The Lactic Acid Myth

One of the long-standing myths of sport and exercise is the demonization of “Lactic acid”. We have been told that is what makes your muscles burn and fatigue during exercise and we need to “flush it out” as part of the recovery process. It all sounds cool, but unfortunately NONE of that is true. 

What is it?

What is often termed as lactic acid is a byproduct of anaerobic metabolism, in which the body produces energy without using oxygen. “Actually your body doesn’t make “lactic acid” during exercise,” says Polly de Mille, registered clinical exercise physiologist and the director of sports performance at the Hospital for Special. “There’s none of it in your muscles or blood. The substance your body produces when you use carbs for energy is actually called lactate.”

Where did the myth come from?

Experiments done in the 1920s using frog legs showed that using electric pulses to make the legs contract produced lactic acid in the muscles, and that they stopped contracting after repeated stimulations — leading to the theory that lactic acid was responsible for muscle fatigue. But more modern research has shown that their findings apply to detached amphibian muscle but not to live mammals, including humans.

What about soreness?

Lactic acid is not related to exercise-induced delayed-onset muscle soreness. Research has also determined that lactic acid, also known as lactate, is actually an important fuel source for muscles and that the accumulation of lactate does not inhibit the ability of skeletal muscles to contract. Research suggests the soreness is a result of a cascade of physiological effects in response to microscopic trauma sustained during intense exercise. That cascade includes inflammation in the muscles in response to the microtrauma.

And what about “flushing it out?”

Even if you sat down and did nothing after a hard workout, your lactate levels would return to normal within thirty to sixty minutes. The right cool-down will help increase circulation and reduce the acidity that’s associated with (but not caused by) lactate. To jumpstart recovery, low intensity movement for 5 to 10 and up to 30 minutes immediately after exercise or on days you feel sore can speed up the process.