The Cori cycle is the metabolic loop by which lactate produced in working muscles travels through the blood to the liver, where it is converted back into glucose and returned to the muscles for fuel. Named after Carl and Gerty Cori, it explains how the body recycles the byproduct of anaerobic exertion rather than wasting it. During intense exercise, muscles outpace their oxygen supply and produce lactate; the liver’s reconversion costs energy but preserves precious carbohydrate. Sports nutrition builds on this understanding, with carbohydrate intake supporting the cycle and delaying the fatigue it postpones.