What is lactic acid?

Even at the highest levels there are myths that are perpetuated, especially when it comes to muscle recovery and what causes muscle soreness. As athletes, we’re typically told that lactic acid is produced by muscles during intense exercise and a buildup of it causes muscle fatigue and is the culprit for muscle soreness after a long run or hard work out. This theory has gone unquestioned for more than 80 years after lactic acid was first linked to exercise metabolism in the 1920s.  So what is the truth about lactic acid that has been getting a bad rap for years?

Myth #1) “The burn” is caused by lactic acid

We’ve all heard the term “feel the burn” and until recently, it was thought that the burning sensation during a heavy lifting session or fast sprint was caused by lactic acid buildup in the muscles. What’s actually happening when we exercise is as our body breaks down ATP for energy, hydrogen ions are released. When oxygen to our muscles is limited, our body can’t keep up with breaking down the hydrogen ions fast enough. The buildup of hydrogen ions makes the environment acidic causing our muscles to burn.

To clear things up even more (or make them more confusing) lactic acid doesn’t actually build up from a technical standpoint but lactate does. As exercise intensity increases, our bodies rely on glucose to keep up with the demand for energy. Pyruvate (an end product of broken down glucose) molecules begin to build up along with the hydrogen ions. The pyruvate absorbs two hydrogen ions and forms lactate. We know now that lactate actually acts as a buffer to the acidic hydrogen ions and without it, the accumulation of hydrogen ions would cause “mechanical failure” in our muscles.

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Myth #2) Lactic acid is waste and causes muscle fatigue

Lactic acid was thought to be a dead-end waste product produced in the muscles during activity. Research actually indicates that our bodies reuse lactate as a source of energy for our muscles. It’s estimated that roughly 75% of lactate produced inside the muscle cells is recycled into glucose and used as fuel. Definitely not all waste…

Lactate actually helps delay muscle fatigue rather than cause it. During long runs, your muscles lose power by becoming depolarized. The accumulation of lactate in muscle tissue helps to partly counteract the effect of depolarization.

(You might like this article about the importance of training your fast-twitch muscle)

Myth #3) Lactic acid causes muscle soreness

Lactate actually clears out of your system 30-minutes to one-hour after working out and the majority is recycled and turned into energy. Delayed onset muscle soreness (or DOMs) is actually the result of microtrauma in the muscles and connective tissues, causing inflammation. Most exercise can induce some sort of soreness but exercise with a greater emphasis on the lengthening or stretching phase plays the most significant role in how sore you get the day or two after a hard workout. 

If you are prone to DOMS or pain in general, check out these helpful tools to improve your muscle recovery. 

Trying to dispel an 80-year-old myth will take some work, but over the last couple of years and thanks to more research, lactic acid has finally started to get the positive credit it deserves.