You may have heard the terms “lactic acid” and “lactate” with your personal trainer or massage therapist if you are talking about muscle soreness and exercise, and they are often used interchangeably as if they are the same things. However, the minor differences between them are important when discussing how they play a role in metabolism.

The major difference between lactate and lactic acid is one proton in the molecule. All acids have a positive charge (+), indicating that it is a hydrogen ion donor (H+). The conjugate base is lactate, which has a negative charge (-). So, lactic acid is not something your body produces or removes from your muscles. (1) Instead, lactate should be used when discussing the metabolic process.

lactic acid to lactate

Image: Nick Ng

Most of the time, you are in an aerobic state, where you body gets enough oxygen to carry out its normal functions. This usually occurs when you are walking or jogging as long as you are not in a state of oxygen deficit. Even if you are sitting at a cafe and reading this article, you are still in an aerobic state.

However, when are you sprinting away from an angry mountain lion or swinging heavy kettlebells at the gym, your body needs a quicker method to produce energy: enter glycolysis. Unlike the aerobic route which requires oxygen, glycolysis does not need oxygen to produce energy. It relies almost entirely on carbohydrates (glucose) to produce energy, and it is a quicker energy manufacturer than aerobic metabolism.

In aerobic and anaerobic metabolism, your body breaks down glucose into a byproduct called pyruvate through a chain reaction of steps. When the amount of oxygen you get into your muscles meets your body’s demand, pyruvate is sent to your muscle cells’ mitochrondria where it gets processed for more energy. If you do not get enough oxygen, your body uses glycolysis as a short cut to produce energy by turning pyruvate into lactate. Under this process, you can only sustain high-intensity exercises for a short period of time—about 30 seconds to three minutes—before you start to feel “the burn” and your muscles fatigue, refusing to do another rep or endure another second.

This happens because of the lactate accumulation in your muscles, which increases the acidity in your blood by lowering its pH level. Dr. Stephen Roth, who is the Director of Public Health Sciences at the University of Maryland, mentioned in Scientific American that this is your body’s way to “prevent permanent damage during extreme exertion” by slowing down the muscle contraction.

“Once the body slows down, oxygen becomes available and lactate reverts back to pyruvate, allowing continued aerobic metabolism and energy for the body’s recovery from the strenuous event,” he wrote.

This pretty much dispels the common belief that massage therapy can “remove” lactic acid or lactate from your muscles.

References

1. Robergs RA, Ghiasvand F, Parker D. Biochemistry of exercise-induced metabolic acidosis. 2004 Sep;287(3):R502-16.

2. Roth S. Why Does Lactic Acid Build Up in Muscles? And Why Does It Cause Soreness? Scientific American. 2006 Jan 23.

 

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A native of San Diego for nearly 40 years, Nick Ng is the founder and editor of Massage & Fitness Magazine, an online publication for curious massage therapists and the public who want to explore the science behind touch, pain, and exercise, and how to apply that in their hands-on practice or daily lives.

An alumni from San Diego State University with a B.A. in Graphic Communications, Nick also completed his massage therapy training at International Professional School of Bodywork in San Diego in 2014. Prior to entering the massage profession, he also had worked as a personal trainer for 14 years.