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. And we all know what this is like, you get that metallic taste in your mouth and your muscles just burn and you want to stop, that is the lactate catabolizing (breaking down) proteins in your muscle fibers. Well there is more to the story than simply excess lactate production. Calcium plays a role in this whole chaotic mess.
A new study out from researchers at Columbia University provides strong evidence for there being a link between calcium leaking inside muscle cells and muscle fatigue and degradation. The study found that after a few hours of intense physical activity, release channels on our muscles sarcoplasmic reticulum, begin to fail allowing calcium ions to continuously leak from them. As you may have guessed, sarcoplasmic reticulum sequester these calcium ions and then release them to control the contractile action of our muscle. When this controlled release mechanism fails though, the overflow of calcium ions actually weakens the contractile force that the muscle fibers are able to exert and also consequently activates a protein catabolizing enzyme. So not only are you getting weaker, but your muscle tissue is being slowly destroyed. OMGZ!!! You say… Well there is not much you can do about this fact. Our bodies simply are not designed to operate at intense levels of output for hours on end. There are drugs being researched, primarily for those with congenital heart failure, to mitigate the effects of this process and the hopes are looking good. As more research comes out, we will be sure to keep you informed. It is an exciting frontier in the study of muscle mechanics.
To leave on a slightly better note, there are supplements that can help us with the glucose to ATP conversion cycle, and by helping I mean increasing the efficiency of the process. D-Ribose, as in Deoxyribonucleic acid, is the base of most important molecules in the body. One of these important molecules is ATP. Studies have shown that by supplementing with D-Ribose, ATP production can occur more efficiently resulting in a slower buildup of excess lactate, meaning you can go harder for longer. Where can you find D-Ribose? Either as a pill or as a powder. As a powder it makes a good artificial sweetener and because it is a 5 carbon sugar, and not 6 like glucose, it will not raise your blood sugar levels or spike insulin levels! It dissolves easily also making it good for cold applications.
Hopefully you have left reading this article a little more informed that when you entered. Understanding the way our body works is the first step to improving the way we craft methods to change it as we may wish. Look for more in depth articles later.
Kathleen:
Hi,
That’s a great article. Perhaps if we can learn more about performance we’ll see less use of harmful supplements, especially from those in the professional sports arena.
Posted on March 1st, 2008 at 8:07 am