This is an excellent question, what happens to the pectoral muscle after breast augmentation
What was done at the initial surgery will determine what happens after the surgery. If large implants were placed, the muscle is often separated from the breast bone (sternum), in order to produce more cleavage. Those fibers will never reattach, even if they are sewn back on with heavy sutures. When the pectoral muscle is used, the muscle can "jump"; it is contracting but doesn't know that it has been disconnected from the sternum. The more the muscle is detached, the more the motion artifact will occur.
Often, especially when large implants are used, the muscle atrophies, or becomes thinner. However the nerve supply remains intact.
Patients should consider the destructive effect on the pectoral muscle before having large implants.
