What is Lactic Acid?

by Andy Van Grinsven

You know that feeling you get during a set of high-repetition squats or a 400-meter sprint? The one that feels like your veins are pumping gasoline and someone lit a match? You can thank lactic acid, the proverbial boogeyman of fitness and scapegoat for everything from searing pain to muscle soreness to a poor FICO score (Okay, maybe pay those bills on time). Nonetheless, lactic acid has played a role in every single one of your fitness endeavors. Right now, in fact, your body may be producing it and you don’t even know it! So what is lactic acid (LA), what does it do, and is it deserving of the bad reputation it’s accumulated over the years?


Lactic acid, or rather, lactate, is a byproduct of anaerobic metabolism. Your body requires ATP or the “energy currency” needed for muscles to contract and do physical work. Through a process called glycolysis, cells break down stored glucose into one of two things; pyruvate or lactate. Depending on what you’re doing at the moment, your body is probably producing and removing lactate at a steady pace in order to keep the body balanced.


During aerobic metabolism, and with adequate oxygen in the system, pyruvate is shuttled off to be further broken down in order to produce more ATP. However, during the first one to three minutes of exercise or during high-intensity bouts like sprinting or heavy weight training, there isn’t enough oxygen being delivered to the working muscles and glucose ends up as lactate. If conditions do not change and your breathing and oxygen levels do not increase fast enough to match intensity, a buildup of lactate in the muscles occurs, blood acidity increases, and you begin to feel the burn as performance fades. As you crash to the floor or drop the bar, you just might curse LA for bringing the #GainTrain to a screeching halt. But you’d be wrong.


Believe it or not, this lactate and acidity accumulation is a protective mechanism. Increased acidity negatively influences muscle contractibility, putting the hypothetical brakes on you and your workout and prevents catastrophic muscle damage.

Notice the heavy breathing while you recover? As you inhale and exhale, finding the furthest depths of your lungs, you introduce oxygen and buffer lactate, removing it and restoring pH balance to your body as it works to extinguish the burning flame.


But what about the soreness you’re dreading tomorrow or the next day? By then, lactate has been removed and metabolized, therefore, we can no longer point the blame finger at lactic acid. Instead, that Delayed Onset Muscle Soreness, better known as DOMS, can be attributed to micro-trauma at the muscle-cell level. This is an inflammatory response to simply repair muscle tissue and adapt to current stress levels, allowing you to perform or even outperform your previous exercise session.


Through consistent training, you can improve your body’s response to producing and removing lactate. Or even better, shift the threshold at which accumulation exceeds removal and exercise cessation is imminent. In the meantime, while you’re enjoying your last few reps, sled drag, or sprint intervals on the devil’s tricycle (Airdyne bike), remember this; the body is incredibly fascinating and able to endure, adapt, and overcome stresses so that you become stronger, faster, and more jacked (maybe even tanner) than before. But in all seriousness, take a moment to admire the infinitely complex systems at play while your heart pumps and your muscles burn and your lungs can’t keep up. Lactic acid is simply along for the ride and meant to keep you out of harm’s way.

So in conclusion, if we are judging lactic acid as a friend or foe, we should really be working to make it our best friend.

NFM Staff
Author: NFM Staff

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