Enzyme Wars

For an endurance athlete - the VO2 max value - the maximal oxygen consumption value sets the ceiling for high sustainable work rate. It is a measure of his performance engine!! This is where Lactate Threshold (LT) and enzymes come into picture - greatly influencing how much power this engine is able to deliver.

We all have experienced muscle fatigue while running, pumping weights - it is due to the lactic acid produced by the muscle, and if this accumulation goes unchecked the decreased cellular pH may cause muscles to shutdown.

Most of the energy (ATP) required for endurance work comes from the glycogen stored in the muscles. Endurance work causes this glycogen to break down (glycolysis) into glucose again through enzymatic reactions not requiring oxygen.

Glycolysis results in two pyruvate molecules that are like a leaf floating in the river, they have no say in the metabolic direction to take!!

This is when the enzyme wars begin!

Two enzymes pyruvate dehyrdrogenase (PDH) and lactate dehyrdrogenase (LDH) compete for these pyruvate molecules. If the mitochondria is efficient, then PDH keeps shuttling the pyruvate into the mitochondria, where it further breaks down through oxidation to yield high ATP per glucose. If PDH can't keep up then LDH starts to win - the pyruvate gets converted into lactic acid, and as enough of it accumulates the body begins to approach the Lactate Threshold, and the engine slows down!!

So, as a whole, the body - heart, liver, kidneys, and the circulatory system should be very healthy so that this increased production of lactic acid can be quickly taken back from the blood, and converted back into pyruvate or resynthesized as glucose (in the liver).

I'll stop now, I'm approaching LT ;) ...