Traveling to higher elevations? While my home is at nearly sea level, I am currently at 5400’. I noticed an increase in my resting heart rate (via my Fitbit) the first four days I was here, so was curious if altitude affected heart rate. (It adjusted to normal rather quickly, probably because I go walking each morning.). It does...and much more. Read this:
I had to work at 10,500 feet on top of a plateau for a year once. Initially I became fatigued and winded very quickly but I got used to it. When I eventually finished I went on holiday to London and I was on a high for three days from the extra oxygen at sea level. Considering I was in my late 20's I had a ball. Apparently when you are in a rarefied atmosphere for a while your body produces extra haemoglobin or blood oxygen carriers.
I don't know about heartrate. I do recall being very sensitive to the effects of alcohol after moving from sea level to 6000'. That sensitivity did improve while there. Athletes are known to claim there is a difference in their performance for the first day or so. Now you've got me curious....