Few people think about how their lungs work when they start running.  For instance, did you know that our lungs are of different sizes?  Our right lung is wider and shorter than the left, which is narrower and longer.  The right lung consists of three lobes, but the left only has two lobes.  Why?  Because the left lung has a deep “cardiac notch”; it needs to allow room for our heart.  The right lung also has two bronchi, whereas the left has but one bronchus.  As a result, the right lung has approximately 15% more capacity than the left.

Our lungs have the ability to hold and move a certain volume of air.  Our lung’s Total Volume is approximately 6 liters (roughly a gallon and a half) for heathy adults.  Note: that’s TOTAL volume; lungs filled absolutely to the max.  We almost never go there.  What’s more important to us is our Tidal Volume, the amount of air which can be inhaled and exhaled during one respiratory cycle.  Tidal Volume is variable based on whether we are at rest or at max capacity effort.  Vital Capacity is the term for the maximum amount of air one can expel after a maximum inhalation.  Notice the change in terminology - we’ve gone from volume to capacity.  In other words, we’ve gone from talking about how much the tank can hold to how efficient the engine is.

The average healthy adult at rest has a Tidal Volume that is around 10% of Vital Capacity, or approximately 500 ml per inspiration (~7 ml/kg of body mass).  In other words, we’ve gone from  being able to hold 1.5 gallons of air, to actually moving around about 7 tablespoons worth of air.  As we start exercising, our need for air exchange increases, and can go up to over 50% of our Vital Capacity.  But we’re still only talking about 4 or 5 cups of air per breath!  How is it possible to run fast with that small of an amount of air exchange?   It’s because of the other dynamic at play — Respiratory RATE.  At rest, an adult averages around 10 to 16 breaths per minute.  As effort ramps up, so does the pace of our breathing, and it can max out anywhere between 60 to 100 breaths per minute, depending on sex, size, and training status (big differences to be had between the average Age Grouper and the average Olympian, obviously).  So 5 cups of air 100 times a minute gets that Olympian around 120 liters (30 gallons) of air.  PER MINUTE.  No wonder they’re so fast!

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