Thursday, September 29, 2016

Relationship between aerobic and anaerobic metabolism

Some coaches will speak of the elements of performance as exclusive concepts. Aerobic and anaerobic metabolism for example. Traditionally, the two could be separately defined, but we've known for some time now that the two are essentially bound in a symbiotic relationship. They're both a piece of the pathway that creates ATP.

A typical physiological response from high intensity intervals, sprints, a finishing kick or a high intensity (<30 min) race is an accumulation of lactate and H+ ions. We know an accumulation of H+ ions (acidosis) will decrease performance capacity. The table below from Cairns, 2006 lists some proposed mechanisms through which acidosis inhibits performance.

If only there were a mechanism in place to remove these pesky ions... Then, we could perform at a higher intensity for a longer period of time.

But wait, there is!

Oxidative phosphorylation, more commonly known as the electron transport chain or "aerobic metabolism," consumes H+ to reduce O2 to H2O. Not only does it consume H+, but it does so to produce more ATP! Essentially, glycolysis (anaerobic metabolism) provides the aerobic pathway with substrate  (H+) for ATP production.

This is our link between anaerobic and aerobic metabolism. Aerobic metabolism helps prevent or delay acidosis by consuming the substrate, commonly regarded as a "byproduct," produced by glycolysis (H+) to synthesize more ATP! By consuming H+, oxidative phosphorylation also helps to maintain redox potential -- otherwise, gylcolysis would be inhibited by the accumulation of NADH and H+. Oxidative phosphorylation then, is a double-whammy, win-win. Not only does it produce ATP, but it also consumes H+ so you can continue to produce more ATP.

So, let's drop this "Aerobic vs. Anaerobic" nonsense and recognize they both contribute to fitness and performance. The limitation is not aerobic or anaerobic metabolism, it's simply ATP production. If you want to go faster, you need to train to produce more ATP.

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