It is also called ATP-CP system, and it is based indeed on the use of CP [En2](creatine phosphate) which is a highly energetic molecule contained in muscles.

Like ATP, CP sets free a large quantity of energy by handing over its own phosphate molecule (P), consequently the P molecule binds itself to ADP (adenosine triphosphate), thus forming again ATP.

All these reactions happen without oxygen and thanks to particular enzymes which allow to speed every single reaction. Once exhausted, owing to a short, but very intense effort, the CP storage is re-established in around three minutes.

It is therefore the quickest available ATP source for muscles: it’s a powerful mechanism (large quantities of energy by unit of time), but with poor capacity as it exhausts its supplies in a few seconds (88% in 5.5 sec.).

Sports : athletics (sprint, throwing and jump), baseball, weight lifting, volley, dive, Graeco-Roman wrestling….