Fitness is full of numbers meant to help you become faster and stronger. There’s your mile run time, your resting heart rate and measures of strength and flexibility. But perhaps the gold standard is VO2 max.
A handful of years ago, the test — which tracks how much oxygen your body absorbs — was an obscure tool mainly used by elite athletes. Today, it’s touted by fitness professionals and wellness experts like Peter Attia as being a useful measure for all exercisers.
But getting an accurate number requires an expensive and exhausting lab evaluation. And estimates provided by wearable devices might not tell you much. So how useful is it to invest time and money in the full work-up, and how important is knowing your VO2 max?
For everyday people who want to be healthy and live a long time, the measurement is “the best piece of empirical information we have on health and longevity,” said Kate Baird, a clinical exercise physiologist and the coordinator of running and metabolic services at Hospital for Special Surgery in New York.
The key, she said, is acting on what the data tells you.
What is VO2 Max?
“VO2 max” is a two-digit number that expresses how effectively your body metabolizes oxygen. The measurement itself is the milliliters of oxygen consumed in a minute per kilogram of body weight.
As you exercise, your body needs ever more oxygen. The more you can efficiently consume, the more energy your muscles will have, increasing the time and intensity you can exercise. Generally speaking, someone with a higher VO2 max will be able to sustain a run or an aerobic activity at a given pace longer than someone with a lower VO2 max.
The test has participants exercise to exhaustion to measure that threshold, essentially measuring the size of someone’s internal aerobic engine.
Most VO2 max tests are conducted with a medical professional in a lab, with a specialized mask that measures the amounts of oxygen and carbon dioxide that are inhaled and exhaled. Participants then work out with the goal of reaching maximal aerobic capacity, or the point of complete exhaustion.
The same score might be considered high for one person and low for another, depending on their genetics, sex, age and body composition.
The test is difficult, which can be a turnoff for those who don’t want to push to their limits, and it costs a few hundred dollars, which is generally not covered by insurance.
What does it tell you about longevity and performance?
Studies have shown that a higher score is a strong predictor of longer life span.
Your VO2 max can decline by about 10 percent per decade starting at around 25, but it is possible to increase or maintain it with activity. A 2021 study of 2,000 middle-aged men and women found that small amounts of activity could improve VO2 max. The more effort you put in, the higher the benefit; moderate to vigorous physical activity increased that number even more dramatically.
Testing your VO2 max annually can show you whether you are slowing that decline, Ms. Baird said. For serious athletes, proper rest and sustenance are also key for maintaining or improving your score. Measuring VO2 max before and after a few months of focused training can reveal if you are working out too hard or if you are fueling properly during your workouts, among other things, according to Luke Greenberg, a physical therapist and co-founder of MotivNY, a physical therapy and training studio.
What about VO2 max on wearables?
Not everyone can afford to spend their time and a few hundred dollars on a lab-based test. As a result, dozens of wearables have recently entered the market claiming to measure VO2 max with algorithms that use heart rate and GPS data to extrapolate the value.
Some worry that those estimates may not be accurate, but it’s difficult to assess their accuracy because the algorithms are not published, according to Dimitris Spathis, a researcher at the University of Cambridge.
In 2022, Dr. Spathis coauthored a study in which researchers developed a model to better predict VO2 max using data from 11,000 participants. He’s hopeful that most athletes will someday be able rely on wearables instead of paying for tests.
If you don’t have the time or interest to take a lab test or use a wearable device, Ms. Baird advises finding other ways of setting goals to increase your fitness. There’s a good chance that a VO2 max test would tell you information that you already know.
“The best predictor of performance is your performance,” she said. If you enjoy running, set a time or distance goal. If you are more sedentary and aiming to exercise more, start moving in a way that feels tolerable and safe, starting with a walk of as little as 10 to 15 minutes.
And above all, be patient.
“Every single person is going to respond differently to training based on their genes and other lifestyle factors,” Ms. Baird said. “It can take years to move your body in the direction you want to go.”
