Muscle animation? Window shading? (Photo)

Windowshading animation is caused by the pulling of the pectoral muscle where it has been detached and then heals into the capsule around the implant. It often occurs with a double bubble type contour over the lower breast, which I do see in the pictures. If you see pulling up along the crease across the bottom of the breast when you flex your pecs, then it is windowshading animation. I usually correct this by converting to the split muscle plane which re-attaches the muscle behind the implant but preserves coverage over the upper part.

It appears you have the early beginnings of an implant that is beginning to "bottom out".  This is a problem with subpectoral implants due to the muscle activity.  Continued exercise would indeed be expected to worsen the problem over time.The solutions are to reinforce the pocket with either a capsulorrhaphy or tissue replacement (acellular dermal matrix) or to convert to subglandular pockets.  The subglandular space (subfascial) removes the activity of the muscle and corrects the animation deformity.  The new textured cohesive gel implants were designed for placement in the subglandular space.