I use this bra for running, and I am very happy with it. I am a 34C, and the Small is very snug, but comfortable. I have not tried to convert this to a racerback (I use the Champion seamless camisole bra when I need a racerback). I like the thicker fabric - you could wear this on its own as an exercise top (I recommend the purple and pink colors if you want to do that).

I never have any chafing problems with this bra. It does not move around at all, and the fabric is soft on the skin. The wide elastic band provides lift and support underneath the breast, and the cups give each breast definition (no uniboob). The straps have never fallen off my shoulders. Overall, I recommend this bra highly for high impact sports.