Samsung Gear S3 classic User Manual page 52

For more information on proper wear and use, see
samsung.com/us/heartratesensor.
If you feel discomfort while using the device, stop using
it and remove it from your wrist. If your device becomes
hot to the touch, please remove it until it cools.
To measure your heart rate more accurately with the
Gear, wear the Gear firmly around your lower arm just
above the wrist.
Applications
Wear the Gear Correctly
Wear the Gear firmly around your lower arm just above
your wrist as shown below. Do not fasten the Gear too
tightly.
43
Heart rate
sensor
S Health