Polar wrist based heart rate monitors are highly useful in helping us assess our day to day physical activity. This is highly beneficial for the modern human being who lacks the time to be able to assess the physical activities. This device helps us plan our daily lifestyle accordingly and stay fit. Various polar devices are available with wrist based heart rate measurement. These devices use the technology of optical heart rate monitoring (OHR). This technology has been seen in hospitals for quite some time now. This technique works by optically detecting the blood flow through the skin present on the wrist.
A bright green light is present on the back of the polar device. This bright green light shines through the skin on your wrist. A photodiode present on the device is used to detect the amount of green light that reflects back from the skin. Every time the heart beats, blood is pumped through the veins. A stronger flow of blood through the veins is noticed when the green light reflecting back and detected by the photodiode is less. Between one heart beat and other the volume of blood flow in veins is lesser and hence more green light will be reflected and detected by the photodiode. Using these variations in the green light reflected from the skin and detected by the photodiode, the polar heart rate monitor determines your heart rate.
However, high sensitivity is exhibited by the optical heart rate monitoring process towards motion. Movement is capable of interfering with the light route of the LED light towards the detector thereby messing up the correct reading or measurement of the monitor. In order to filter out any distortions that could be caused by the movement, two sensors are used by the polar heart rate monitor devices that work with wrist-based form. In these two sensors, one sensor detects the movements of the hand while another sensor is used to measure the heart rate. The data obtained from the sensor tracking movement is then run through an algorithm which combines the data from both sensors thereby giving an accurate reading.