Imagine two people of the same age climbing four flights of stairs.

One reaches the top comfortably, while the other is breathing heavily and needs a moment to recover.

Why does this happen?

There could be several reasons, but one important factor is cardiorespiratory fitness — how well your heart, lungs and muscles work together during physical activity.

And one way to measure this fitness is through something called VO₂ max.

What Exactly Is VO₂ Max?

Every time you walk, climb stairs, cycle or exercise, your body needs oxygen to produce energy.

Your lungs bring oxygen into your body, your heart pumps oxygen-rich blood, and your muscles use that oxygen to keep you moving.

VO₂ max measures the maximum amount of oxygen your body can use during intense exercise.

Think of it as an indicator of your body's aerobic capacity.

Generally, a higher VO₂ max means you have a greater ability to perform activities that require sustained effort.

But here's something important: VO₂ max isn't just for runners or professional athletes. It can provide useful information about everyday fitness too.

Why Should You Care About VO₂ Max?

Most people judge their fitness by how they look or what the weighing scale shows.

But appearance doesn't necessarily tell us much about cardiovascular fitness.

You could have a healthy body weight and still have relatively poor endurance.

The Connection Between Fitness and Long-Term Health

Research involving millions of observations has consistently found that people with higher cardiorespiratory fitness tend to have a lower risk of cardiovascular disease and premature death.

A major 2024 scientific review found that each additional MET of cardiorespiratory fitness — a standard measure of exercise capacity — was associated with an approximately 11–17% lower relative risk of death from any cause in the relevant population studies.

This doesn't mean improving your VO₂ max guarantees a particular health outcome. It simply shows how strongly cardiovascular fitness is associated with long-term health.

And the encouraging part?

You don't need to become an athlete to improve your fitness.

Your Smartwatch Has a VO₂ Max Score. Is That Enough?

Many smartwatches now display a VO₂ max estimate.

It's a useful feature, but there's something worth understanding.

Your watch doesn't directly measure how much oxygen your body consumes. Instead, it uses information such as heart rate, movement and exercise performance to estimate your aerobic fitness.

These estimates can offer a general indication, but they may be inaccurate for individuals.

Smartwatch Estimates vs Laboratory Testing

A laboratory-based exercise test takes a different approach.

During a VO₂ assessment, you exercise on a treadmill or cycle while wearing a specialised mask that measures the oxygen you consume and the carbon dioxide you produce.

Depending on the test, the results can help identify:

• Your current aerobic fitness level.

• How your heart rate responds as exercise becomes harder.

• Exercise intensities that may be appropriate for improving endurance.

• Changes in fitness when testing is repeated under comparable conditions.

The result may be reported as VO₂ max or VO₂peak, depending on what the test establishes.

The real value isn't simply getting a number. It's understanding what that number means for you.

Can You Actually Improve Your VO₂ Max?

Yes. Regular aerobic training can improve VO₂ max for many people.

Walking briskly, cycling, swimming and jogging are all useful ways to begin.

You don't have to push yourself to exhaustion every day.

In fact, both moderate-intensity exercise and appropriately planned high-intensity intervals can improve aerobic fitness.

Why Your Training Should Suit You

The important questions are: How fit are you currently? How much exercise can you tolerate? And how should your training progress?

Two people can follow the same workout and experience different results.

That's why a program that works for someone else may not be the most suitable one for you.

So, Where Should You Start?

If your goal is to improve cardiovascular fitness, begin with exercise you can perform consistently.

Increase your activity gradually, include appropriate recovery, and pay attention to whether everyday activities or workouts become easier.

For general health, adults are encouraged to work towards 150–300 minutes of moderate aerobic activity each week, alongside strength training on at least two days.

But if you're unsure about your current fitness or how intensely you should exercise, a professional assessment and consultation can help you make more informed decisions.