MadSci Network: Biochemistry

Re: Why is hyperventilation useful before a dash?

Date: Mon Nov 22 18:52:18 1999
Posted By: Chris Larson, Post-doc/Fellow Laboratory of Genetics
Area of science: Biochemistry
ID: 934920262.Bc

Dear Kristen,

I will answer your question in two parts.  First, there is no benefit to 
hyperventilation.  Hyperventilation, which consists of taking short, quick 
breaths in rapid succession, seems like a way to get more air in your 
lungs.  However, researchers have shown that (i) you take in a smaller 
volume of air than when you breath normally, and this leads to (ii) an 
increase in the concentration of carbon dioxide and decrease in the 
concentration of oxygen in both your lungs and blood.  Certainly 
hyperventilation before any exercise is counterproductive, and after 
exercise athletes are encouraged to take as deep of breaths as possible 
since this will speed the exchange of carbon dioxide for oxygen.

The second part of your question is very interesting.  During vigorous 
exercise, your skeletal muscles are working anaerobically, and as a result 
the rate of conversion of an enzymatic cofactor called NAD+ into NADH by 
glycolysis (during the production of pyruvate) exceeds the rate of 
conversion of NADH into NAD+ by the respiratory chain. Since your body 
needs NAD+ so that glycolysis in skeletal muscle can continue (glycolysis 
is where the energy to run your muscles during exercise comes from), and 
the "normal" reversion of NADH back into NAD+ by the respiratory chain is 
not fast enough, your body actually converts pyruvate plus NADH into 
lactate plus NAD+.  This NAD+ is then used to continue glycolysis.  The 
interesting thing is that lactate is a biochemical "dead end" in 
metabolism: it has no use and must be converted back into pyruvate before 
it can be metabolized.  Essentially what is going on is that the body is 
buying time by shifting the metabolic burden of dealing with the lactate 
from the muscle to the liver, but is using the NAD+ that is made in the 
muscles to continue exercising.


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