fitter populations tend to fare better over time. They describe a marker of health, not a treatment, and no supplement or single number guarantees an outcome for any individual.

The plausible reasons are intuitive. A higher VO2 max generally reflects a stronger, more efficient cardiovascular system and greater metabolic capacity, both of which relate to how the body handles stress, activity, and daily demands. That is why clinicians increasingly view fitness as a vital sign worth paying attention to.

What VO2 max depends on, and how it changes

Age, sex, genetics, and training

VO2 max tends to peak in early adulthood and decline gradually with age, and average values differ by sex, largely because of differences in body composition, hemoglobin, and heart size. Genetics set part of your baseline and part of how much you respond to training. But the modifiable piece is large: regular aerobic training can meaningfully raise VO2 max at essentially any age, and inactivity lowers it.

The two levers: delivery and extraction

Improving VO2 max means improving either oxygen delivery or oxygen extraction. Delivery improves as endurance training increases blood volume, stroke volume, and capillary density. Extraction improves as muscle builds more and better mitochondria, raising its capacity to use the oxygen that arrives. The most effective training combines steady aerobic base work with higher-intensity intervals, which strongly stimulate both sides.

The mitochondrial connection

The extraction side of VO2 max is fundamentally about mitochondria. Endurance training drives mitochondrial biogenesis, the building of new mitochondria, largely through the PGC-1α signaling pathway, increasing the oxidative capacity of trained muscle. Keeping that network healthy also depends on mitophagy, the recycling of worn-out mitochondria. Our explainers on mitochondrial biogenesis, mitophagy, and mitochondrial health unpack how the build-and-recycle cycle works. Because that cycle underlies aerobic capacity, it is where interest in compounds like urolithin A intersects with fitness.

Where urolithin A fits

Urolithin A is a gut postbiotic made from ellagitannins in pomegranates, walnuts, and berries; not everyone's microbiome produces it efficiently. It is studied mainly for supporting mitophagy, the recycling side of mitochondrial renewal, rather than as something that raises VO2 max directly. It is best thought of as supporting the machinery of muscle energetics, with exercise doing the primary work of building fitness.

The human evidence has focused on muscle and exercise-related outcomes rather than VO2 max as a headline endpoint. Singh and colleagues (2022, Cell Reports Medicine) studied 500 mg and 1,000 mg daily over four months in middle-aged adults and reported effects on muscle strength and aspects of exercise performance. Liu, D'Amico and colleagues (2022, JAMA Network Open) reported improved muscle endurance in older adults. The first-in-human study by Andreux and colleagues (2019, Nature Metabolism) found safety and tolerability up to 1,000 mg per day and a mitochondrial gene-expression signature. A 2025 trial in distance runners has also examined urolithin A in an endurance-trained population. These are structure/function findings; they do not establish that urolithin A raises VO2 max, and human research overall is still emerging per a 2024 systematic review in Ageing Research Reviews.

The preclinical basis is broader but earlier-stage: Ryu and colleagues (2016, Nature Medicine) showed urolithin A induced mitophagy and improved muscle measures in rodents, with lifespan extension in C. elegans. Useful as motivation for the human trials, but not proof of benefit in people. For the full breakdown, see our clinical studies summary and urolithin A for energy.

How to raise your VO2 max

The practical playbook is well established. Build an aerobic base with regular steady sessions, then add higher-intensity interval work, which is especially effective at pushing the ceiling upward. Be consistent over months rather than chasing quick changes, and allow recovery so adaptations can consolidate. Support training with sleep, adequate protein, and a diet that includes the polyphenol-rich foods behind urolithin A production, covered in our page on foods high in urolithin A. If you are considering a supplement as one input, our urolithin A guide and best urolithin A gummies roundup explain what to look for.

Honest limitations

A few caveats keep this in perspective. VO2 max is a marker associated with population health, not a personal guarantee, and the association is strongest across groups rather than for predicting any one person's future. Wearable estimates drift from lab values. And urolithin A has not been shown to increase VO2 max; its human evidence centers on muscle and mitochondrial markers, is still emerging, and reflects structure/function support rather than treatment. If you have symptoms during exercise or an underlying heart or lung condition, see your doctor before increasing intensity.

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This guide is educational and is not a substitute for advice from a qualified healthcare provider.