73• Do not talk, yawn, or breathe deeply whiletaking heart rate measurements. Doing somay cause your heart rate to be recordedinaccurately.• Because the heart rate sensor uses light toapproximate heart rate, its accuracy mayvary due to physical factors that affect lightabsorption and reflection, such as bloodcirculation/blood pressure, skin condition andlocation and concentration of blood vessels. Inaddition, if your heart rate is extremely high orlow, measurements may be inaccurate.• Users with thin wrists may receive inaccurateheart rate measurements when the deviceis loose, causing the light to be reflectedunevenly. If heart rate measurement is notworking properly, adjust the position of thedevice’s heart rate sensor to the right, left, up,or down on your wrist, or turn the device so theheart rate sensor sits firmly against the insideof your wrist. If the heart rate sensor is dirty,wipe the sensor and try again. Obstructionsbetween the device’s strap and your wrist,such as body hair, dirt, or other objects mayprevent the light from reflecting evenly. Pleasemake sure you remove such obstructionsbefore use.• If your device becomes hot to the touch,remove it until it cools. Exposing skin to a hotsurface of the device for a long time may causeskin burn.