The human body has two main energy system it gets the energy from. The aerobic and the anaerobic system. Whats is that and when does the body use which?
All human cells can only use ATP to create power. Phosphate, carbohydrate and fat needs to be transformed into ATP first which happens at different speeds.
No oxygen and no lactat. Sound like this energy source is not very sustainable. Right. The body has ATP reserves for about 7 seconds. During that short time it is possible to perform at your max power. Your body does not need to transform carbs or fats into ATP which takes time but can directly access your ATP and phosphate storage. Afterwards the power output drops significantly. The anaerobic, alactacid energy system is essential for sprinter and weight lifter.
Glycolysis above the lactate threshold – anaerobic lactic
No oxygen but lactate instead. During a final spurt when you are out of breath, your legs burn and you need to give all you got your body is running above the lactate threshold. The energy source is the glycolysis which runs anaerobic lactic. Because of the lack of oxygen a fat metabolisms is hardly possible. The body burns carbohydrate even without oxygen. This creates large quantities of lactate which make it impossible to perform more than 1-2 minutes at this level.
The lactate threshold describes is the intensity where the body starts to create more lactate than it is able to metabolize.
Glycolysis below the lactate threshold – anaerobic lactic
There is some oxygen and the lactate can be broken down faster than it is created. A typical scenario is a 10km run. During those 30 – 60 minutes carbohydrate is the main energy source. The way ATP is created is the same as above the lactate threshold. The difference is the rate lactate is being produced and broken down.
Lipolysis – aerobic alactic
This is the main energy source for endurance athletes. Why? The carbohydrate store lasts only for about 90 minutes. After that point the only energy source is fat. Even the leanest athlete has almost unlimited fat resources. However transforming fat into ATP is relatively slow. For endurance athletes it is therefore very important to improve their performance in the aerobic zone.
It is important to understand that cells use all energy sources at all times. What changes is the share each fuel source has on the total energy production. Even at rest the anaerobic lactic system is working on a low level.