The Myth of Lactic Acid

Lactate

Why everyone seems to attribute muscle soreness to lactic acid is beyond me. Lactic acid does not cause the burn. It does not cause soreness. It is not a waste product. We've known these things for decades, but somehow these misunderstandings refuses to die.

Let's discuss what's actually happening. At rest, the aerobic system covers energy demand. When demand outpaces what oxygen can fund, the glycolytic system steps in. It breaks down blood glucose and muscle glycogen to produce ATP. Lactic acid is formed in this process, but it's quickly broken down into hydrogen ions and the often, but inappropriately, maligned byproduct known as lactate.

Lactate is fuel. George Brooks mapped the lactate shuttle decades ago — once formed, lactate moves to tissues that can use it, where it converts back to pyruvate and feeds the Krebs cycle. Cardiac tissue and type I fibers run on it. The body produces lactate not to punish the athlete but to keep the work going.

The Burn

The burning sensation is the accumulation of the aforementioned hydrogen ions. When glycolysis runs anaerobically, hydrogen ions build up alongside lactate. Blood pH drops. The muscles complain. Lactate gets blamed because it shows up at the same party. Guilt by association.

The Soreness

DOMS is muscle damage. Microtrauma, repair, inflammation. It has nothing to do with lactate sitting in the tissue two days later — lactate clears fast. The soreness people attribute to "lactic acid buildup" is the muscle remodeling in response to load.

Why It Matters

The glycolytic system is an intermediary. It bridges aerobic and alactic work. It extends high-intensity output past what oxygen alone can fund. It fuels the very tissues coaches assume it's poisoning.

This is the engine behind speed endurance and special endurance. Train it accordingly. Stop blaming the byproduct.

-Schmidt