Submuscular or subglandular Breast Implants for a small-chested rock climber?

Thank you for the question and pictures.
There are pros and cons to the placement of breast implants and the “sub muscular” position versus the "sub glandular position”.    I will try to outline some of the differences here;  you may find the attached link helpful as well.
I think it is in the best interests of most patients seeking breast augmentation surgery to have implants placed in the “dual plane” or sub muscular position.  This positioning allows for more complete coverage of the breast implants leading to generally more natural feel/look  of the implants in the long-term. This position will also decrease the potential for rippling and/or palpability  of the implants (which may increase with time, weight loss, and/or post-pregnancy changes).

The submuscular positioning  also tends to interfere with mammography less so than breast implants in the sub glandular position. The incidence of breast implant encapsulation (capsular  contraction)  is also decreased with implants placed in the sub muscular position.
On the other hand,  sub glandular breast implant positioning does not have the potential downside of “animation deformity” (movement/ distortion of the breast implants  seen with flexion of the  pectoralis major muscle)  they can be seen with breast implants placed in the sub muscular position.   
Everything considered, the vast majority of patients in my practice (including athletes) undergo breast augmentation surgery with breast implants placed in the sub muscular ( dual plane) position.
Best wishes.

Choosing a breast implant placement is very important. In general, I use a subfascial placement. Placing the implant beneath the muscle can often give an unnatural dynamic appearance. By that I mean when the pectoralis muscle flexes (as it does dramatically in rock climbing and other chest dependent exercises) the implant can often be displaced laterally. This is because the implant is really in a dual plane meaning the lateral portion of the implant is generally not covered by muscle in the submuscular implant. One of the detractions from placing an implant in the smaller breasted woman in the subglandular position is that it can show too much roundness at the top of the implant. Placing the implant in a subfascial position helps prevent this. The fascia is the lining of the muscle, much as the gristle that you would see in a piece of meat. It is a stiff lining and minimizes the show at the top of the implant. Rippling is possible with any implant especially in a smaller breasted woman. Saline implants will always have a higher chance of rippling than the cohesive gel silicone implants. Rippling is most common in the lateral portion of the breast and this plane is the same in all placement of implants for breast augmentation. Of course, these are only generalizations and your individual decision must be made in consultation with a well qualified plastic surgeon.