Interesting -- as a data point of one, I'm a New England skier and trail runner. Deep cold doesn't bother me, neither does the summer heat. In the depths of w

Interesting -- as a data point of one, I'm a New England skier and trail runner. Deep cold doesn't bother me, neither does the summer heat. In the depths of winter I ski every weekend in Northern NH, often in 0F, sometimes in -20F weather. I trail run and XC ski all winter in 0-15F temps. Never noticed any breathing issues. In the summer, I run in 95F heat -- you acclimate with the seasons. I have a million years or more of evolutionary engineering in me. I think this is what I am built for.