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Lactic Acidosis Related to Exercise

Lactic acidosis occurs naturally during vigorous exercise. Lactic acid, or lactate, is a by-product of metabolism that builds up in muscles and blood during strenuous activity. Lactic acidosis due to exercise is temporary and is not harmful. Serious medical conditions can also cause lactic acidosis, which can be dangerous in those situations.

Lactic Acidosis Causes

During exercise, muscles metabolize glucose (sugar) into energy. 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, a person’s 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. A person 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, through alternative chemical reactions. Lactic acid is produced and can rapidly build up in the blood and muscles.

Lactic Acidosis Symptoms

When a person's exercise intensity crosses the lactate threshold, the activity rapidly becomes much more difficult and unpleasant. Muscles ache and burn, the heart pounds, and a person feels starved for air. The muscles performing the exercise become extremely fatigued. These symptoms increase if a person continues to exercise above the lactate threshold. In a brief time, the person is physically unable to exercise any longer at that intensity.

Experts disagree as to whether it is lactic acidosis itself that causes these symptoms or if they result from other chemicals or processes that occur during vigorous exercise.

Lactic Acidosis Treatment

Lactic acidosis due to exercise is not harmful and no treatment is necessary. Natural processes make exercising above the lactate threshold impossible for more than brief periods.

Unlike lactic acidosis caused by serious medical conditions, no damage is occurring in the body during exercise. In fact, vigorous exercise that creates lactic acidosis can be a healthy part of an active lifestyle. Talk with your doctor to make sure you are ready for strenuous activity before starting this type of exercise program.

Other Types of Lactic Acidosis

Other types of lactic acidosis 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

These conditions cause lactic acidosis in an entirely different way than that of exercise. Lactic acidosis in these situations is usually diagnosed in a hospital, after a severe illness is already identified.

WebMD Medical Reference

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