ATP-PCr system

An anaerobic energy system in which the generation of ATP is coupled with the exergonic (energy-releasing) breakdown of phosphocreatine stored in muscle cells. The breakdown frees inorganic phosphate, which then combines with ADP to form ATP. The ATP-PCr system is the quickest source of ATP for muscle actions. Athletes in power events lasting up to 10 s (e.g. 100 m sprints) derive most of their ATP from this system.