Does a Sub-Muscular placement cause more upper implant firmness vs a sub-glandular placement for athletic women?

I currenlty have 425cc Motiva Ergonomix implants in a sub-muscular placement. There are very firm on the top part of the implant, have very little natural movement. I am curious if a sub-glandular placement would reduce firmness, as the implants would not have the compression and restriction of the pectoral muscles. I have been weight lifting for over 20yrs, and have substantial pectoral musculature. I would like the implants to not only look natural, but to feel natural and move naturally. It seems the sub-muscular placement impacts the softness and movement. Is this correct? Would a sub-glandular placement reduce firmness and constriction, allowing for more natural feel and movement of the implant?