You have been jogging for two hours and you get painful cramps in your legs. the cramps are caused by a buildup of lactic acid from the process called

Anaerobic cellular respiration is used by the body in the lack of a certain reactant for regular aerobic cellular respiration. Usually this happens during exercise because it is harder for the body to provide both reactants for the chemical reaction; oxygen and glucose. When using anaerobic respiration the body is using the adipose tissue stored in the body to produce energy which produces 6 major waste products including Lactic acid.