oxygen debt The situation that arises in an aerobic animal when insufficient oxygen is available for necessary metabolic functions (e.g. during strenuous physical exertion). Energy is supplied to muscles by the anaerobic conversion of pyruvate (ionized pyruvic acid) with the production of lactic acid which is stored in the muscles (and whose accumulation leads to the sensation of fatigue). When the exertion ceases and an adequate amount of oxygen is once more available, the lactic acid is conveyed to the liver and oxidized.

oxygen debt The physiological state that exists in a normally aerobic animal when insufficient oxygen is available for metabolic requirements (e.g. during a period of strenuous physical activity). To meet the body's increased demand for energy, pyruvate is converted anaerobically (i.e. in the absence of oxygen) to lactic acid, which requires oxygen for its breakdown and accumulates in the tissues. When oxygen is available again lactic acid is oxidized in the liver, thus repaying the debt.

oxygen debt Insufficient supply of oxygen in the muscles following vigorous exercise. This reduces the breakdown of food molecules that generate energy, causing the muscles to overproduce lactic acid creating a sensation of fatigue and sometimes muscular cramp.