Your Apple Watch can estimate your cardio fitness level and send you a notification when it’s low.
What is cardio fitness
Cardio fitness is a measurement of your VO2 max, which is the maximum amount of oxygen your body can consume during exercise. Your cardio fitness level is a strong indicator of your overall physical health and a predictor of your long-term health. Your Apple Watch gives you a cardio fitness estimate by measuring how hard your heart is working during an outdoor walk, run, or hike.
Set up Cardio Fitness Levels and turn on notifications
- From the Health app on your iPhone, tap the Summary tab.
- Tap Set Up under Cardio Fitness, then tap Next.
- Confirm your details. Any changes you make here will be saved to your Health Details in Settings.
- Tap Next.
- Follow the onscreen prompts to learn about other factors that can lower your cardio fitness, as well as the cardio fitness levels for your age and sex.
- Tap Next.
- Tap Turn on Notifications to receive a notification if your Apple Watch detects that your cardio fitness level is low. You must be at least 20 years old to turn on notifications.
- Tap Done.
If your cardio fitness levels are low for your age and sex, you’ll receive a notification. If your cardio fitness levels continue to remain low, you’ll receive additional notifications.
Most people can improve their VO2 max by increasing the intensity and frequency of their cardiovascular exercise. Certain conditions or medications that limit your heart rate might cause an overestimation of your VO2 max.
View your cardio fitness data
- Open the Health app on your iPhone, then tap Browse.
- Tap Heart, then tap Cardio Fitness.
- Tap D, W, or Y to view your average for the Day, Week, or Year.
- Tap Show All Cardio Fitness Levels.
- Tap a cardio fitness level to compare your results to other levels based on your age and sex.
You can also tap the “i” icon to view the average cardio fitness levels for all ages for Female, Male, or All.
How Apple Watch estimates your cardio fitness levels
Apple Watch Series 3 or later can record an estimate of your VO2 max using the heart and motion sensors during an outdoor walk, run, or hike. It can also estimate your VO2 max if you start an outdoor walk, run, or hike in the Workout app. Apple Watch supports a VO2 max range of 14-60 mL/kg/min that is validated for users 20 years or older.
To estimate your cardio fitness level, your Apple Watch also takes into account your:
- Medications that might affect your heart rate
It can take at least 24 hours wearing your Apple Watch, followed by several workouts* and passive measurements with your Apple Watch before you receive an initial estimate.
*Push workouts are not supported.