Lactic Acid Breakdown in Workouts

Lactic acid is a byproduct of metabolizing carbohydrates anaerobically, or without oxygen, which occurs during high intensity workouts. During your workout, lactic acid can be broken down to provide energy for muscles and other organs, such as your heart. Lactic acid is also converted into blood glucose, or blood sugar, as well as amino acids, the building blocks of proteins.

  1. Lactic Acid Production

    • Muscle cells break down carbohydrates to produce energy in a multi-step process called glycolysis. The end result of glycolysis is a compound called pyruvate. If oxygen is available, pyruvate can be metabolized aerobically to produce additional energy. However, if your circulatory system is unable to supply oxygen quickly enough to your muscles, such as during very vigorous exercise, pyruvate is converted to lactic acid. This conversion allows glycolysis to continue anaerobically.

    Lactate Metabolism

    • During high intensity exercise, lactic acid can accumulate in your muscles and bloodstream as lactate. Although high lactate levels are associated with muscular fatigue, lactate itself does not cause fatigue. In fact, lactate is an important energy source for muscles, both during and after exercise. Lactate is shuttled from fast-twitch muscle fibers, which rely heavily on anaerobic metabolism, to slow-twitch muscle fibers, which primarily utilize aerobic metabolism, where it can be oxidized to produce energy.

    Other Breakdown Mechanisms

    • Other tissues in your body also metabolize lactate for energy. During strenuous exercise, lactate becomes a primary fuel for your heart. Your liver converts lactate into glucose, some of which it stores as glycogen after your workout. Muscle cells also convert and store lactate as glycogen. In addition, your muscle cells can convert lactate into amino acids, particularly the amino acid alanine, in a process called transamination. In turn, your liver can convert alanine into glucose to be used for energy. A small amount of lactate is also removed in your sweat as you work out.

    Workout Considerations

    • Lactate is removed from the bloodstream fairly quickly, with about half of the accumulated amount cleared within 15 to 25 minutes after a workout. Actively cooling down after a vigorous workout will remove lactate from your bloodstream more quickly than simply resting. This active recovery can include activities such as walking, light jogging or calisthenics. Increased blood flow seems to account for the faster lactate clearance. However, don't make your cool-down too vigorous. Doing so can promote the production of more lactate.