What is VO2 Max?

Amy Brownstein, MS, RDN - Registered Dietitian Nutritionist

VO2 max measures how well your body uses oxygen during exercise. Learn how to measure it, what it says about your health, and how to improve it.

VO2 max: What it is

VO2 max measures how well your body uses oxygen during exercise. It represents the maximum amount of oxygen your body can take in, deliver to organs and muscles, and use during all-out exercise. A higher VO2 max means your heart and lungs deliver more blood to your muscles and your muscles use that oxygen more efficiently.

The “V” stands for volume, the “O” for oxygen, and the “max” for maximum. VO2 max is reported as milliliters of oxygen per kilogram of body weight per minute (mL/kg/min). VO2 max varies based on age, sex, and fitness level. Fitness is the factor you can change to influence your VO2 max.

How can you measure VO2 max?

There are a few ways to measure VO2 max, and accuracy varies by each tool.

Lab testing: The gold standard for measuring VO2 max. In lab testing, you wear a mask attached to a metabolic cart while you run on a treadmill or pedal on a stationary bike. Exercise intensity increases until you can’t go anymore. At the same time, the metabolic cart measures how much oxygen you breathe in and how much carbon dioxide you exhale.
Field tests: Time walks or runs estimate VO2 max based on your time, heart rate, age, and weight. They’re less precise, but are more accessible and easier to use.
Wearables: Smartwatches and heart rate monitors help estimate VO2 max based on heart rate data. Accuracy varies with wearables, with VO2 max calculated at rest off by about 2 mL/kg/min and VO2 max derived from exercise data varying by 10 mL/kg/min. Despite this variation, wearables can still help you notice trends in VO2 max.

What does VO2 max say about your health?

VO2 max is often used to assess longevity. Research suggests that a higher VO2 max is associated with a lower risk of all-cause or cardiovascular-related deaths. One large analysis found that a higher VO2 max, indicative of greater fitness, is associated with half the risk of early death compared with low fitness.

How to improve your VO2 max

You can’t change your age or sex, but you can modify your activity level, which can influence VO2 max.

Start with steady cardio. If you’re new to exercise, brisk walking may be enough to raise your VO2 max. Otherwise, make sure you’re regularly incorporating aerobic exercise into your routine.
Incorporate intervals. High-intensity interval training (HIIT) alternates hard efforts with easy recovery. Research suggests that HIIT and continuous endurance training improve VO2 max in healthy adults, with HIIT producing somewhat larger gains. Try one or two interval sessions a week, such as exercising 3 minutes hard followed by 3 minutes easy, repeated four times.
Continue progressing. As you become more accustomed to exercise, gradually add more activity to your routine, whether it’s increasing exercise duration or incline or trying a new activity. This helps your body keep adapting.