Lactic acidosis, which occurs when athletes push themselves beyond their abilities, is temporarily debilitating but usually not long-lasting. It is the result of overproduction of acid resulting from metabolic cellular processes carried out in the absence of sufficient oxygen. The details of the biochemical reactions that produce the byproducts responsible for acidosis are the subject of debate among biochemists.
The Problem
Exercise-induced lactic acidosis is a subtype of metabolic acidosis in which an excess of acid builds up in body fluids as a result of exercise so intense that muscle cells cannot get enough properly oxygenated blood. In the absence of oxygen, cells continue to generate energy, but they are forced to use an alternative biochemical pathway, which releases byproducts that make blood plasma acidic. It is widely believed that accumulation of lactate is one of the reasons muscles tire during intense exercise and that lactate production causes acidosis.
The Source of Lactic Acidosis: Explanation 1
The traditional biochemical explanation for exercise-induced lactic acidosis insists that increased production of lactic acid is responsible for the buildup of acids responsible for the condition. This process involves the release of a proton and the acid salt sodium lactate. When an excess of these byproducts accumulate, the body cannot buffer or neutralize them and blood plasma becomes acidic.
The Source of Lactic Acidosis: Explanation 2
Robert A. Robergs, of the Exercise Science Program at the University of New Mexico, and scientists who agree with him claim, as Robergs wrote in SportScience.org, that "the widespread belief that intense exercise causes the production of 'lactic acid' that contributes to acidosis is erroneous." Researchers in this camp argue that lactic acid production is not the cause of lactic acidosis; it is instead a consequence of the metabolic processes that cause acidosis.
"Increased lactate production coincides with cellular acidosis and remains a good indirect marker for cell metabolic conditions that induce metabolic acidosis. If muscle did not produce lactate, acidosis and muscle fatigue would occur more quickly and exercise performance would be severely impaired," Robergs writes in the September 2004 issue of the "American Journal of Physiology." The issue remains controversial. For example, Dieter Böning, of Sports Medicine, Charité-University Medicine, in Berlin, Germany, and Norbert Maassen, of Hannover Medical School in Hannover, Germany, concluded in the July 2008 issue of the "Journal of Applied Physiology" that there remain no arguments for other acids or other mechanisms of acidification. Lactic acid, they insist, is the main cause of exercise-induced acidosis.
Treatment
Whatever the ultimate biochemical basis of lactic acidosis, rest is often sufficient to allow recovery from the condition -- if it is the result solely of excessive exercise. Recovery is usually uncomplicated, and the exercise-induced acidosis is self-correcting, according to Dr. Colin Tidy, writing for the physician website Patient UK. As the body takes in more oxygen, the production of acid is reduced and the acid/base balance is restored, usually without complications. If, however, there is another, underlying condition that is causing body fluids to accumulate acid, then follow-up treatment directed at that primary illness is essential.
References
- Patient UK: Lactic Acidosis
- University of Connecticut: Acid Base Online Tutorial
- "American Journal of Physiology: Regulatory, Integrative and Comparative Physiology": Biochemistry of Exercise-Induced Metabolic Acidosis; Robert A. Robergs et al.; September 2004
- SportScience.org: Exercise-Induced Metabolic Acidosis:
- "Journal of Applied Physiology": Point:Counterpoint: Lactic Acid Is/Is Not the Only Physicochemical Contributor to the Acidosis of Exercise; Dieter Böning and Norbert Maassen; February 2008
