I had to laugh when I saw this thread....I just went through this! I have been running (I run about 50 miles a week) with regular sports bras you can buy at walmart. I was always wondering why my breasts were so sore. Well, I bought one of those expensive "high impact" sports bras and suddenly realized why my breasts were always sore! They did not have the support they needed for running lol. I am a 40D so I should have known better!
But I do agree, it is amazing when you find a good bra and you feel like you have a new body again!