Heart Rate Zones Don't Match Between Profile and Actual Run

aalxmbc Registered Users Posts: 1
New Seeker
edited January 24 in TomTom Sports
My max heart rate is 175 bpm so the heart rate zones come out as 158 (peak), 140 (perform), 122 (cardio), 105 (fat burn) & 88 (easy) but when I run and look at the data, it shows the transition between easy to fat burn is at 118 bpm, from fat burn to cardio is at 135 bpm, from cardio to perform is at 154 bpm, and from perform to peak is at 173 bpm. Why is their this discrepancy?