Factors like wearing the device too loosely, swinging your arms, or sliding of the device over your skin can impact heart rate readings. In addition, wearing the device too tightly, raising your arms, or clenching your fists can affect blood circulation, which also affects sensor performance. When testing your heart rate, it is recommended that you keep your arm straight, remain static, and relax your muscles. Ensure that the device remains in close contact with your skin.
Note: Even when you wear the device correctly, individual differences such as skin color, body hair, tattoos, and scars can also affect heart rate sensor performance slightly.