Do sub-muscular breast implants make your pectorals weaker?

That has not been my experience.  In my practice, patients report that they are able to return to full activity, with full strength over the long-term. Discuss your specific concerns with your chosen plastic surgeon. Best wishes.

Yes, there is some weakness in bench press and push up type exercises following placement of a breast implant under the pectoralis muscle. In most cases the origin of the muscle along the fifth or sixth rib is divided to allow for a smooth contour of the lower pole of the breast. That is why I recommend that women not do exercises that isolate the pectoralis muscle when they have implants placed in the subpectoral pocket. You may be a candidate for subglandular placement if you desire to continue weight lifting/body building.