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Lactic Acidosis Related to Exercise

Lactic acidosis occurs naturally when lactic acid, a byproduct of metabolism, builds up in muscles and blood during vigorous exercise. Lactic acidosis due to exercise leads to muscle ache and fatigue, but is temporary and is usually not harmful.

Causes

When you exercise, your muscles metabolize glucose (sugar) into energy. Your muscles receive glucose continually through the blood, and also have their own stores of sugar (called glycogen).

Every person has an upper limit of exercise ability, called the anaerobic threshold or lactate threshold. The lactate threshold is basically a measurement of how fit the heart and blood vessels are. With regular exercise training, your lactate threshold goes up.

Exercising at an intensity level below the lactate threshold produces very little lactic acid, and the body quickly clears what is produced. You can exercise below the lactate threshold for a long time, even for hours.

Once the intensity of exercise exceeds the lactate threshold, muscles begin to use glucose inefficiently, and lactic acid can build up rapidly in the blood and muscles.

Symptoms

When you cross the lactate threshold, the activity rapidly becomes much more difficult and unpleasant. Muscles ache, burn, and become fatigued; the heart pounds; and you feel starved for air. These symptoms increase if you continue to exercise above the lactate threshold, and, in a brief time, you may be physically unable to exercise any longer at that intensity.

Treatment and Precautions

Lactic acidosis due to exercise typically doesn’t require any treatment. The kidneys and the liver usually can clear the extra lactic acid that accumulates from intense exercise. And natural processes make exercising above the lactate threshold impossible for more than brief periods.

More Serious Types

There are other types of lactic acidosis that can occur from side effects of drugs and serious medical conditions. These include:

•Severe infection (sepsis)

•Mitochondrial disorders

Carbon monoxide poisoning

•Loss of blood supply to a limb or other body part

•Shock

•Uncontrolled diabetes

•Severe kidney or liver disease

These conditions can be life-threatening and must be treated right away. Lactic acidosis in these situations is usually diagnosed in a hospital, after a severe illness is already identified.

WebMD Medical Reference

Reviewed by Melinda Ratini, DO, MS on May 25, 2013
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