The heart rate monitor (HRM) shows your heart rate in BPM (beats per minute) during a workout. To start a workout, you must pair an external HRM device with your watch through the application menu.

The workout starts when the external HRM device (chest belt for instance) starts to send valid data, while being worn.
The workout stops once the external device is removed.

In the activity chart, you can select the HRM workout (heart icon) and see the details. The graph shows the HRM values during the workout, using 4 colors representing 4 different heart rate zones.

The different heart rate zones are displayed using your estimated maximum heart rate in BPM (beats per minute). Your maximum heart rate (HR max) is calculated with the common formula of 220 minus your age.

Red: Maximum Zone

More than 85% of your maximum HR (Heart Rate).
This is the highest intensity zone. It develops maximum performance and speed.
For trained and fit people only.

Orange: Cardio Zone

Between 70% and 85% of your maximum HR (Heart Rate).
This is the medium-to-high intensity zone.
It improves performance and cardio capacity.

Yellow: Fat Burn Zone

Between 50% and 70% of your maximum HR (Heart Rate).
This is the low-to-medium intensity zone.
It improves basic endurance and fat burning. Recommended for longer workouts.

Green: Rest Zone
Under 50% of your maximum HR (Heart Rate).
In this intensity zone, you might be walking and moving but your heart rate is low and you are not exercising.