The ATP/PC System
This is the third energy system, and my personal favourite. It is also know as the ‘Gain’ System.
This is the money maker energy system. It is our primary feeder of energy for all the cool stuff, heavy lifting, sprints and explosive movements in sport like a golf swing, or tennis serve.
During the first few seconds of exercise regardless of intensity, the ATP-PC system is relied on almost exclusively, with energy coming from the breakdown of the ATP stores within the muscles. These ATP stores last only a few seconds after which the breakdown of PC provides energy for another 5-8 seconds of activity.
How Does It Work?
Steps of the ATP-PC system:
1. Initially ATP stored in the myosin cross-bridges (microscopic contractile parts of muscle) is broken down to release energy for muscle contraction. This leaves the by-products of ATP breakdown: adenosine diphosphate (ADP) and one single phosphate (Pi) all on its own.
2. Phosphocreatine (PC) is then broken down by the enzyme creatine kinase into Creatine and Pi
3. The energy released in the breakdown of PC allows ADP and Pi to rejoin forming more ATP. This newly formed ATP can now be broken down to release energy to fuel activity.
ATPase in this case assists the synthesis of new ATP rather than the breakdown. We see how this works in the diagram below.
How Long Does It Last For?
Combined, the ATP-PC system can sustain all-out exercise for up to 10-15 seconds if activity continues beyond this immediate period, the body must rely on other energy systems to produce ATP as the limited stores of both ATP and PC will be exhausted and will need time to replenish.
These stores are replenished after about two minutes rest. If activity continues at a high intensity these stores may only partially replenish as there will not be enough energy available for creatine and Pi to reform PC and the rate of ATP breakdown through other energy systems will impede the replenishment of ATP stores in the muscle.
When Is It Used?
This system as mentioned is above only lasts for 10-15 seconds max. This means this system is only going to be used the most during high intense, short maximum efforts of work.
So, think a heavy back squat, 100m sprint, long jump etc.
You would only use this in classes for the very beginning of movements, or exercises in classes, as the majority of time you aren’t going for only 10 seconds – more like 45 so once that time threshold has been hit you will then transfer to another energy system.
How Do I Improve It?
Two things to think about here with regards to how to develop this system.
You need to make sure you are targeting this energy system correctly so short, maximum efforts of work lasting 8-10 seconds. Once you have worked on this system for a while you could try to push this up to 15 seconds.
Specific exercises or movements you can do to target this system are:
Heavy weight training for 1-3 repetitions.
Sprint drills / work (running, ski erg, rowing)
Jumps (for how they are supposed to be used not stupid box jumps for 45 seconds or 80 reps like in crossfit).
To specifically target the energy system and develop it you need to allow it to recover fully between work periods.
There is a more scientific formula for rest periods called the ‘work to rest ratio’. For the ATP-PC system the rest ratio is 1:10/12. This means that for every second of ‘work’ you need to allow 10 to 12 seconds for recovery.
You can easily implement these sorts of sessions into your training program as you can easily get great work done within 20 minutes. This system is definitely aligned with the old saying of Quality over Quantity!!