Let's science the sh*t out of your breathing

Okay, now that some of you may have seen the movie The Martian I'll level with you on the title.  When the buzz was on about the movie, a friend forwarded a clip from director Ridley Scott's storyboard which was a simple cartoon with a sphere representing Mars and the words 'Science the shit out of Mars'. I thought that phrase would make an excellent title for a post I wanted to write here analyzing breathing, of course with the hope that most of you would not see that cartoon and take the title as original, not a copy which it is in reality.  Last week I watched the movie, and to my dismay I saw that Ridley Scott actually used the phrase in the movie also -  Matt Damon (astronaut Mark Watney) who was abandoned by his teammates thinking he was dead collects himself after the initial shock and is determined to survive in the hostile martian environment.  After a quick survey of the situation, he goes 'I'm gonna have to science the shit out this.'  It seems like that phrase is the most popular line in the movie.  Even so, at the risk of being utterly unoriginal, I will still use the line here anyway.   By the way, if you get a chance, do see the movie. Jim Green, who is Director of Planetary Sciences Division was so impressed with the book and the movie that the movie received a lot of NASA 'support' and involvement throughout its production. Jim held a science conference call on The Martian this Tuesday, which I missed because it was during regular working hours. I plan to watch the recording. I must admit, just for the record, that I didn't find everything in the movie palatable. For instance, the atmosphere looked too dense for Mars, and the gravity also looked much stronger, more like Earth's. You can nitpick even more, but in spite of these, I found the movie very enjoyable. Tara was with me and, even as a self proclaimed science hater she thoroughly enjoyed the movie. In fact, she was mad at me, she still is, that we missed the first two minutes where the exact set up of the accident was shown which led to Mark getting separated in a sandstorm and the crew taking him for dead.

Alright, enough of the movie. Let's get back on track and start sciencing the sh*t out of your breathing.

Of all the parameters that signify endurance, probably the single most important one is known as VO2Max. This is just geek speak for the Maximum (Max) Volume (v) of Oxygen (O2) that one can consume in a minute. The higher your VO2Max the higher your capacity for long duration hard work - that is, your endurance.  They use this metric to study physiological response of astronauts to long stays in space to understand how their ability for hard work is affected when put in a weightless state for a long time.  The same metric is used by coaches in various sports, and especially in running.  There can be some variations depending on the situation. For example, a lighter runner can work as efficiently with a smaller VO2Max as a heavier runner who has a higher VO2Max because the heavier runner needs to carry more weight because he has a heavier body.  So in the context of running, usually the metric as it relates to body weight,  VO2Max per kg of body weight, is used. In contrast, in the sport of rowing where the rower doesn't have to carry himself like a runner, it is the absolute volume that matters.  In any case, the amount of oxygen you can intake and transport to your muscles is the key factor in long duration endurance sports where you spend a lot of time working aerobically.  When working aerobically, you continually produce energy by taking in oxygen using your lungs which is then pumped out by your heart through the arteries and transported to the capillaries that reach your muscles. The muscles then use the oxygen to generate energy to do work. In anaerobic work, on the other hand, you are using stored energy in your muscles. Stored energy is limited, but when you have it you can use it for powerful or short duration bursts such as sprints. You won't be able to sprint for a long time because your are withdrawing from stored energy which is limited.

When you train yourself for endurance, your aerobic capacity increases, which is to say your VO2Max goes up so that your capacity to perform long duration work (e.g., long runs) increases. When we run, do we always consume the maximum volume of oxygen? No. Typically, people run at a certain fraction of their VO2Max.  We can run harder or easier by working at a higher or lower fraction of  our VO2Max, but generally at a certain level of effort we are performing at a certain percentage of our VO2Max. Your running speed has a linear relationship with the fraction of VO2Max you are working at. Let's say your VO2Max is 50 ml / kg / min (50 milliliters of oxygen per kilogram of body weight per minute) and your running speed is 300 meters / minute when you work at VO2Max. Then at 90% of VO2Max, which is 90% * 50 = 45 ml/kg/min, your speed will be about 90% * 300 = 270 meters / minute. When you run at 50% of VO2Max, you attain a speed of 50% of your speed of VO2Max. This is a direct linear relationship.

