When a skeletal muscle fiber is at rest, its atp demands are met by

When a skeletal muscle fiber is at rest, its ATP demands are met by ADP and creatine phosphate. In a resting muscle, excess ATP transfers its energy to creatine, producing ADP and creatine phosphate. This acts an energy reserve that can be used to quickly create more ATP. When the muscle starts to contract and needs energy, creatine phosphate transfers its phosphate back to ADP to form ATP and creatine.