When activity intensity is high, the body has to produce energy quickly. Energy can be produced through aerobic as well as anaerobic metabolism. The production of lactate is the final step in the glycolytic pathway where pyruvate is broken down to form energy. The concentration of lactate can increase more than tenfold in physical exertion but the rise is of short duration and depends on the oxygen supply to the tissue. One consequence of this is that a particular tissue can produce lactic acid during exertion while several other tissues may still have a good supply of oxygen.