Possible to Get Under Muscle Breast Implants Without Cutting Muscle?

For the implants to sit properly, you need to divide the lower border of the pectoralis muscle. If you do not, the implants will sit too high.

As the other consultants have outlined, in development of the subpectoral, submuscular or dual plane pocket, most surgeons will release, divide or cut the muscle's attachments to the breast bone to ensure that the implant settles on the front of your chest wall and does not "lateralize" when you press your hands on your hips. 

I would agree that even in the most athletic patients, this surgical manuever does not compromise their ability to exercise, post-op.  Apart from the obvious recruitment of additional soft tissue (muscle) over the implant, which masquerades wrinkling and rippling, the dual plane is preferred because of the lower rate of capsular contracture and improved mammographic surveillance.