Just went on an 18 mile run with this bra and it did a great job. I did chafe a little bit under one arm but I think it was from the shirt I was wearing. I give it four stars because it wasn't THAT supportive and I'm an A cup. I think if you had a bigger chest it wouldn't really be that supportive. Overall it's super comfortable and very breathable. Didn't chafe near as much as with any other bra I've had.