COROS watches use optical wrist-based heart rate sensors to track daily and workout heart rate data. There might be a few seconds delay when viewing your real-time heart rate data on the watch due to data processing. COROS algorithms are carefully calibrated to ensure the best accuracy under most circumstances including underwater. However, the optical wrist-based heart rate sensor may not work properly over tattoos.
There are many factors that can affect heart rate data accuracy. These factors include wrist temperature, tightness of the watchband, excessive sweat/water, watch location on the wrist, tattoo, skin color and hair, blood vessel size, etc. In addition, the heart rate reading results from optical wrist-based heart rate sensors may vary on an individual basis.
Heart rate chest straps usually provide better accuracy than wrist-based heart rate solutions. If heart rate accuracy is important to your training, it is recommended to pair your COROS watch with an ANT+ or Bluetooth heart rate chest strap.
If you have trouble with getting accurate heart rate readings on your COROS watch, please increase the wrist temperature, tighten the watch band, remove excessive sweat/water and relocate the watch on your wrist. If you still can’t receive a good reading, please submit feedback on the COROS app → Profile page → Contact Support → write down details about the issue and “Submit”.