ATP-CP energy system

As the body exercises it has an increasing demand for energy. In order to perform fast explosive movements the ATP-CP energy system is used to quickly provide this energy. This system uses the molecule creatine phosphate (CP) by breaking the high energy bonds between the creatine and phosphate atoms to provide energy for the synthesis of ATP which can be used as energy for muscle contraction.



The creatine phosphate energy system is relatively simple, the bond in the creatine phosphate molecule is broken this provides enough energy to reform the bond or add on another phosphate molecule onto adenosine diphosphate(ADP) to form adenosine triphosphate(ATP) which can be used to supply energy for the muscles. This system provides energy quickly as it is anaerobic meaning it does not require oxygen to occur hence it is not limited by oxygen supply and due to the small number of reactions can occur at an extremely fast rate.

Key Aspects of the CP-system

Fuel Source

The creatine phosphate molecule(also known as phosphocreatine (PC)) is stored in limited supply in the muscle. It is obtained through our diet and can even be found in some supplements. The molecule contains  high energy bonds which can be broken to provide energy.


Creatine phosphate(CP) is stored in the muscles however in small supply. This is why it can only be relied on for a small amount of time before the use of other energy systems are need to provide sufficient energy. CP stores are replenished with passive recovery with around 70% of stores replenished in 30 seconds and 98% in 3 minutes.

Intensity of activity:

The CP system is usually used for high intensity activities that are around 95% of max heart rate. Hence require fast production of energy.


The ATP-CP system is usually the dominant contributor to energy at the beginning of maximal exertion for 1-5 seconds with a total duration of 10 seconds before the system runs out of creatine phosphate molecule and the body must rely more so on the other energy systems.

Peak effectiveness (power)

The ATP-CP is most effective in the time period of 2-4 seconds this mean it is providing energy at it greatest rate before stores begin to decline restricting its effectiveness.

Rate(Speed of ATP production):

This energy system provides energy at an instantaneous/explosive rate as the system relies on simple and fast chemical reactions.

Yield(Amount of ATP produced)

The yield is very low as the small number of reactions do not allow for the synthesis of large amounts of ATP. The yield is around 0.7 mole ATP per CP molecule.

By-Products of this system

Are creatine(C) and inorganic phosphate (Pi). Inorganic phosphate can be a potential harmful by-product as it can interfere with the process of muscular contraction.

Advantages of the ATP-CP system

  • Extremely fast synthesis of ATP.
  • Useful for high intensity/ explosive activities.

Disadvantages of the ATP-CP system

  • Yield is low meaning ATP is synthesised in limited amounts
  • Limited stores of ATP and CP in the muscle
  • Produces inorganic phosphate as a harmful by-product.

ATP as an energy storage molecule

Adenosine triphosphate(ATP) consists of one adenosine molecule with three phosphates connected to it as seen in the image below. Energy is stored within the bonds of the phosphate molecules, when these bonds are broken (usually the bond between the two end phosphate molecules) the energy can be used for muscle contraction or other process that require energy. The body uses ATP as a temporary storage molecule as the end product to provide energy, hence all the energy systems in the body provide energy for the synthesis of ATP which is ultimately used to provide energy for muscle contraction. When the bond between the last two phosphate molecules is broken adenosine diphosphate(ADP) and an inorganic phosphate(Pi) are formed, an organic phosphate will then need to be reattached to synthesise ATP and this process requires energy.1

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  1. Live it Up 2 textbook, Jacaranda