Multi-platform compatibility Get accurate heart-rate information without the need for a separate chest strap. Your heart rate is measured through a sensor in the watch that monitors changes in the blood flow in your wrist. This is done by shining light through the skin and detecting the changing light reflections. See real-time running, cycling and swimming information at a glance. Track your distance, time, pace, speed and calories burnt as you train on an extra-large display. Select a zone to match your training goal and always know whether you need to speed up or slow down.Heart rate monitoring is the single most accurate means to understand how your body is responding to exercise.