What is aerobic and anaerobic exercise?

Generally, without getting specific, in terms of running, aerobic is easy running. Easy enough that you can talk comfortably while running. Anaerobic is when your heart rate climbs to 170 or above for most, accumulating lactic acid in the muscles as a result of not having the proper levels of oxygen to burn. Aerobic exercise burns fat, anaerobic exercise will not. Others, jump in........

A bit off on the idea the anaerobic metabolism takes place when there is no oxygen left in the body to use. Brooks, et al. have shown that O2 is always present.

Aerobic simply refers to the generation of energy using oxygen. Anerobic refers to the generation of energy not using oxygen (different than saying in the absence of oxygen.

Oxygen is present at all times in the circulatory system and is available for energy production, but when exercise intensity raises to high levels, an individual may not be capable of processing what is available at the rate needed to keep up.

Think of energy production as an ever-increasing steep hill that you run. As the hill gets steeper more engergy is needed, exponentially, to keep going. Since aerobic metabloism is rate-limited by such things as blood chemistry and quantity, vascularization of muscle tissue, heart strength, enzygme levels within the mucle fibers, substrate (carbs, fats, prot.) availability, anaerobic processes are initiated to meet the high energy demands that aerobic processes can not fulfill alone.

In certain case, anerobic processes provide the vast majority of energy. For example, if you were to sprint from a dead stop, you would be using primarily anerobic processes for the first few seconds. Aerobic processes are not capable of generating energy instantly and in such great quantities as sprinting all-out. However, as you run farther and farther, aerobic processes dominate the amount the proportionality of energy created because it would be too tiring to keep up super-high engery production via anaeobic processes.

There is more to it than what I have ambition to describe here, so I will close by saying that we always have oxygen when running (unless we are suffocating from some massive bug in our throats) but certain circumstances don't allow us to use all of it. Tom

Tom,

So then while running anaerobic you still are producing oxygen but the body cannot produce enough oxygen to keep up with the demand of the activity. So because of the insufficient amount of oxygen available the rate of exercise cannot last long. Am I close? How long can one be in total anaerobic before "running out of gas?"

I was reading and came across this:

http://www.physsportsmed.com/issues/2003/0503/wilmore.htm

bump

Replace produce with intake or consume and you're close dsf.

You produce energy through three different pathways: ATP-CP System (also called phosphogen system), Glycolysis, and Oxidative Phosphorlation. The first two (ATP-CP and Glycolysis) produce energy outside of the cell and don't require oxygen to produce energy, thus they are termed "anaerobic". Oxidative Phosphorlation requires the use of oxygen to produce energy and is termed "aerobic"

The ATP-CP system is basically the use of your stored ATP (which is the energy currency of the body, you need ATP to do everything you do) and the regeneration of the used ATP. ATP is broken down to ADP and energy is released. In your body CP (creatine phosphate) is also stored and this CP can be used to regenerate the ADP to form ATP and the cycle repeats itself. The limit of this system is about 10 seconds of all out work.

The Glycolytic system uses glucose from the breakdown of carbohydrates to form ATP. It produces a net of 2 ATP and the limit is about 2 minutes of all out work. The end products of Glycolysis are pyruvate and hydrogen. What happens to these byproducts depends on what is going on in the mitochondria of the cell. Basically, if there is enough oxygen present in the mitochondria and the mitochondria are not "backed up" then the pyruvate will be sent to the mitochondria and used in Oxidative Phosphorlation and the hydrogen well be sent to the Electron Transport chain and used to make ATP. If the mitochondria are "backed up" then the hydrogen and pyruvate will combine to form lactic acid which is then buffered into lactate and sent to the bloodstream.

Oxidative Phosphorlation can use glucose, fat and even protein to make ATP, the net yeild being 39, 18 times more than Glycolysis. As discussed previously glucose is broken down in glycolysis with the end result being pyruvate and hydrogen. Both fat and to a lesser extent protein are involved in oxidative phosporlation. The pyruvate from glycolysis, the fatty acids, and protein can all be converted to acetyl-CoA in the mitochondria. Acetyl-CoA is sent through the Krebs Cycle which then releases hydrogen. This hydrogen is then sent to the Electron Transport Chain. Oxygen comes into play only in the last step of the Electron Transport Chain. The hydrogen protons become separated from their electrons and from these electrons ATP can be produced. So, at the end of the chain we have a bunch of hydrogen. Oxygen combines with hydrogen to form water so the cycle can continue.

So, if there isn't enough oxygen present the mitochondria become "back up" and if the pyruvate from glycolysis can not find any mitochondria to enter then it combines with hydrogen to form lactic acid. So we see that an increase in oxygen to the mitochondria and the increase in number of mitochondria will lead to a greater "aerobic" ability.

During any activity you will used all three systems. Even at the beginning of an easy run you will use the ATP-CP system. You are also never running 100% "aerobic". There will always be some energy produced through Glycolysis and some lactate build up, but not enough to cause fatigue.

Now you have a simple breakdown of the three energy systems.

Alan

Couple good physiology sites:

http://home.hia.no/~stephens/exphys.htm

http://www.simpsonassociatesinc.com/physlgy.html

Can you run for an hour continuously anaerobically?