When doing a breast augmentation, there are usually two areas into which we place the implant – sub-glandular (below the gland) or sub-pectoral or (below the muscle). Some surgeons employ one or the other technique exclusively where as I will decide based on the type of implant, the patients desires and their anatomy. But what happens to the pectoral muscle In a sub-pectoral (sub-muscular plane)? Muscle tissue has low tolerance to mechanical compression. Sub-muscular breast augmentation resulted in a significant reduction in muscle strength adduction. There also was a significant reduction in muscle volume. In a study of 20 patients, the patients involved did not complain due to loss of volume or weakening with adduction. There was no loss with abduction ( moving the arm away from the body).