Your TomTom Touch has a built-in heart rate sensor to help you train more efficiently.
How the sensor works
Your heartbeat is measured by using light to measure changes in your blood flow. This is done on the top of your wrist by shining light through the skin onto the capillaries just below the skin and detecting the changing light reflections.
The performance of the heart rate sensor is not affected by your body fat percentage or body hair. It IS however affected by the position of the TomTom Touch on your wrist, your skin color, skin type, and by whether you have warmed up or not.
Using the heart rate sensor
To get the best performance from the heart rate sensor, see Wearing your Fitness Tracker. Continuous heart rate tracking is switched ON by default.