Working out and building your pectoral muscles does not lift breast implants in my experience. Most implants are now placed in a dual plane position, meaning that the upper 70% or so of the implant is under the muscle, and the lower 30% or so of the implant is over the muscle. For the implant to move upwards, the tissues at the lowest portion of the implant would have to thicken and push upwards. For most women, there is little to no muscle in this location, and this is why little upward movement of the implant occurs with muscle building. Most women find that their implants move outwards more than up with pectoral muscle contraction.
Hope this helps!
Dr. Bresnick