Intense Exercise & Metabolic Acidosis

Under normal conditions, your body's acid-base balance is slightly on the alkaline side of neutral and is reflected by a pH level of approximately 7.4. Many factors can lead to an increased level of acid in the body, a condition known as acidosis, which can bring the pH of your blood and body fluids closer to, or below, neutral on the pH scale. Intense exercise is a trigger that can lead to acidosis.

Metabolic Causes of Acidosis

The acidification of your body's internal fluids can result from a number of internal processes. Included among these are factors that increase the body's metabolic production of acids or decrease the body's production of acid neutralizing bases. When acidosis is caused by disturbances of normal biochemical or physiological pathways, it is referred to as metabolic acidosis.

Muscle Contraction and Acidosis

Muscle contraction is fueled by a molecule known as ATP, which is metabolically produced in the body by one of two chemical pathways. In the presence of sufficient amounts of oxygen, ATP for muscle contraction is produced aerobically and does not lead to acidosis. As muscle contractions increase in their intensity, the need for ATP may outstrip the ability of oxygen-supported aerobic metabolism to supply ATP, and your muscles will switch to an anaerobic ATP pathway. This anaerobically fueled ATP production produces lactic acid, which can acidify your body's fluids and result in metabolic acidosis.

Respiratory Function and Acidosis

Intense exercise using the aerobic energy supplying pathway produces carbon dioxide as a byproduct that is carried by the blood to your lungs, where it is expelled as you breathe out. As exercise intensity increases, carbon dioxide levels in the blood will increase, particularly if your respiratory capacity cannot expel carbon dioxide fast enough. As carbon dioxide levels build up in your blood, it creates the chemical carbonic acid, which will lower the pH of your blood and body fluids, causing metabolic acidosis.

Dealing with Metabolic Acidosis

The onset of metabolic acidosis during intense exercise can be limited if your aerobic energy supply system has been adequately trained, thereby delaying the need to shift to the acid-producing anaerobic pathway. A well-conditioned respiratory system, capable of eliminating large amounts of carbon dioxide, will also help control metabolic acidosis. Aerobic endurance training can help to improve both of these systems.