|MadSci Network: Biochemistry|
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. Chris
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