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Muscle burn? Why Lactic Acid Isn’t Your Worst Nightmare

You’ve been pushing hard for the last hour. You have 30 more minutes to go, but your training partner is challenging you to a minute-long sprint. Not one to be perceived as a weakling, you accept their duel and push through. Your muscles scream as you push them faster, faster, faster. Eventually the burn gets so bad that you need to bring your body back down to an easy pace. “LACTIC ACID!” you curse.

As an endurance athlete, there has probably been at least one time that you’ve used the term “lactic acid” as a synonym for a swear word. But we often forget is that lactic acid is actually just a type of stored energy in your cells, and that with proper training and hydration you can delay that burn.

What Causes Muscle Burn?

Without dropping into graduate exercise physiology lingo, let’s talk about what exactly lactic acid is. While we think of calories, carbs, fat and protein as energy—our cells only care about one type of energy and that’s adenosine triphosphate (ATP). During exercise our body creates ATP from stored glycogen or consumed glucose. As long as you’re fueling correctly, at steady-state, your body will keep making ATP.

If you should decide to break out in an all-out sprint, your body doesn’t have the oxygen it needs to make ATP the normal route. So it changes metabolic paths. This new path produces lactic acid or lactate, and can only be sustained for 1 to 3 minutes. This is a protective mechanism your body has so that you eventually slow down enough to take in oxygen and restart normal metabolism. While lactic acid will create a burning sensation in your legs, it’s a necessary form of stored energy. Once your pace slows, your body is able to reconvert lactic acid into ATP fuel, and go back to business as usual.1

How to reduce muscle burn

While stored energy is good, the burn sure does hurt. We call the amount of lactic acid you can tolerate before ceasing movement the lactate threshold. The higher your lactate threshold, the longer you can perform at peak performance, and the stronger endurance athlete you are. Untrained athletes
could begin to accumulate lactic acid at 50-60% of maximal aerobic capacity, while trained athletes can push this number to 70-80%.2 Through VO2Max and Breath Training you can increase your lactate threshold.

You can also get the good (energy) without all the bad (burning pain) by staying well-hydrated. Hydrated athletes have more water to dilute the lactic acid and are more resistant to the pH change (hello burn). Focus on making sure you drink enough water and electrolytes before, during and after exercise.

By training efficiently, staying well hydrated you can improve your lactate threshold, reduce muscle burn and perform better.

There will always be weaknesses in your training to work on—your focus has to be on getting better through constant improvement. Head to to address your training weakness and be better.


1. Bernadot, D. (2012). Advanced Sports Nutrition. Human Kinetics. 2nd ed.
Ryan M. (2012) Sports Nutrition for Endurance Athletes. Velopress. 3rd edition
2. Ryan M. (2012) Sports Nutrition for Endurance Athletes. Velopress. 3rd edition


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