'I just read that women shouldn't wear a bra when they rebound. Is that true- that it actually helps promote sagging breasts? That not wearing a bra actually cuts your chances of Breast Cancer'
Largely contingent upon the size of the breasts. If your breasts are full, wearing an athletic bra would still allow for enough movement of the breasts to do some good. As long as there is some 'give' when you rebound. By no means do you have to go braless if it would compromise comfortability or cause pain.