You are currently viewing “Our Little Furnaces” Our energy systems

“Our Little Furnaces” Our energy systems

We can just think of our Energy systems as a furnace, we produce energy by producing Heat, but in fact we have 3 energy systems that work in tandem.


The ATP-PC system (Phosphagen) system is the first system used in any exercise routine, it is used for Maximal Burst of Strength and Speed, it utilises Phosphagen and no Oxygen, this system is very quick indeed and only 3 – 4 seconds. This is an evolution of the “Flight or Fight Response”.

2) Anaerobic Glycotic System

As soon as exercise is started and for events up to 90 seconds 60% of the Energy will come from this source dropping to around 35% after 2 minutes.

As an energy source this uses only Glycogen, this energy system has a rapide build up of Lactic Acid and pain is felt through the build up of Hydrogen.

3) Aerobic System

This system generates ATP from FAT (Lipolysis), this system cannot produce ATP as quick as the other two systems but can produce larger amounts and for longer.

This system also uses Muscle Glycogen and Glucose from the bloodstream.

After 2 hous exercise at greater than 70% VO2 Max all muscle Glycogen is depleted.

The Aerobic Energy system is 20 times more efficient as it uses both Glycogen and Fat.

It can be seen that its possible all 3 of these energy systems will be used in order during an exercise session.

How does the Body decide whether to burn Fat or Carbs?

Depends on:

* Intensity of Exercise
* Duration of Exercise
* Your Fitness Level
* Pre exercise Diet

The Good News is as you get fitter your body becomes better at burning FAT as exercising produces more Mitochondria which are used for Oxidising.

Leave a Reply