[QUOTE=IntelSoldier]
My chest certainly hurts during the 2-mile run in an Army PT test. I was told to get rid of the pain by breathing out forcefully and emptying my lungs entirely. The rationale is clear; it’s to really stretch out the tired muscles, like stretching out a cramp. It helps a little, but only for a few seconds.
The belly breathing is something I’ve been told my whole life by just about every teacher of a physical activity. Not only is the diaphragm utilized more, it also pulls air deeper down in the lungs, where better (?) gas exchange takes place.
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I hoped I wouldn’t have to get all detailed. I’ve studied this a lot. That doesn’t mean I know everything about it, but I have quite a basket of information.
Okay, first, here’s a great ribcage animation from Harvard, showing how the volume rises and falls as your ribs do.
http://athome.harvard.edu/programs/hse/video/hse2_9.html
Your lungs aren’t just two oddly shaped balloons. The air passages branch out to thousands of tiny chambers, like two huge bunches of grapes. Each little round airbag is surrounded by tiny blood vessels. The skin between air and blood allows the exchange of gases. The blood lets go of carbon dioxide as it takes in oxygen. The deeper you breathe, and the more completely you empty the lungs, the more little air bags (alveoli) get to participate. Shallow breathing people have hundreds of air bags with the same stale air for hours at a time. Some bags even fill up with liquid.
It seems counter-intuitive, but fast breathing is not the most efficient way to breathe. The gas exchange is not that quick. When you exhale, you breathe out most of the oxygen that you breathed in. The greatest gas exchange happens when you have the greatest number of air bags inflated. During exhaling and inhaling, some air bags are collapsed (and not working.) So, if you can fight off the urge to exhale immediately, gas exchange increases. Wait a step or two before exhaling.
If you are a sprinter, everything is different. In the 10 to 14 seconds of your dash, the oxygen content in your blood won’t change much. Top sprinters don’t breathe at all during the race. Every bit of muscular work must be concentrated on the race, and it can’t be wasted in breathing. You can gasp when it’s over.
So, let’s review. To exhale completely, roll your shoulders forward, drop the front of your ribcage down, and use your belly muscles to force your liver, heart, etc. up into your chest. You can’t get all the air out, unless you are fatally crushed.
To inhale all you can, use the diaphram to push your guts back down as far as you can, pull your ribcage up, and roll your shoulders back. If you can, hold that pose for a step or two before puffing it all out.
One more thing. If you hold your breath by closing your throat, and let pressure build up in the lungs, efficiency goes way down. That’s why some people get dizzy while straining on the toilet.