Cardio Fitness: What Apple’s new health metric means and how you can use it

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Low Cardio Fitness Notifications are about your lungs as well as your heart
Low Cardio Fitness notifications are about your lungs as well as your heart.
Photo illustration: Graham Bower/Cult of Mac

Apple’s VOmax metric measures the performance of your heart and lungs when you push yourself to the limit. Up until now, though, it’s only been useful to serious fitness fanatics. No wonder Apple buried it in the Health app, where most users never found it.

But watchOS 7.2 and iOS 14.3, which Apple released Monday, change all that. In those updates, the VOmax metric has been renamed Cardio Fitness. Now it can detect lower ranges and send alerts when the reading gets too low. That makes it the latest in a series of potentially life-saving health notifications from Apple Watch.

Here’s everything you need to know to get the benefit of this essential new feature.