processes that occur in muscle energy systems
ATP and creatine phosphate (or phosphocreatine, or PCr) make up the ATP-PCr system. it is the immediate energy system. Creatine phosphate (PCr) is a high-energy compound. When evercise intensity is high, or energy needs are instantaneous, creatine phosphate stored in muscle is broken down to provide energy to make ATP.hen ATP is broken down, it gives energy for muscle contraction. It is the only molecule that can supply the energy used in the contraction of muscle fibres and can be made in three ways: the creatine phosphate system which is also called Phosphocreatine, the lactic acid energy system and the aerobic energy system.