Samsung Gear S2 classic User Manual page 81

Applications
Tracking your heart rate
The Gear can automatically measure and track your heart rate. Your Gear measures your heart rate at regular intervals.
This feature may not function properly while you are moving.
To activate or deactivate this feature, tap S Health on the Apps screen, and then rotate the bezel right and open the settings screen,
X
Options > Auto HR and select a frequency level.
tap
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