The heart rate does not track properly on downhills while running. It seems to be tied into the accelarometers and always give me very high heart rates despite not working hard. I have used the TomTomCardio Runner (first version) and never had a problem other than sweat and cold. I am frustrated with the reliability to track my heart rate because it throws off my training stress scores and average heart rate readings. Are there workarounds? Is there a problem with the algorithm for the sensor from LifeQ? I have done a factory reset, updated the software, and even sent one watch back and am on a second. They both did the same thing.