I didn't buy this bra because of working out, etc., but rather because I am frustrated with non-sport bras that don't fit well. This bra is awesome! I am on-line now to purchase additional ones. I find that I am not as conscious about moving about when I am wearing this bra because I know that I am "secure" and the straps don't move, fall, etc. Th bra dries quickly in warm weather. I only wish that the bra was offered in another color besides white.
I work in this bra (personal trainer), and trained in it while on vacation -- nordic walking and cycling. I feel secure enough that I would run in it as well (were that I was still running). For cotton, it is pretty breathable, but I have not yet tried it in extremely warm weather. I am very pleased with its support and comfort. The hook & eye closure makes for easy on/off. (Have you tried to wrestle on or off a pullover on a hot day or after a hard workout??) The absence of underwires is a blessing! I highly recommend this bra.