It takes me a day or two at high altitude. I was on the heart unit back in May with Blood Pressure problems (236/11; they now have me on 2 types of Blood pressure/ heart meds. It's easy to get the dizzys and suck wind on the first day (above 9000 '). The Back gets to me also, but I can shut that out and lose track of time; focus (nice thing about fly fishing). I still like to go at it hard.
Take it easy (the age is catching up with us lol) !!!
Alpinefly