The polar m400 gps with heart rate monitor adds heart rate monitoring and training capabilities to all the features of the polar m400 gps set heart rate limits in three different ways choose the intensity of your workout depending on heart rate zones and select goals to hit if you leave the zone an alarm will warn you the gps tracks your workout performance and has a back to start function so you wont get lost performance can be analysed in detail on the watch and using the polar flow we