Are You Ignoring Your VO₂ Max?

Let’s stop lying to ourselves. Our mirror selfies don’t prove we’re in shape. Neither does our ability to finish a half-marathon in “under two hours” (especially when my Strava says I walked the last three kilometres).

You can own the fanciest smartwatch in the store, wear matching gym sets, and post your morning smoothie to Instagram — and still have the cardiovascular capacity of a houseplant. In other words, you’re basically just hot girl fit.

Because the real metric — the one that decides if you can actually move your body efficiently for more than a few minutes without collapsing — is your VO₂ max. And unless you’ve been actually reading up about it, you don’t know it.

That’s fine. But here’s the uncomfortable truth: you should. Because VO₂ max isn’t just about fitness. According to a large-scale study published in JAMA Network Open in 2018, higher VO₂ max is one of the strongest predictors of long-term survival — even more so than smoking status, blood pressure, or cholesterol. The American Heart Association has gone as far as to call cardiorespiratory fitness a “clinical vital sign,” meaning it should be monitored as routinely as heart rate or blood pressure.

So yes, it’s about how long you’re going to stay healthy enough to enjoy your life.

What the Hell Is It?

VO₂ max — maximal oxygen uptake — is the maximum amount of oxygen your body can use during intense exercise. Measured in millilitres per kilogram per minute, it’s basically your body’s engine capacity. Higher number = bigger engine. Lower number = pray your building has a lift.

It’s not about how much air you can suck in — it’s about how efficiently your heart and lungs can deliver that oxygen to your muscles, and how well those muscles can use it. That’s why elite endurance athletes obsess over it.  In fact, a 2020 review in the European Heart Journal found that VO₂ max levels in the top third of the population were associated with up to a 45% lower risk of premature death compared to the lowest third. It’s also been shown to be a better predictor of longevity than BMI or resting heart rate.

If your VO₂ max is high, you’ll run faster, recover quicker, and probably live longer. If it’s low, you’ll be winded carrying laundry upstairs and probably will have a shorter life span.

How to Find Your Number

Unfortunately, the most accurate way to find out is in a lab. You run or cycle while a technician keeps making it harder, all while you breathe into a sealed mask that measures every molecule of oxygen in and CO₂ out. It lasts 10–20 minutes, ends in near-misery, and spits out the number.

However, cheaper options exist. A Garmin or your Apple watch will estimate it using heart rate and pace. Or you can do the “one-mile walk test” — walk as fast as you can, check your heart rate at the finish, plug it into an online calculator. These won’t be lab-accurate, but they’ll give you a baseline.

The Bad News About Age

VO₂ max declines about 10% per decade after your twenties. If you’re leading a sedentary lifestyle, it’s worse. But the slide isn’t inevitable. Train for it, and you can slow the drop to a crawl — even reverse it for a while. The biggest controllable factor is activity level. Move more, and your body gets better at using oxygen. Stop moving, and it doesn’t.

How to Jack It Up Without Quitting Your Job

Forget endless “fat-burning zone” cardio. If you want results fast, you need high-intensity interval training (HIIT).  A 2013 meta-analysis in the British Journal of Sports Medicine found HIIT to be significantly more effective than steady-state cardio for improving VO₂ max across all fitness levels. We’re talking short bursts of work at 80–90% of your max heart rate, followed by rest. Three to five minutes on, same off, repeat. It’s deeply unpleasant and wildly effective.

If you’re starting from zero, even brisk walking will help. But the magic happens when you mix it up: hills, sprints, swimming, rowing, circuits. Your body adapts to whatever stress you throw at it — so keep changing the stress. Oh, and because VO₂ max is relative to body weight, shedding excess fat without losing muscle will improve your score before you even get fitter.

Learn to Breathe Like You Mean It

Most people breathe like amateurs. Improving VO₂ max isn’t about inhaling more — it’s about using what you inhale better. That means slowing your breath, engaging your diaphragm, and, yes, breathing through your nose when you can. Train it in low-intensity sessions so it’s automatic when you’re pushing hard.

You can fake a personal best. You can Photoshop your waistline. You can even bluff your way through a 10K by “accidentally forgetting” to stop your watch at red lights. But you can’t fake VO₂ max.

This number isn’t vanity. It’s the difference between being the 65-year-old who still hikes mountains and the one who gets winded opening a jar. It's also the difference between living long and living well.