Lactic acid is a waste product that is produced by muscle tissue and red blood cells. The body normally breaks down carbohydrates into water and carbon dioxide when oxygen levels are high. However, during anaerobic metabolism, when oxygen is no available for the oxidation of hydrogen atoms, cellular oxidation of the hydrogen cannot take place. Small amounts of energy may be released through the initial breakdown of glucose into pyruvic acid. With extended periods of decreased oxygen, the end products of chemical reactions build up. The build-up of hydrogen and pyruvic acid leads to lactic acid formation through chemical reactions. In the absence of oxygen, lactic acid cannot be broken down and it accumulates, resulting in metabolic academia. When an exercisers “feels the burn”, he or she is actually experiencing excess lactic acid levels in their muscles. Very high amounts of lactic acid can be hazardous, and even life-threatening. Fortunately, the buildup of lactic acid is a condition that can be reversed; when body tissues are exposed to sufficient amounts of oxygen, the lactic acid is metabolized and body systems return to normal.