Apple introduced a setting that allows users to save power during certain workouts like walking and running. When this setting is turned on, the optical sensor on your Apple Watch remains turned off during the activity. This results in you seeing the workout in Cardiogram but no heart rate measurement during that time.
To fix this, we have to change the Power Saving setting on your Apple Watch.
- On your watch, go to the settings app.
- Tap on “Workout” near the bottom of the settings list.
- Slide the slider to the off position to turn off “Power Saving.”
New workouts should now record your heartbeats during the activity.