When comparing my zone 2 heart rate in my Garmin device to my Z2 HR in intervals, there is a drastic difference. I am wondering which is more trustworthy? Max Z2 HR in Garmin is listed as 112 - 130 and intervals lists my Z2 from 134 - 148. I think about the very unscientific method of “If you can talk in single sentences at a time, you are in z2”, which is definitely above 130bpm for me. I am also older (42) and don’t want to overdo my endurance rides.