So what happens when you train and improve your VO2Max? Let's take an example. Let's say your VO2Max is 50 ml / kg / min and your comfortable effort level is at 80% of your VO2Max. At that effort level you will be consuming 80% * 50 = 40 ml of oxygen / kg / min.  That corresponds to a running speed of 80% * 300 = 240 meters / minute.  Now, let's assume that by training yourself you've raised your VO2Max to 60 ml / kg / minute.  Your comfortable effort level would be 80% of your new VO2Max, which is  80% * 60 = 48 ml / kg / min. That is a 20% increase over 40.  So now at 80% VO2Max your running speed will be 20% higher at 288 meters / min.  Alternatively, when you run at 240 meters / min you will achieve that speed at a lower level of effort.  Makes sense?

What does all this mean to your breathing when running?  Simple. You should breathe in such a way that you maximize the volume of air you intake in a minute.  Oh, by the way, as an interesting side note, the body's urge to breathe is more an attempt to get rid of the waste product Carbon Dioxide (CO2) than an urge to intake oxygen.  The body is quite comfortable with about 4-5% of CO2 in your lungs. But when you start running, your muscles produce much more CO2 than when at rest. When the body senses an increase above the normal 4-5% range you breathe harder to get rid of the excess CO2. It is the increase in CO2 that makes you breathe harder. Not the drop in the amount of oxygen. In fact, if oxygen were to be insufficient, you will simply pass out. We are fortunate that before that happens, the increase in CO2 drives us to breathe harder reducing CO2 buildup and increasing the O2 content in our lungs.

The air we breathe has plenty of oxygen. So all we need to do to deliver the maximum amount of oxygen to the muscles in a given amount of time is to intake maximum volume of air in that amount of time.  How does this translate to a breathing rate?  Let's again take an example of a runner who takes about 180 steps per minute (if you take fewer steps per minute, you should practice and get it up to at least 180 - probably a good topic for another "science the sh*t out of" post in the future :-) Let's say you breathe in for four steps and breathe out for four steps (a 4-4 rhythm). You are taking deep breaths and you'll probably move about 4 liters of air in and out of your lungs in every inhale-exhale cycle. How many breath cycle do you take in a minute?  That would be 180/8 = 22.5 cycles moving about 22.5*4 = 90 liters of air in and out of your lungs in a minute.  If you are working hard that is not very much.

Let's look at a 3-3 rhythm. Now you are breathing a bit faster and so the depth of each breath is a bit less. You'll probably move about 3.5 liters of air in and out of your lungs in every cycle. That would translate to 180/6=30 cycles yielding 30*3.5=105 liters of air in a minute. This gives you a lot more oxygen than the 4-4 breathing rhythm. Now let's look at a 2-2 rhythm where you inhale for two steps and exhale for two steps while taking the same 180 steps per minute. You are breathing a lot faster now which will reduce the volume of air further to about 3 liter per breath. At the 2-2 rhythm you get 180/4=45 cycles of breath in a minute moving 45*3 = 135 liters of air in and out of your lungs, which does an even better job of ventilating your lungs, reducing CO2 buildup and increasing oxygen intake.  A faster breathing rate of 1-1 drastically reduces the volume of air you can take in and also increases the portion of breath that moves through your mouth which doesn't get involved in O2 and CO2 exchange,  further reducing the efficiency.

You can now see why a breathing rhythm of 2-2 is most beneficial.  Most elite runners automatically switch to the 2-2 rhythm when running at sub maximal speeds. Practice breathing the 2-2 rhythm by mentally saying "in.. in.. out.. out.." to synchronize your breathing with your steps. Even when running easy try to get into this rhythm and make it a habit. You will deliver the maximum amount of oxygen to your muscles, helping you go farther and stronger.

Happy running.

If I can run, u can run