© by IAAF 23:2; 103, 2008 The Lactic Acid System

1 TERMINOLOGY. by IAAF. 23:2; 103, 2008. The Lactic acid System (Related words: anaerobic glycolysis; anaero- Associated Myths bic lactate System ; glycolysis, glycolytic System ; Many think that Lactic acid or lactate cause lactacid System , lactate, Lactic acid , Lactic acid muscle stiffness and limit performance in running tolerance training). events. Neither is correct. Perhaps the most widely believed myth is that an accumulation of The Lactic acid System is an anaerobic ener- Lactic acid or Lactic acid crystals or lactate is the gy System in which the high-energy compound cause of the stiffness felt after a marathon or adenosintriphosphate (ATP) is manufactured long run. This stiffness is due mostly to damage from the breakdown of glucose to pyruvic acid to the muscle. Lactic acid exists only momentarily in the muscle cells. In the course of the and thus neither it nor Lactic acid crystals can process, known as anaerobic glycolysis (the accumulate in the body.)

2 The lactate released splitting of sugars), chemical energy is released from the muscle is converted in the liver to and used to synthesise two ATP molecules for glucose, which is then used as an energy each glucose molecule metabolised. source by the muscles during prolonged exer- cise. So, it actually helps to delay a possible low- During high-intensity activities, such as sprint ering of blood glucose concentration, a condition races, lasting up to about two minutes or for the called hypoglycemia that will cause a runner to first 40 seconds or so of less intensive exercise feel weak and fatigued if it occurs. (before the aerobic metabolism has been fully Another misconception is that Lactic acid or activated), the body uses the Lactic acid System lactate are responsible for acidifying the blood for energy. (acidosis), thereby causing the burn felt in intense exercise or the fatigue at the end of the 400m The pyruvic acid that is produced is con- verted to Lactic acid (C3H603), which very and creating the need for Lactic acid tolerance quickly dissociates into hydrogen ions and training or LATT.

3 This belief arises because the lactate. The end-product of glycolysis under level of lactate measured after intense exercise is aerobic conditions is pyruvate, a salt or ester high when the blood is acidic. The real cause of of pyruvic acid . acidosis is that every time an ATP molecule is split for energy, a hydrogen ion (known as a pro- Lactic acid and Lactate ton) is released and the accumulation of these Because the process of creating lactate lowers the blood pH making it acidic. Pyruvate involves a brief intermediate step in which Lactic molecules bond with protons to form lactate. acid exists, the terms are often used inter- Thus, lactate is a consequence of acidosis, changeably. But they are not the same: Lactic rather than the cause, and it actually keeps the acid is an organic acid that exists for such a acid level from becoming greater. short period in the body that it cannot be isolat- Sources: M.

4 Kent (2006). Oxford Dictionary of Sport Science ed or measured, while lactate is an acid salt and Medicine (3rd ed.). Oxford: Oxford University Press; S. that accumulates in the body, and this build up Jennett (2008). Churchill Livingstone's Dictionary of Sport and can be measured. The distinction is important Exercise Science and Medicine. Edingburgh: Elsevier; G. Thibault & F. P ronnet (2006). It is not Lactic acid 's fault. New not only for the sake of correctness but, more Studies in Athletics, 21(1), pp. 9-15;. importantly, because lactate and Lactic acid , have different physiological effects. ~lkravitz/Article%20 New Studies in Athletics no. 2/2008 103.