Would pectoral exercise ruin implants and pocket?

Your concerns are realistic and valid. There is no question
that pectoralis exercises after having sub muscular breast implants place can
cause pocket abnormalities. Some Plastic Surgeons tell patients they should
never return to those exercises after augmentation. It is certainly more of a
problem when implants re below the muscle vs above the muscle but don't fool
yourself. Implants above the muscle can also widen the breast pocket over time.
It is less of an issue performing pectoralis work when implants are above the
muscle. So in body builders I recommend above the muscle. In the average
patient who works out a lot it can go either way. Your anatomy may push a
surgeon to choose one pocket vs the other. That decision is made on a case by
case basis.

Most surgeons recommend refraining from upper body exercise for some period of time after augmentation, until the scar capsule forms around the implant. The pectoralis muscle usually covers only the upper an inner part of the implant, and heavy use can push the implants downward and outward. Still, the vast majority of surgeons prefer under the muscle position for implants. Exceptions are made on a case by case basis, particularly for weight lifters and body builders, in whom large muscles are more likely to actually displace the implants.All the best.