Understanding How Your Body Produces Energy - THE ATP/ADP SYSTEM

[icewind]

Just waned to post this, for all you interested in how the body produces it's energy.

What is ATP?
ATP (Adenosine triphosphate) is obtained by basically breaking down glucose in a process called Glycolysis (anaerobic) and it is the energy currency of the living cell. In other words it is the basic form of energy for the body.

The body has four methods to create ATP, they vary by speed, and by whether they burn oxygen or not.

Explosive Force - The ATP-CP System: ADP + Creatine phosphate (CP) ==> ATP + Creatine. By far the fastest way to get that third phosphate group is to grab it off of a molecule called "creatine phosphate" or CP, that's why creatine supplementation helps especially with heavier/explosive weightlifting. When you are doing very explosive exercise for 10-30 seconds, such as an all-out sprint for example, the burst of energy is delivered by the ATP-CP system. Fast, doesn't require oxygen, but extremely limited to short periods of explosive force. ATP-CP system usually recovers 100% in about 3 minutes. That is reason why when doing powertraining 1RM your recomended rest time should be 3 minutes.

Sugar Burning - Step 1 (Anaerobic Glycolysis): ADP + glucose ==> ATP + pyruvic acid (which converts to lactate if not burned with oxygen). The next fastest method of getting energy is to turn a sugar molecule into lactic acid. This doesn't require oxygen either. This system is effective for vigorous exercise of between 1-3 minutes in duration. When the intensity of the exercise requires more energy than what can be burned with the oxygen you are breathing, your body starts "partially" burning glucose anaerobically (without oxygen). This is the system you want to be using during "wind sprints". This is a system that has to be trained in order to get fast results, but again, this system can be used only for a limited period. As lactic acid builds up in your muscles, you start to feel them "burn". If you go beyond a few minutes of this, the acidity of the muscle tissue increases and the muscles start to have difficulty generating meaningful amounts of energy.

Sugar Burning - Step 2 (Aerobic Glycolysis): ADP + lactate + oxygen ==> ATP + water + carbon dioxide. This is the next system, and for all practical purposes is the one you use most often when exercising. Once glucose has been converted to lactate anaerobically (without oxygen), the body then burns the lactate using oxygen to create more ATP.

The sugar burning Step 2 will theoretically burn the highest amount of calories. For example when doing a cardio exercise such as running etc.

Fat Burning (Aerobic Lipolysis): Fat + oxygen + ADP ==> ATP + water + carbon dioxide. This is by far the slowest system. It is, in fact, too slow to contribute extensively to energy production during exercise (in fact, if you ever deplete your glycogen stores so much that the body has to rely on lipolysis for its energy, your muscle movement slows down dramatically). In order to mobilize fat, a "triglyceride" has to be broken down into fatty acids, bound to proteins, and other time-consuming feats. The good news, is that lipid (fat) metabolism is the main way that your glycogen stores are replenished after exercise. That's why it can be useful to work out in the morning on an empty stomach and wait about an hour after your workout before eating - your glycogen stores are more depleted by the end of your workout and you burn more fat afterward.

Source: IceWind and Institute of Sports Medicine.