How to reduce lactic acid build up in your muscles during exercise — and why it happens

• Lactic acid is a byproduct of intense exercise that causes a burning sensation in your muscles.
• A lactic acid build-up in your muscles may cause soreness while you are exercising, but it will not contribute to muscle soreness after a workout.
• To reduce lactic acid build-up during your workouts, you can take more frequent breaks or decrease your exercise intensity.
• This article was medically reviewed by Jason R. McKnight, MD, MS, a family medicine physician and clinical assistant professor at Texas A&M College of Medicine.

Contrary to popular belief, lactic acid is not responsible for sore muscles after an intense workout. However, it is responsible for that burning sensation you experience when exercising.

Here's what you should know about lactic acid build-up in your muscles, and how to reduce it.

What is lactic acid?

During high-intensity workouts, your body produces a byproduct called lactic acid, or lactate.

"When someone is doing a lot of high-intensity exercises, it leads to a build-up of lactic acid in the muscle, which is then moved into the bloodstream," says Jessica Garay, PhD, RDN, FAND, an assistant professor in the Department of Nutrition and Food Studies at Syracuse University.

Some examples of high-intensity exercises that produce lactic acid include:

• Sprinting
• Powerlifting
• Agility training

What causes lactic acid build-up?

When you are working out intensely, your body undergoes many biochemical processes to keep you energized. Normally, your body produces energy through aerobic respiration — a process that relies on oxygen to turn food into fuel.

However, when you are exercising intensely, your muscles require more oxygen than you can breathe in. Therefore, your muscles begin to rely on anaerobic respiration — an energy-producing process that does not require oxygen. Lactic acid is a byproduct of this process.

"This is actually a really good thing because lactate can act as a buffer and decrease the acidity in your muscles," says Audrey Stone, PhD, an assistant professor in the Department of Kinesiology and Health Education at the University of Texas.

Symptoms of lactic acid build-up

When lactic acid builds up in your muscles, it causes a burning sensation. Usually, you'll feel this during the middle to end of your workout because this is when the buildup will be the greatest.

This happens during longer and more intense workouts because lactic acid is produced at a faster rate than your body is able to remove it. As soon as you rest, or decrease your exercise intensity, your lactic acid levels will return to normal and the burning sensation should go away.

"Our bodies are actually pretty resourceful at dealing with a build-up of lactic acid," says Garay.

However, some people may be at risk for lactic acidosis, a condition that causes lactic acid to build-up in the bloodstream. Most lactic acid moves through the bloodstream to the liver where it is broken down — but people with liver problems are not able to do this as effectively when exercising.

Symptoms of lactic acidosis include:

• Nausea
• Vomiting
• Weakness

Other groups of people that are at risk for lactic acidosis include those with conditions that cause low blood pressure and too little oxygen flow to tissues. These include:

• Cancer
• AIDS
• Alcoholism
• Cirrhosis

To treat lactic acidosis, you should seek medical attention immediately, as your doctor can determine how to address the underlying cause.

Lactic acid vs. delayed onset muscle soreness

Lactic acid is often blamed for soreness after a workout, when in fact, this is caused by delayed onset muscle soreness — also known as DOMS.

"Usually when people come to and ask how to get rid of lactic acid build-up, they are really talking about DOMS," says Stone.

DOMS refers to muscle pain that develops one to three days after strenuous exercise. The soreness you feel is inflammation caused by normal damage to your muscle fibers during a hard workout.

"Lactic acid buildup is not the cause of DOMS, though it may simultaneously occur within the same workout that ultimately produces DOMS," says Garay.

There are a few key difference between DOMS and lactic acid build-up:

How to reduce lactic acid build-up

Lactic acid production is not unhealthy, but it can be uncomfortable. Here are some tips to help you prevent lactic acid buildup and reduce discomfort during a workout.

• Take a break: If you are doing a high-intensity workout, taking breaks can help oxygen return to your muscles and break up lactic acid build-up. This will relieve some of the pain you may be experiencing. "Once you stop exercising at such a high intensity, your body starts breaking down the lactic acid pretty quickly," says Stone. To finish your workout strong, take a few short breaks if you start breathing heavily or if you are experiencing a lot of burning in your muscles.
• Reduce your exercise intensity: If you are exercising at a lower intensity, your body will have enough oxygen to use aerobic respiration throughout the workout. This means less lactic acid will be produced. Some examples of low-intensity exercises include briskly walking, light jogging, or yoga.

The bottom line

Lactic acid production is a normal response to high-intensity exercise. Although working out can sometimes be uncomfortable, it shouldn't be painful. If you are experiencing intense burning from lactic acid buildup, take breaks or change up your exercise routine.

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