Day 114...'Thin Air' Exercising

I'm still not completely over my lackluster performance at the Prescott Punisher this past weekend.  While much of my poor performance was due to my poor nutritional preparation the night before...the altitude certainly played a big role as well.  I wanted to take this opportunity to share with all of you the 'scientific' side of this whole 'altitude' thing...I mean, come on...we all know the air is thin up there right?  But what does that really mean?

So here we go...let's take a little scientific journey, and learn about what really happens to the air at higher elevations, and why it is so hard to breathe sometimes...like last weekend!  If you're not into science...I recommend that you skip this post, and check back in a day or two.

Let's talk about air.  It's something that many of us take for granted...every second, of every day.  Our bodies perform an amazing function that allows air to travel into our lungs.  Once inside of our lungs, the body continues it's amazing feat, using that air to supply vital oxygen to tissues, and structures within our body, thus providing continued life.  But what is air made of?  This is something that most of us have learned at some point, in some science class, throughout our lives.  Like many other things we have learned in life though...we forget the details, and simply take it for granted.

Air...it's all around us.  We can't see it...well, sometimes we can...or at least the multitude of additional particles that become mixed into it.  Who out there remembers what air is made of?  Let's see a show of hands.  Hmm...I expected a better response!  Air is comprised of four separate gases.  I know...in 7th Grade Science class you were told that there were only two gases that made air...there are however, four.  These four gases are Nitrogen, Oxygen, Argon, and Carbon Dioxide.  There are actually other 'trace' gases present, but these four make up the greatest concentrations.  It is also important to mention that this is the makeup of dry air.  Water vapor can also be considered a component, and can be present in concentrations of up to 2%.  But for this discussion, we will keep the components limited to the four gases.  Each of these four gases is present in a specific concentration.  The largest component is Nitrogen 'weighing in' at 79.09% of the total concentration, while Oxygen follows at 20.95.  The remaining components of Argon and Carbon Dioxide are in such small concentrations (.93 and .039 respectively) that they are not usually taken into account when describing the components of what we know as air.

So...we've all heard it before...people saying things like, "The air is thinner at altitude" or "You can't breathe easy at high altitudes because there is less oxygen up there".  Which of these is correct?  Anyone care to take a guess?

In order to determine which statement above is correct, let's look at oxygen.  We know oxygen's contribution to the makeup of air is roughly 21% (20.95).  What happens when oxygen levels drop below 21%?  When this happens, we can experience symptoms such as lethargy, shortness of breath, dizziness, nausea, lack of concentration, etc.  Hmmm...sounds similar to what happened to me!  

It is important to know however, that oxygen levels do not begin to drop until we reach altitudes of 10,000 feet or greater.  Even at these altitudes, the percentage of drop is minimal.  Research suggests that significant drops in oxygen concentration happen at altitudes of roughly 70,000 feet!  I was only at 6,100 feet...so what the heck happened?

Atmospheric pressure has much to do with what happened to me.  Atmospheric pressure decreases with altitude, and as such, the air becomes less dense (or thinner!).  The air is less dense because each liter of air contains fewer molecules of gas.  This is known as the partial pressure.  A decrease in the partial pressure of oxygen has a direct effect on the saturation, or the amount of hemoglobin and oxygen transport within the body.  As a result, the body reacts in much the same manner as if it were being deprived of oxygen...because it is...but not because the oxygen content in the air was low, but simply because the partial pressure had been decreased.

So how does this affect athletic performance like cycling?  Maximal performances greater than two minutes in duration are primarily dependent on adequate oxygen delivery.  Therefore, any disturbance in the oxygen delivery process, such as decreased oxygen content or changes to the partial pressure of oxygen can lead to decreased performance levels...such as those that occurred during my last race.

So...let's revisit the original question.  Which of the statements is correct?  "The air is thinner at altitude" or "You can't breathe easy at high altitudes because there is less oxygen up there".  Technically speaking, both are correct.  However, since significant changes to the level of oxygen do not occur until altitudes of roughly 70,000 feet, the most common (and correct) answer to this question is that which refers to the thin-ness of the air, as this refers to the decreased partial pressure of oxygen.

Thanks for reading...I hope you learned something new today!