Lactic Acid and Exercise: Understanding Lactic Acid Buildup

Also sometimes referred to as lactate, lactic acid is a byproduct of the human body’s cells producing energy without oxygen (also called anaerobic respiration). While the concentration of lactic acid does increase during strenuous exercise, it’s harmless and returns to normal levels once the body is able to rest. It is a common misconception that lactic acid causes muscle soreness or muscle fatigue during and after an intense workout, but in reality, delayed-onset muscle soreness (DOMS) is not caused by lactic acid buildup.

In the human body, lactic acid is produced mainly in red blood cells, brain cells, and muscle cells, forming when oxygen levels are low as your body uses carbohydrates for energy production—this includes periods of intense exercise as well as times when you have an infection or disease. The body even uses lactic acid to fuel some tissues, including the cardiac muscle (heart) and neurons. Lactic acid is also commercially produced and has applications in the food, medical, and construction industries.

The body produces lactic acid during high-intensity workouts like sprinting, powerlifting, and agility training. Essentially a waste product that is released into the bloodstream, lactic acid is a sign your muscles are switching to a quicker way to produce energy.

Normally, your body produces energy through processes involving aerobic respiration, which utilizes oxygen to turn food into energy. During this energy-producing process, called glycolysis, your muscle cells break down sugar (glucose) and convert it to energy in the form of adenosine triphosphate (ATP). The result is pyruvate, which the body can use to produce more energy but only if oxygen is present.

When your muscles are working hard during exercise, your muscles have to rely on an energy-producing process that doesn’t require oxygen (anaerobic respiration or anaerobic metabolism). As your muscles bypass the energy process that requires oxygen, they continue to use glycolysis to produce energy; meanwhile, your body begins to convert the unused pyruvate to lactic acid.

The buildup of lactic acid can cause a burning sensation in your muscles during your workout. Your liver and heart are responsible for processing lactic acid (the liver converts lactic acid back into sugar and the heart converts lactic acid into pyruvate), but during strenuous exercise these organs aren’t able to keep up with processing the lactic acid as quickly as your body is producing it.

While it is possible for lactic acid to build up to life-threatening levels (a condition called acute lactic acidosis), your body typically only reaches dangerous lactic acid levels because of acute illness or injury—not exercise. An underlying cause of heart attack, sepsis, cancer, or liver failure, for example, could result in your body’s tissues being deprived of blood and needing to go into anaerobic respiration, resulting in lactic acid buildup.

Symptoms of acute lactic acidosis include nausea, vomiting, and weakness. If these are concerns for you, they should be discussed with your physician, who can administer a blood test to measure your lactate levels.

While not inherently dangerous or unhealthy, the buildup of lactic acid can be uncomfortable. Though this should not be considered medical advice, here are six tips to reduce or prevent lactic acid buildup:

• Take breaks. Taking more breaks during high-intensity workouts can help oxygen return to your muscles, breaking up lactic acid buildup and potentially relieving some discomfort.
• Practice breathing. Breathing exercises may help deliver more oxygen to your muscles.
• Increase your endurance gradually. When starting new exercise routines, gradually increase the intensity and duration of the workout over time, allowing your body to get used to the routine as you gain strength and endurance.
• Maintain a balanced diet and stay hydrated. Maintaining a balanced diet and good hydration and eating a healthy meal before your workout (including foods high in potassium, fatty acids, and B vitamins) can help boost your energy levels.
• Try low-intensity exercise. A lower-intensity workout will enable your body to circulate enough oxygen to continue using aerobic respiration throughout the workout—resulting in less lactic acid being produced. Possibilities include brisk walking, light jogging, and yoga.
• Always warm up or stretch. Warming up your muscles and stretching before and after your workout can stimulate circulation, allowing more oxygen to flow to your muscles.

If you have a previous or pre-existing health condition, consult your physician before beginning an exercise program. Proper exercise technique is essential to ensure the safety and effectiveness of an exercise program, but you may need to modify each exercise to attain optimal results based on your individual needs. Always select a weight that allows you to have full control of your body throughout the movement. When performing any exercise, pay close attention to your body, and stop immediately if you note pain or discomfort.

In order to see continual progress and build body strength, incorporate proper warm-ups, rest, and nutrition into your exercise program. Your results will ultimately be based on your ability to adequately recover from your workouts. Rest for 24 to 48 hours before training the same muscle groups to allow sufficient recovery.

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