The ATP-PC system uses a stored molecule in the muscle called creatine phosphate (CP) to resynthesise ATP. It is the breakdown of this molecule that releases the energy needed to rejoin the ADP and free phosphate to form ATP.
Energy to resynthesise ATP is provided by the breakdown of creatine phosphate
This system is anaerobic as it works without oxygen, and does not produce any waste products. This system provides us with immediate energy but it is very limited and can only last up to about 10-12 seconds. It is therefore used for activities that involve short bursts of energy for example 100m sprint, long jump, high jump, shot put and javelin.