Today in fascinating but not green: A pressing health Q I asked my sis about. I know you too’ve always wanted a full explanation of this:
Me
Hey Yo. Another body related question: You know how one breathes through one’s lungs? And the lungs I believe are well above one’s gut. So then why is it that if I breathe in deeply, I can make my tummy puff out too? Is air really going into that area?
Sis
When you breath you only breathe into your lungs, and the pressure difference between the outside world and your chest cavity is what sucks the air in. The diaphragm separates your chest cavity from your abdominal cavity. When you poof out your stomach, the diaphragm gets sucked down to keep the volume (and pressure, since they are inversely proportional) in the abdominal cavity the same. This then means your chest cavity is bigger, which means the pressure goes down, which means air rushes in to equalize with the outside, and you inhale.
What was always confusing to me is that when you “suck in” your stomach, you’re inhaling too. I finally learned in med school that when you do that, your posture changes (shrug the shoulders up) to increase the chest cavity up/outwards. This sucks air in, and also sucks the diaphragm up (and hence, belly in).
It takes much less energy to bring down the diaphragm than to increase the other parts of the chest cavity (ex: raising shoulders), so it’s the most efficient way to breathe. This is why, at rest, people breathe with their bellies, but after exercising (when diaphragm can’t do enough), they also breath with their shoulders. When people are in true respiratory distress, their “accessory muscles of respiration” in the front of the neck will try to help out too, and this is a bad sign.
I wonder if all doctors get random Qs like these from their siblings. The lesson here: Don’t breathe with your accessory muscles of respiration –
If you think about it we all use our accessory muscles to breath at times. Think about when you are running, doing an aerobic activity or if you run quickly up a couple flights of stairs. When you stop, the tendency is for people to bend forward to put their hands on their knees to “catch their breath”. This anchors our accessory muscles and allows us to breath more deeply to relieve the shortness of breath.
(people with COPD and emphysema do the same thing… although without the workout part)
A good tip to protect your lower back, is to learn how to “suck in” your stomach muscles without holding your breath. You can protect your back while squatting down or lifting. This way you are contracting your abdominal muscles, not using your diaphragm, and your back can maintain proper positioning.
Comment by Steve Balogh — July 17, 2007 @ 6:58 pm