Written by Evelyn Calado, MKin, CSCS, RKin
You’ve probably heard it before—“My legs are full of lactic acid,” or “It’s the lactic acid that makes me sore.”
But here’s the truth: lactic acid isn’t to blame for muscle soreness or fatigue—and in fact, it’s not even the enemy. It’s time to clear this up once and for all.
What Actually Happens During Exercise?
When you train—especially at moderate to high intensities—your body breaks down carbohydrates to produce energy. This process is called glycolysis, and it produces two main byproducts:
Pyruvate, which can be used to produce energy
Hydrogen ions (H⁺), which increase acidity in the muscle
Here’s the key thing to understand:
Hydrogen ions make your muscles feel acidic—not lactate.
As hydrogen ions build up, they lower the pH in the muscle (pH is a scale that measures how acidic or basic something is—lower pH means more acidic). This increased acidity can interfere with how your muscles contract and lead to that familiar burning sensation during hard efforts.
So What Is Lactate?
Lactate (often confused with “lactic acid”) is actually a helpful byproduct, not a waste product. When the rate of glycolysis increases and hydrogen ions start to accumulate, lactate is formed when pyruvate binds with those hydrogen ions.
This is a good thing. Lactate formation actually helps buffer the acidity by mopping up excess hydrogen ions. This slows down the drop in pH and helps you keep going longer.
So instead of being the villain, lactate is your body’s way of protecting itself from fatigue.
Myth-Busting: Lactate ≠ Muscle Soreness
Muscle soreness, especially the kind that shows up 24–48 hours later, is known as DOMS (Delayed Onset Muscle Soreness). It’s caused by microdamage to muscle tissue, inflammation, and the repair process—not by lactate.
The lactate-muscle soreness myth was debunked decades ago. Yet it continues to live on in gym talk, group classes, and even outdated training certifications.
We Produce Lactate All the Time
Contrary to popular belief, lactate isn’t just made during intense training. Your body is constantly producing and clearing lactate—even at rest.
It’s used as:
A fuel by the heart, brain, and slow-twitch muscle fibers
A precursor to glucose in the liver through the Cori cycle
A signaling molecule for adaptation and recovery
Far from being a waste product, lactate is essential to energy production and endurance performance.
Why Lactate Threshold Matters
Your lactate threshold refers to the highest intensity at which your body can produce and clear lactate at the same rate. Once you exceed that threshold, lactate begins to accumulate—but not because it’s causing fatigue. It’s a sign that your body is working hard and relying more on anaerobic metabolism.
What matters is that:
Lactate is a proxy for effort, not the cause of failure
The better trained you are, the more efficiently you can clear lactate, which allows you to sustain high output for longer
This is why aerobic base training and well-planned intervals are so valuable—they help improve your body’s ability to manage lactate and stay out of deep fatigue.
The Bottom Line
MythRealityLactic acid causes sorenessMuscle soreness comes from tissue damage, not lactateLactate makes you fatigueLactate buffers fatigue and helps you continueLactate is a waste productIt’s a valuable fuel and performance toolHigh lactate = badIt reflects effort—not failure
So next time you feel the burn or hear someone say “it’s the lactic acid,” you’ll know better: Lactate isn’t making you slow down—it’s helping you stay in the game.
Train. Play. Repeat.
Want to learn how to build your aerobic base, improve lactate clearance, and train smarter—not just harder? Book a session at Avos Strength and we’ll break it down.
