I am curious about whether to change your heart rate zones based on the altitude you are exercising at. For a bit of context, I live ~5,000ft, and can nose breathe up to ~140bpm there. Recently, I went on a run while on a work trip to 1,700ft, and could easily nose breathe into the 150-155bpm range, and had a 0% Pa:Hr with an average heart rate of almost 150bpm, so definitely within my aerobic capacity.
Is this much of a difference in heart rate at different altitudes expected? If so should I use the nose breathing heart rate at all altitudes as my AeT? Or should I use a specific value at all altitudes? I am also curious if I should then lower my AeT significantly when I do hikes/runs at 10,000ft+ in altitude?