What is the low ambient temperature when shirtless running becomes unadvisable? I find that whenever I run in a shirt for, say, 1:20, I get problems like chafed nipples. So, for now, I run without a shirt. But the weather is getting colder.
It's inadvisable. Dress properly instead. Get yourself a decent running top. E.g. search rei-outlet.com for brands like hind, insport, sporthill, sugoi, pearl izumi.
I'd highly recommend the sporthill infuzion splice top, for example.
