Apple has a fitness feature that allows Apple Watch users to track their cardio fitness levels through VO2 max measurements.

Before the release of watchOS 7.2 which arrived at the end of 2020, the Apple Watch could estimate higher levels of VO2 max, but only for outdoor walks, runs, or hikes.

Assuming your smartwatch is running watchOS 7.2 or later, Apple Watch can now determine your cardio fitness as you walk throughout the day though, so you don't need to intensely exercise for it to take and analyse your cardio fitness level.

Apple Watch Series 8-1
Apple Watch Series 8
$329 $399 Save $70

The Apple Watch Series 8 has a great design, heaps of sensors, and more features than you'll probably know what to do with. Its battery life isn't the best on the smartwatch market, but fast charging makes it easy to charge daily and the fitness features are superb.

What is VO2 Max?

VO2 max, or maximal oxygen uptake, is the measurement of the maximum amount of oxygen a person can use during intense exercise. It's basically a measurement used to determine the endurance of a person prior to - or during - the course of training, and it can be improved through physical activity.

Apple notifies Apple Watch users' when their cardio fitness levels are either high, above average, below average, or low (in comparison to other people in their same age/sex group). Before it will do that though, the "Cardio Fitness Level" feature needs to be set up in the Apple Health app on iPhone.

How to setup Cardio Fitness Level on Apple Watch

Here's how to setup the Cardio Fitness Level feature on Apple Watch:

  1. Open the Health app on your iPhone.
  2. Tap the Browse tab in the bottom right corner.
  3. Search for 'Cardio Fitness' in the search bar at the top.
  4. Tap on Cardio Fitness Levels.
  5. Tap on Set Up.
  6. Confirm health data that might affect heart rate.
  7. Tap through to learn about Cardio Fitness.
  8. Tap Turn on Notifications to receive alerts when your cardio fitness level is low.
    • Or, tap Not Now.
  9. Tap Done.

And that's it!

How to set up Cardio Fitness Levels with your Apple Watch and iPhone photo 2

Once setup, the Apple Watch will take cardio fitness measurements whether you're on an outdoor run or a walk, and all the results will be pulled together and viewable inside the Apple Health app.

There are multiple factors that can lower cardio fitness levels, such as pregnancy and lung and heart conditions, but if your cardio fitness levels should dip low, and if notifications are enabled, the Apple Watch will send notifications with recommendations on how to improve it.

Want to know more?

The Apple Watch Series 6, Series 7, Series 8 and Watch Ultra are all capable of monitoring blood oxygen levels too. Read our separate feature on how to get a reading if you have a Watch Series 6 or newer. We also have an Apple Watch tips and tricks feature that will give you details on all the features Apple Watch offers and how you go about finding them and setting them up.