Are you by any chance using cycling HR zones for running?
Since you said you have a Fenix, I would recommend doing a doing a threshold test and changing your heart rate zones to be based on threshold. It will automatically update them as you get fitter. Best to do this with a chest strap to be as accurate as possible.
Since you said you have a Fenix, I would recommend doing a doing a threshold test and changing your heart rate zones to be based on threshold. It will automatically update them as you get fitter. Best to do this with a chest strap to be as accurate as possible.