Energy Systems (Simplified)

Sometimes referred to as 'Pathways' can be confusing so i will keep it simple.
There are 3 systems;


1. IMMEDIATE ANAEROBIC - produces energy for 0-10-seconds and relies on stored body chemicals for fuel such as creatine phosphate (CP) and adenosine triphosphate (ATP).
If there is full recovery between repetitions then these chemicals will quickly replenish  thus allowing the system to provide immediate energy .


There is NO reliance on oxygen as an energy source. This system would, for example, fuel a 40 metre sprint or punch combination, tennis serve or javelin throw.

2. SHORT-TERM ANAEROBIC - produces energy for 10-90 seconds. Just like system above it relies primarily on stored body chemicals as the prime fuel source, however as the 90 second mark approaches more oxygen is used to try to sustain the high exercise intensity. That said, no amount of oxygen uptake is ever going to provide enough energy to keep this system going.
 Its a bit like lighting a fuse attached to a stick of dynamite. The fuse consumes itself, burning more oxygen as it does and then blows the dynamite up. Translating this to exercise means, if you were to start running as fast as you could , you too would 'blow up' (well not in the same way, but you catch my drift!)
This is the type of energy required for a 400 metre run.

3. AEROBIC - produces energy potentially for hours and relies on oxygen to fuel a chemical reaction in your muscles to keep them working. 
This is the type of energy required for a marathon.

In reality a mix of these systems are used but depending on what sport / activity / exercise/ intensity you are doing will dictate which system is used the most. You need a good AEROBIC (means with oxygen) fitness base as a foundation to build ANAEROBIC (means without oxygen) systems upon. High intensity is a hugely efficient way to train BUT steady state training serves its purpose to achieve an AEROBIC training effect which underpins everything.

Hope this breaks down what can be a confusing subject area !