Immediately after its ATP is consumed, a working muscle relies on DIRECT PHOSPHORYLATION OF ADP BY CREATINE PHOSPHATE to regenerate ATP for contraction.
There are three different systems which provide energy for a working muscles depending on the duration of the work that the muscle is doing. Immediately the stored ATP in a muscle is consumed, the first system that will be activated for production of ATP is direct phosphorylation of ADP to ATP. Followed by anaerobic glycolysis and gluconeogenesis.