dude, I'm just kidding. I have been running for longer then I have been biking, and I have found that my nipples get sore from chafing. For one thing, ditch the cotton, if you are wearing it. when it gets soaked from your sweat, it gets scratchy. plus, try using some vaseline on those babies when ou go riding. this sort of "lubes" them up so that they don't get chafed.