What Is VO2 Max, and Why Does It Matter?
- Jul 13
- 3 min read
You may have heard the term VO2 max pop up in training, on social media, or on your smartwatch. But what does VO2 max actually mean, and why are so many people trying to track and improve their VO2 max?
What is VO2 max?
Let’s break down the name: V refers to volume, and O2 refers to oxygen. VO2, by definition, is the rate at which your body consumes oxygen for energy, typically measured in L/min (absolute) or mL/kg/min (normalized for body weight). That’s VO2. VO2 max, the key metric, is the maximum rate at which your body can consume oxygen, AKA burn fuel.
Why is VO2 max important?
Essentially, your VO2 max is your engine’s horsepower; it directly determines your maximum capacity for exercise. It’s especially important in evaluating your potential for endurance exercise like marathon running or cycling. The exciting part: you aren’t stuck with the number you have. VO2 max can be increased through training.
Knowing your VO2 max lets you compare where you stand in cardiorespiratory fitness against population averages and gives you an objective benchmark from which to improve. This number also helps you determine your optimal training ranges so that you can make the most of your training time.
It can be helpful to test your VO2max at the start of a new training cycle or season, at monthly intervals throughout your training block, or a few times a year to monitor your overall cardiorespiratory health.
VO2 max and longevity
Beyond exercise, VO2 max is a key marker of cardiovascular health and longevity. It is considered the gold standard assessment of cardiorespiratory fitness, which is a strong predictor of prognosis and survival in those with cardiovascular disease risk factors and cardiovascular disease [1].
Furthermore, VO2 max is considered a modifiable indicator of long-term mortality. In a study of 122 007 patients, cardiorespiratory fitness, quantified through VO2 max testing, was inversely associated with all-cause mortality [2]. Extremely high VO2max (≥2 standard deviations above the mean for age and sex) was associated with the greatest survival. On the other hand, the study found the mortality risk associated with a low VO2max was comparable to traditional risk factors such as smoking or coronary artery disease.
This study is part of a growing conversation around VO2 max and longevity, a striking reminder that we can meaningfully impact our health outcomes and life expectancy through exercise. Tracking your VO2 max allows you to get quantitative data on where you stand and the progress you’re making.
How is VO2 max measured?
After learning about the benefits of knowing your VO2 max, you may be wondering how to get yours. Traditionally, VO2 max testing is done as part of a cardiopulmonary exercise test (CPET) in a lab. Guided by a kinesiologist, you perform an exercise test on a treadmill or stationary bike, increasing the intensity progressively until you reach exhaustion. Throughout the test, you wear a mask that covers your face and connects to a metabolic cart that measures oxygen consumption and carbon dioxide production through a technique called indirect calorimetry. To monitor your cardiovascular system during this maximal exercise test, you may also wear a 12-lead electrocardiogram, blood pressure cuff, and pulse oximeter.
While lab testing is the best validated way to get your VO2 max, it can be difficult to access: it’s primarily offered through clinical infrastructure, and it can be time-consuming and costly.
Why smartwatch VO2 max estimates aren't the same thing
Many people rely on wearables, like a smartwatch or ring, to provide an estimate of their VO2 max. However, wearables typically use algorithms to predict VO2 max based on factors like heart rate response to various activities and population statistics. This is a very different method from lab testing, which requires you to perform maximal exercise and measures gas exchange directly to calculate VO2 max. In a 2024 study, it was demonstrated that a leading smartwatch overestimated VO2 max in individuals with poor fitness levels, while underestimating VO2 max in individuals with high fitness levels [3]. In other words, the people who would benefit most from precise tracking—those at the extremes of the fitness spectrum—are exactly where consumer wearables are least reliable.
With AeroCardia, we are bringing the lab directly to your hands with a portable device that performs indirect calorimetry and provides cardiovascular monitoring, allowing you to test your VO2max, not just estimate it.
Want lab-grade VO2max data without the lab? Sign up to be an AeroCardia beta user here.
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