Female body builders in general have little body fat and the process can also melt away breast tissue. Refilling the breast skin envelope is then challenging in this situation because there is so too little fat or breast tissue to cover the edges of a breast implant placed on top of the muscle. So saline implants above the muscle are out of the question. Implants placed under the muscle are even more problematic because the pressures or forces applied to them during weight lifting can rupture the implant or more commonly shift them out of position. I saw one patient who while bench pressing squeezed her implant out of position so it formed an unsightly U-shape around the lower border of the pectoralis major chest muscle.
The only answer although not optimal is a cohesive gel breast implant placed on top of the chest muscle and in selective cases the addition of acellular dermal matrix to ensure the edges of the implant and rippling are not visible, although that is costly and is not the right choice for all such patients.