Experts Say VO2 Max Is the Most Important Health Metric—But Just How Do You Improve It?

VO2 max is among the most elusive terms in fitness. You may have heard of it, as it’s often heralded as the number that defines your cardiovascular fitness. Yet for many, the concept is confusing and misunderstood—a pinnacle of athletic prowess for elite endurance athletes, sure, but not for average folks without access to a performance lab. Well, this metric is still important for those of us who are just hitting the gym, going for runs, or trying out a new fitness class from time to time.

“VO2 max affects your ability to sustain exercise,” says Dr. Brent Marshall, sports medicine program director at the University of Western States. Want to cycle faster without feeling winded? Finish a round of boxing without getting gassed? Or keep up when you challenge a D1 track star to a foot race? “For runners or swimmers or cyclists or anyone working on their cardiorespiratory fitness, [improving VO2max] can help them have longer and more productive workouts,” he says.

But it’s not just about your fitness; it’s also a really good predictor of overall cardiovascular health. Improving your VO2 max has daily benefits even away from the sport, says Donna Cennamano, manager of training at Cyclebar and personal trainer and certified breath coach. “It promotes a sense of calm and increased awareness. When you improve your aerobic capacity, you have greater mental alertness, increased energy, and more stamina.” And who couldn’t use a little more of all of that?

So What Actually Is It?

Ever wondered what fuels your body during a long run, brisk hike, or any activity that you sustain for more than just a few minutes? You’re in what’s called an aerobic state, and oxygen is the predominant fuel source for your muscles. This is different from anaerobic activities, like sprinting or lifting heavy weights for a few reps, where your body relies on other sources, like glucose, for quick bursts of energy.

VO2 max is a measure of your aerobic capacity, or “the amount of oxygen we can consume during physical exercise,” says Cennamano. Basically, the more oxygen that your muscles can use during workouts, the easier it will feel and the longer you can go. But here’s the thing: VO2 max is not just about how much oxygen you can breathe in. It’s all about how efficiently your body can use that oxygen. Your heart and lungs need to be working in sync to deliver this oxygen to your muscles. Naturally, this process becomes harder as you pick up the exercise intensity and your breathing becomes labored. So that threshold just before your body switches over to an anaerobic process—where you have to dig deep to keep going and push through the pain—that’s your VO2 max.

How to Test Your VO2 max

VO2 max is quantified in millimeters of oxygen consumed per minute per kilogram of body weight—the higher the number, the more aerobically fit you are. But it is notoriously hard (and rather expensive) to measure precisely, requiring clinical testing, specialized equipment, and the somewhat daunting task of wearing an oxygen mask as you perform a grueling workout. So, this rigorous protocol has been relegated to the realm of elite athletes who are serious about crunching numbers to improve their performance.

Today, modern fitness trackers, like a Garmin watch, also have VO2 max predictors, and can give you a ballpark figure of your VO2 max. Although, this estimate is based on your heart rate and how fast you’re moving, it is not nearly as accurate as in-lab testing. You can also judge your perceived effort during exercise to gain useful insights into your aerobic capacity. Marshall recommends a basic running or cycling test as a simple yet effective method.

First, choose a pace that challenges you but is sustainable. For beginners, this might mean a brisk walk or light jog that you can maintain for five minutes before your muscles start to burn and legs turn to Jello, he says. The goal here isn’t to push until you drop but to find a steady, challenging pace that you can maintain for a set period. You can track your workout with a fitness tracker or apps like Strava or Nike Run Club to determine your pace and how long you can hold it.

In about a month after training regularly (which we dive into below), you can repeat the same test again under similar conditions. The aim is to see how much longer you can maintain at the same pace. If your muscles gave out at the five-minute mark last time, you might now be able to push through to 12 or 15 minutes. While you won’t have a number to reference, “you can really see those gains in fitness,” says Marshall.

How to Improve Your VO2max

Whether you measure it or not, you can improve your VO2 max. It comes down to two things: high-intensity training and breathing.

According to Marshall, high-intensity interval training (HIIT) is one of the most effective methods for improving VO2max. This is highlighted across research, including a 2023 study that found that interval runs were much more effective than moderate-intensity continuous running to boost VO2 max in soccer players.

During interval training, you perform a short bout of really intense exercise, then rest and repeat. “Essentially, what this does is push your body in and out of the aerobic-anaerobic range,” Marshall explains. “You’re going up to that threshold—maybe a little bit past it.” By oscillating between the two, you challenge your body to adapt to both aerobic and anaerobic demands. We won’t lie—this type of training is very physically demanding: You need to put enough load on your body to get a response. “If you’re not pushing yourself hard enough, you might see some improvement, but it won’t be as efficient as if you’re pushing yourself to the upper end of those ranges,” Marshall says.

For the most effective interval training, aim to perform exercises at about 80 percent of your maximum heart rate during the high-intensity phases, Marshall says. You can estimate your max heart rate with the formula 220 minus your age. And although running is a great method, you can perform any dynamic movement that gets your heart rate up, like jump squats or burpees, instead.

Initially, work within shorter intervals (45 seconds to a minute), but as you progress, you can push your intervals longer to result in even faster improvements to VO2 max. According to a 2013 meta-analysis, the most effective interval length was between three and five minutes.

Remember when I said it isn’t about how much oxygen you consume but how well you use it? Well, efficient breathing plays a critical role in maximizing oxygen uptake and utilization, and it may be the most overlooked factor for improving VO2 max. You don’t need to take in more air to increase your VO2 max, Cennamano says. Instead, you need to slow it down and learn to lighten your breath. This will help improve your carbon dioxide tolerance, which helps deliver more oxygen to your tissues.

But because breathing isn’t instinctual for everyone (myself included), you need to train it. When you’re first developing a breathwork practice, Cennamano recommends doing it separately from exercise to stay intentional and mindful. First, just perform a check-in. Ask yourself how you’re breathing, she says. Are you using your nose or mouth more? When you take a deep breath, are you a vertical breather—bringing it all the way into the stomach—or a horizontal breather—expanding your ribs?

Once you know your tendencies, you can start to incorporate common techniques, including nasal breathing, which was found to be effective for increasing sub-maximal power output in cyclists, and diaphragmatic breathing. Cennamano also recommends the Oxygen Advantage if you want to take a workshop.

After you feel in control of your breath, you can start incorporating it into exercise, like during a walk or light jog. You don’t have to breathe through your nose the whole time, says Cennamano; just focus on it for five to ten minutes of your practice and then start to increase that as you become more comfortable. The goal is to build a foundation that will support you when you ramp up the effort: “You need to build the tolerance so when you are venturing into higher intensity workouts, you’re not over-breathing,” she says.