Until recently, it was thought that a weak pelvic floor is one that literally allows things to fall through the pelvis. You may still come across this view, which is rooted in now-outdated anatomical thinking that lacked an appreciation of biotensegrity. In a pre-biotensegrity world, the body was seen as a stack of components; bones stacked one on top of the other with gravity pulling down. In this world, if anything falls it needed pushing up via the tightening of muscles. The modern view is different.