Hold , and select Settings > Watch Sensors > Wrist Heart Rate.

Status

Enables or disables the wrist heart rate monitor. The default value is Auto, which automatically uses the wrist heart rate monitor unless you pair an external heart rate monitor.

NOTE: Disabling the wrist heart rate monitor also disables the wrist-based pulse oximeter sensor. You can perform a manual reading from the pulse oximeter glance.

During Swim

Enables or disables the wrist heart rate monitor during swimming activities.