Understanding Muscle Fatigue
Ever wondered why it is we get tired, sometimes to the point where we can no longer even move our limbs. Muscle fatigue is a topic of intense research and study as biochemists and biophysicists seek to explain what exactly occurs in our bodies that leads to such exhaustion. The 100 year old theory that fatigue is due solely to lactic acid buildup in the muscle cells has recently been contested as two newly discovered factors now are seen as playing roles in muscle exhaustion.Let me start off by saying that this is going to be a technical article, not terribly so, but more than you might be used to. Do not be afraid though, by understanding what is going on in our bodies we can then train in more efficient ways.
The lactate model of muscle fatigue can be summed up by saying that after partial depletion of our bodies glycogen stores, glycogen phosphorylase (the fight-or-flight enzyme) steps in to convert the now depleted glycogen stores into glucose, the basic energy unit for all cellular functions. This process is called glycogenolysis; after this occurs the resulting glucose is then converted to ATP or adenosine triphosphate, the basic energy unit for all metabolic processes. This is as far in detail as we need to go but what is important to know is that this production of ATP via the degradation of glycogen is very inefficient and the faster rate of the oxidation of glucose versus absorption of lactate results in excess lactate production.
