If your watch is loosely worn or is not well-attached to your wrist, it will not be able to obtain data through the fluctuations of your blood flow. In this case, check that your watch is on your wrist properly and that the watch face is facing upwards. It is recommended that you wear it slightly above your wrist joint for maximum comfort. Check that your watch is attached correctly to your wrist while you are exercising to prevent it from slipping.
Ensure that the back of your watch is clean, dry, and free of obstruction from foreign objects. Excessive sweating during exercise can cause your watch to slip or obstruct light reflecting off the skin that is used for the measurement, resulting in inaccurate data. In this case, remove your watch and wipe off any sweat or smudges, then reattach it to your wrist.
Ensure that the back of the watch is clear of foreign objects that may block the heart rate monitoring sensor.
Extreme low temperatures may also alter the blood flow of the human body and cause the heart rate measurement to be inaccurate. In this case, it is recommended that you initiate a heart rate measurement once you have warmed up.
Heart rates are much easier to measure during regular movement exercises (such as running, walking, and riding) compared to irregular movement exercises (such as basketball and free activities), while wrist strength exercises (such as weightlifting) may even complicate the process.
If you find that your heart rate is abnormal during an exercise, keep your watch facing upwards and stand still for approximately 10 to 15 seconds to check whether your heart rate returns to normal. If your heart rate cannot be measured after multiple attempts, it is recommended that you restart your watch and try again.