The diaphragm is not an obscure muscle, but a central, totally essential muscle. The focus of this inquiry is the relationship of the diaphragm to the pelvic floor. The diaphragm moves in concert with the 16 muscles of the pelvic floor; like a piston moving up and down in unison. Thus the muscle which gives us oxygen, existing between the heart and lungs above and the liver, stomach, and intestines below, influences the tone of our pelvic floor and affects both elimination and reproduction.
How we breathe, the health of our diaphragm, affects how we connect to and tone our pelvic floor muscles. The dance of the diaphragm is that as the diaphragm lifts, relaxing, on an exhalation, the pelvic floor also lifts, but it lifts via a contraction. Similarly when we inhale we contract the diaphragm, pressing it down, and the pelvic floor also moves down passively, a release of the pelvic floor muscles.
As the top and bottom of our abdominal cylinder move, the abdominal or core muscles also are engaged. As we inhale, the transversus abdominis, multifidi, and pelvic floor release and broaden, and with the exhalation they all three contract; their activation is in sync with the pelvic floor muscles.
Thus we have a muscular barrel with the respiratory diaphragm above, the pelvic floor below, the abdominal muscles in the front and sides and the tails of the respiratory diaphragm connecting into the quadratus lumborum and psoas in the posterior.
Your breath is a powerful pathway into your pelvic floor, and abdominal cavity! The breath is far grosser than the subtle movement of the pelvic floor; practice toning your respiratory diaphragm and your powerful core muscles, you will feel your pelvic floor catch the ripples and benefit tremendously.