This is a great question, but it pertains not only to body builders but to any woman who has a low BMI and therefore little if any “coverage” for her breast implants.  The main concern is animation of the breast and the only way to avoid this is with implants over the muscle.  This, in turn, can lead to rippling of the implants.
For these reasons, and many others, I use Sientra’s natural feeling, gummy bear, shaped breast implants for breast augmentation in women similar to you.  Very simply, they have the lowest capsule contracture rate of any implant on the market as well as the lowest amount of rippling.
You can also have these implants with a 24 hour rapid recovery so that you can be back in the gym very quickly.