VO2 max: what it is, how to interpret it and when it's really useful

VO2 max: what it is, how to interpret it and when it's really useful

If you use a sports watch, a running app, or any training platform, you've likely come across the metric VO2 max. You’ve probably wondered two things:

1. exactly what it means
2. whether it truly matters for training better

The short answer is this: it can be useful, but only if you understand what it’s telling you and don’t turn the figure into an obsession.

What is VO2 max

VO2 max is the maximum amount of oxygen your body can uptake, transport and utilise during intense effort. It’s usually expressed in millilitres of oxygen per kilogram of body weight per minute.

Put simply:

• the better you use oxygen
• the more work you can sustain
• the better your foundation for endurance efforts

This doesn’t mean someone with a higher VO2 max will always perform better in any sport. It means they have an important part of the “engine” well developed.

Why it matters

VO2 max is relevant because it relates to:

• aerobic performance
• cardiorespiratory capacity
• tolerance for sustained effort
• potential improvement in running, cycling and hybrid sports

For someone who runs, does HIIT or prepares for mixed events like HYROX, it can be a useful metric. For someone who just wants to move some weights 3 times a week, it probably weighs less in decision-making.

How it’s measured

The most accurate way to measure VO2 max is a laboratory treadmill or bike test analysing respiratory gases.

That’s the most reliable method. Everything else is an estimate.

What watches and apps do

Wearables usually estimate it using a mix of signals such as:

• pace or speed
• heart rate
• training history
• recovery

Therefore:

• it can help you track trends
• but you shouldn’t treat it as an absolute truth

If a watch gives you a number, use it as a reference for progress rather than a personal label.

How to interpret it without obsessing

1. Look at the trend, not the isolated number

A one-point change up or down doesn’t necessarily mean much. What matters is the direction over weeks or months.

2. Compare it with your actual performance

If your estimated VO2 max rises but:

• your pace doesn’t improve
• you get just as fatigued
• your recovery worsens

then that number alone isn’t telling the whole story.

3. Consider the context

VO2 max can be affected by:

• heat
• accumulated fatigue
• sleep
• stress
• hydration
• changes in body weight

Workouts that help improve it

Aerobic base

Yes, easy work still matters. If all your training is intense, you’ll lack the base to assimilate more volume and recover well.

Well-planned intervals

This is where sessions like:

• short repeats
• mid-length intervals
• blocks of high-intensity work

come in.

If you’re interested in this part, check out our article on HIFT vs HIIT.

Sustained paces

Tempo and threshold work also helps improve your ability to maintain high efforts without faltering. You can lean on our guide to running pace.

Strength

Although VO2 max is more associated with cardio, improving strength also helps you run better, maintain technique, and use less energy per unit of work.

The role of Zone 2

Zone 2 has become very popular, but it doesn’t work magic on its own. Its usefulness lies in that it:

• improves your aerobic base
• allows you to accumulate work with little fatigue
• helps you recover between hard sessions

The mistake is thinking everything should revolve around that zone. To improve VO2 max, you usually need a combination of:

• easy work
• specific work
• strength
• consistency

When you should pay attention to it

VO2 max deserves more attention if you:

• run regularly
• do endurance events
• prepare for HYROX or other hybrid events
• want to follow a more measurable progression

If you also train by heart rate, you can better calculate your zones with our heart rate calculator.

When not to obsess over it

No need to be constantly checking VO2 max if you:

• are just starting out
• your priority is simply building habit
• your main goal is strength training
• you’re not sleeping, eating or recovering well yet

In those cases, you’ll get more benefit from:

• training regularly
• improving your calorie deficit if you want to lose fat
• organising your weeks better with the AI app
• relying on a community that helps you stay consistent

Practical summary

Do:

• look at the trend
• cross-reference the data with your real performance
• use it as a clue, not a verdict

Don’t:

• obsess over every small change
• compare yourself without context to other people
• forget progress also depends on strength, technique, rest and adherence

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If you train running, do intense sessions or want to better understand your metrics, join our fitness Discord or use the CLIPIN AI app to add more context to your progress.