I want to look closely at the relationship between our diaphragm and our pelvic floor. The diaphragm is the ceiling of our pelvis and abdomen, while our pelvic floor is just that...the floor of our pelvis and abdomen. Both of these structures are muscular tissue, both can descend down to a bowl shape, and both can draw up to a flattened, tighter position. Our diaphragm descends down to draw in every breath, taking up room in our abdominal and pelvic cavity. When our diaphragm takes up more space, we accommodate by expanding our lower rib cage and chest, and our pelvic floor descends ever so slightly with every breath. These are all components of the natural rhythm of our breathing pattern and pressure displacement.
If our lower rib expansion and chest expansion are not functioning when we take in air, then the increased pressure in the abdominal/pelvic cavity has to find somewhere to go, and often puts increased pressure on our pelvic floor. Let me give some examples. If we If we hold our breath while exerting, our diaphragm works against our pelvic floor. The dome shaped diaphragm expands down as we take a breath in and hold it. Its attachment to our lower rib cage also prevents our mobile lower ribs from expanding when we brace with breath holding. All of these components, including a descended diaphragm that takes up more room in our abdominal cavity and the inability of our lower ribs to expand, means the pressure is going to go directly to our pelvic floor.
In another example, if every time we push, reach, or brace our abdomen, we puff our belly out, we are activating our rectus abdominus and oblique muscles which will hold our lower rib cage down, preventing it from expanding. Again, if our ribs aren't able to expand, the pressure will have only one place to go and that is down. Eventually our poor pelvic floor becomes a punching bag and with time may give way, allowing pressure to force through the openings in our pelvic floor, i.e. incontinence.
Now that we have a mental picture of the struggles our poor pelvic floor faces everyday, take comfort in knowing that we can re-train our bodies to stabilize in the optimal way. This includes breaking ourselves of our breath holding habit. Breathing out as you exert will lift your diaphragm, allowing the pressure to displace your lower rib cage. It also means consciously thinking about firing our pelvic floor and transversus abdominus before exerting. A good way to coach yourself through this is to watch your belly as it should draw in and not puff out. If you feel increased downward pressure on your pelvic floor while lifting something heavy, pushing a lawn mower, or even yelling at a soccer game, chances are you are activating your rectus abdominus and obliques instead of your transversus abdominus. This would mean that you would see your belly expand versus draw in.
Give yourself some time to work on your breathing pattern, it is tough and often requires outside coaching. Feel your lower ribs and chest expand with every breath, and take care to notice if you breath hold when getting in/out of your car, lift the laundry basket, or get off of the couch. Focus on breathing out in these situations as you re-train yourself to displace that pressure upwards. If you don't feel you can get this breathing rhythm down, I recommend you consult with a local physical therapist or yoga instructor to get further guidance.