The Immediate Energy system, or ATP-PC, is the system which the human body uses to generate immediate energy. The primary source of energy, phosphocreatine (PC), is stored within the body tissues. When exercise is performed and energy is used, PC is used to recharge ATP. Basically, the PC functions like a stockpile to help rebuild ATP in an almost rapid manner. So, in the quadriceps and hamstring muscle groups of an average athlete, a specific quantity of ATP and PC stored within the muscle. These stored substrates are ready and waiting to be chemically transformed to fuel biological work process – such as contracting a muscle. This system gives athletes a readily available store of energy which can be accessed without delay.
