English: Muscle activity is powered by consumption of ATP. Muscle fibers produce lactate when ATP demand exceeds the capacity of ATP production by oxidative phosphorylation (as a consequence of low oxygen concentration in the muscle). The Cori cycle links anaerobic glycolysis in muscle tissue to gluconeogenesis in the liver. The lactate secreted by the muscle cells is transported by the bloodstream to the liver, where it is converted into glucose via gluconeogenesis.