ATP-PC system & Fast Twitch Muscle Fibres

Hi people, thank you for taking the time out of your day to read this blog, let me know what you think to it in the comments section at the bottom, and also what you would like seen covered in later blogs :) 

In this blog, as the title suggests I’ll be talking about the ATP-PC energy system, how it works, what muscle type is most associated with this system and how the system can be trained for optimal efficiency. 

So basically our bodies energy supply is in constant need, and ATP (adenosine triphosphate) is the compound needed for energy and therefore body movement. The ATP-PC system utilizes small amounts of ATP already stored in the muscle for an immediate energy source. Once the ATP runs out, (a matter of seconds) more ATP is formed from the breakdown of phosphocreatine (PC) which is an energy compound found in the muscle. This energy source will last for around 10 seconds. So all in all the best use of this system is between 10-15 seconds. It is the quickest of the 3 energy systems to create energy needed for movement and also the quickest to run out of the energy needed. Once all PC is depleted, it takes around 2-3 minutes for it to replenish its stores. It is anaerobic which means it does not use oxygen. 

So how many of you take creatine? Creatine is recognised to be the god among supplements, but what does it actually do? and why is it relevant to this blog?. Well… when taking creatine, the creatine becomes saturated into your muscles and will increase your PC (phosphocreatine) stores. This in turn allows your body to produce more quick energy and can give you that extra rep in the gym. Its pretty much a ATP-PC system booster/enhancer. 

Theres not a certain time in the day to take creatine, its not like a pre-workout. As long as you take it at some point throughout the day each day, then you will saturate your muscles with it and the effects will take care of itself.

So thinking logically, what sort of exercises or sports would most likely be using this energy system to its full advantage? Basically anything that involves up to 10-15 seconds of maximum intensity. Sprinters and powerlifters are probably the best 2 examples. 

To train this energy system you will want to perform repeat up to 10-15 seconds of maximum intensity work. Making sure you rest in between for 2-3 minutes to allow stores to replenish. This could be sprinting 50-100m maximum effort with 2-3 minutes rest before going again. Or performing 1-5 reps of a compound exercise lift (maximum effort but keeping strict form), with again 2-3 minutes rest in between. 

If you don’t allow sufficient rest periods, the energy system you require for the maximum lifts will not have fully replenished in time, therefore impeding your strength on the next lift and holding back your real potential. It will also force your body to tap into the other energy systems and you will be starting to train endurance which will be counterproductive to developing explosive strength. 


We have 3 main muscle fibre types in our body. Type 1 : This is for more long endurance activities, also known as slow twitch. Type 2a muscle fibres and Type 2b.

Type 2b is the most relevant to this blog as these muscle fibres, like the ATP-PC system are recruited for very short-duration high-intensity bursts of power. These muscle fibres are also known as fast twitch muscle fibres. They have a tendency for higher hypertrophy (muscle growth) 

All humans have different amounts of each muscle fibre types predisposed. Usually, professional athletes have taken full advantage of their most prominent fibre type and therefore exceed in there sport. 

For instance, for the most part, sprinters will be predominantly made up of fast twitch muscle fibres, where as marathon runners will have an abundance of type 1 (slow twitch) muscle fibres.

Going back to Type 2b (fast twitch) muscle fibres being more prone to muscle growth, all you need to look at are the physiques of a sprinter compared to a long distance runner. Notice that the sprinters have a lot more muscle mass in comparison. This will be due to their muscle fibre makeup and the way they train. Therefore if you are looking to increase muscle mass, don’t be running too many marathons ;) 


Just to finish off, the image above gives a great representation of the uses for each muscle fibre type.

Hope this was a good read for you guys, and see you in the next one :)



  • – Akeqolu Isoirofum

  • – Ikvokoqo Oukuiibob

  • – Akeqolu Isoirofum

  • – Ikvokoqo Oukuiibob

  • – Ihusat Uzahmi


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