The body utilizes stored ATP and the creatine phosphate system when ATP demands exceed cytosolic production capacity, and these systems do not necessarily require oxygen.

“However, when the ATP demands even exceed the cytosolic production of ATP, that's where you need to use the ATP that is already stored in the muscles. You just don't have time to synthesize it. You need just to use it. And that's why the body stores very, very minimal amounts of ATP. And that's what you develop in the sprint or you use in the sprint. but you need to resynthesize it very fast. That's the pure anaerobic. You don't need any energy systems. And that goes also that of the confusion that is out there too. And are you saying this is distinct from the creatine phosphate system? Yeah, you can use a creatine phosphate as well.”