"Lactic Acid"/Lactate Myths and "Myth Busts"

Training Q&A [Moderated]
1

Hi,

I came across this youtube video by “Shredded Sports Science” on lactic acid/lactate and the myth that it causes the “burn” during anaerobic-glycolytic exercise:

He basically states that it is not a buildup of lactate but rather an accumulation of protons (removed from lactate), which lowers pH in the muscle, causing acute fatigue. Through a cursory google search I found an article which contradicts this claim: http://running.competitor.com/2010/01/training/the-lactic-acid-myths_7938

Here is the most relevant section:

"How exactly did lactate buildup cause the muscles to fatigue? Biochemists believed that lactate was formed in the body by the removal of a proton from lactic acid. When protons accumulate in living tissues, these tissues become more acidic. And when muscles become too acidic, they lose their ability to contract.

"This tidy little explanation began to unravel in 1977, when South African biochemist Wieland Gevers showed that the reaction producing lactate actually consumes a pair of free protons, thus retarding muscular acidosis rather than promoting it. Much more recently, scientists have observed that while protons do indeed accumulate in the muscles during high-intensity exercise, increasing muscle acidity, these protons are produced through a reaction that is completely separate from that which produces lactate.

“To make matters even worse for supporters of the classic lactate hypothesis, we now know not only that lactate does not cause muscular acidosis, but also that the muscles never reach a level of acidity that would directly cause dysfunction (or fatigue) of the muscle fibers anyway. The body’s normal pH at rest is approximately 7.4. During intense exercise, as the muscles become more acidic, pH may drop as low as 7.0 at the point of exhaustion. However, when muscle cells are electrically stimulated outside the body, mechanical failure only occurs when the pH drops all the way down to 6.8. This observation suggests that fatigue always occurs before a catastrophic loss of acid-base homeostasis in the muscles takes place.”

No studies are referenced in the article. Just curious what the doctors think about all this. Thanks!

2

Yea I think we have talked about all this before in various podcasts. The most relevant points:

  1. Lactic acid doesn’t really exist with respect to muscle physiology. It’s lactate and hydrogen ions (protons). Accumulation of hydrogen ions cause localized acidity and lactate acts as a buffer, which later gets shuttled to the liver to participate in the Cori cycle to make pyruvate and ultimately glucose.

  2. There is a central governor or similar of “fatigue” that pumps the brakes on performance well before bad things happen. The brain, which is the “central” portion of the central governor model, takes into consideration peripheral fatigue determinants (accumulating products and depleted products), central fatigue (neurotransmitter changes as well as psychological factors including expectations of performance, danger, injury, environmental factors, etc.), and muscle damage to determine your performance.

  3. The pain experience secondary to acute training fatigue is much more complex than “acid buildup”