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 usually not harmful; it may be dangerous if it results from a serious medical condition.
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 usually 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, the kidneys and the liver usually can clear the extra lactic acid that accumulates from vigorous exercise.
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
- 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.