But most people don't think about breathing a lot. I know I've been breathing for quite a while, and for most of that time I more or less took it for granted. You breathe in, you breathe out.
My son had asthma as a child, and I learned some things I didn't understand well at the time. For instance, why is difficulty breathing out the test for asthma? If the airways are constricted, shouldn't you have trouble breathing in as well?
Then, after many years of running in all weather, I came down with exercise-induced asthma. I wound up on Advair, albuterol, and Singulair. They helped a lot, as did a few other things, like acupuncture, and today I'm not taking any prescription medications. I'm also not running outdoors in cold weather. Cold air is my main, and possibly my only, trigger.
All this got me thinking about breathing, and so I did a little reading. Some of the things I'm about to say may sound simple, but I never did find a source that says, Here's what you need to know about breathing. Things are scattered, and occasionally sources conflict. What I'm putting down here is my best understanding.
There are three main measurements of breathing.
First is respiration rate. In an adult at rest, this is normally in the teens per minute. When you're running, the respiration rate can double or triple.
Second is something called tidal flow. This is the amount of air you take in and send out with each breath. Tidal flow also increases when you're running -- you may have felt your lungs open up after you've been running awhile. That's the tidal flow kicking in.
I can't put a number on this increase, but it is limited by maximum lung volume. Jason R. Karp, in his 2007 doctoral dissertation, Lungs and Legs: Entrainment of Breathing to Locomotion in Highly-Trained Distance Runners, has this to say on page 50:
"When assessing pulmonary characteristics of collegiate distance runners, it has been observed that flow limitation is more prevalent in the upperclassmen compared to the lowerclassmen. ... It is possible that the upperclassmen have learned, through two or three more years of high-level training, to maximize their ventilatory capability."
Unlike these guys, most of us will always have some lung capacity we're not using.
So we have a bucket with more than adequate volume, and we have a highly flexible rate at which we may fill and empty the bucket.
So no worries, right? Well, there's those pesky bronchial tubes. Think of them as a funnel. Take your beaker of air, and pour it into your bucket -- through the funnel. If the funnel is constricted, which is what the term bronchial spasm means, you've got a problem. Actually, you probably have asthma.
Bloody hell, if I may say so from personal experience. The little alveoli down in the lungs, which is where the oxygen transfer from the air to the blood takes place, are waiting patiently, and they're just not getting enough air.
Which brings us to the mystery from my son's childhood -- why is peak flow (the size of the funnel) always measured on expiration, and never on inspiration?
The answer is that expiration is the Achilles' heel of the lungs. The main breathing muscle is the diaphragm, which sits at the bottom of the lungs and is really big and powerful. When it contracts, you breathe in. When it relaxes, you breathe out.
Got that? Breathing out, your basic breathing muscle is relaxing. It's the weak moment, and that's what doctors measure.
There are muscles that work during exhalation. The intercostals are the muscles that sit between your ribs. Some of them work when you're breathing in, some when you're breathing out. Other muscles can also get involved in breathing out, but with one exception they're not a big deal.
The big deal is your abdominal muscles. Properly trained, they can really help you expel air from your lungs.
There's a yoga breathing technique that illustrates this. Start breathing in down at your belly, and run the inspiration progressively up through your ribs to your collar bones. Then reverse. When you get back down to your belly, you'll find your abdominals working really hard.
Please don't do this more than three times in a row. A little bit cleanses the lungs. Overdo, and you may faint. (See Stacie Stukin, "The Anti-Drug for Anxiety," Yoga Journal, April 2003, p. 111. This article also discusses alternate nostril breathing, which is a good way to pass the time while you're waiting at a red light.)
Runners also need to link their legs to their lungs. Breathing is the basic rhythm of your body, and everything you do should flow with that.
For runners, this boils down to a simple question: How many steps per breath? For years I was basically a 2-2 runner -- breathe in for two steps, breathe out for two steps. Recently I've been working on a 3-2 pace. I find it helps me fill my lungs more fully.
An added benefit goes to your knees. Runners hit the ground hardest when they begin to exhale. 2-2 means you always exhale on the same knee. 3-2 switches between knees. (See Bud Coates and Claire Kowalchik, "Running on Air: Breathing Technique," Runner's World, April 2013.)
I still slide into 2-2 when I'm going faster, and on sprints and hills I slip into 1-2. I try to avoid 1-1. Rapid, shallow breathing -- panting, if you will -- reminds me too much of my asthma.
There. That's what I've learned.