So as I started reading I was thinking wool, then I read further.

Wool just seems better, specially as I age and metabolism slows. Poly is fine when you're working harder but doesn't seem to retain the heat so well when you stop. They are starting to get a better handle on odor with treated poly, but wool is better there too.

You can't have too many options for wool pieces. Try a Smart Wool T-shirt too. I it like better than Ice Breaker's T.