Are you feeling the burn? No; this isn’t going to be a political ad; “feeling the Bern” isn’t quite what we’re discussing here today. This isn’t about politics but rather basic biochemistry, often misunderstood, often mistaught, and affects every person who exercises, loves someone who exercises, or has a patient who exercises.
Nearly everyone’s heard that high-intensity resistance training, distance running, and other forms of intense physical activity create a surplus of lactic acid which builds up in our muscle tissues and causes us to experience that familiar burning sensation.
While there is no denying that exercising intensely causes a feeling like our muscle fibers are on fire, the cause for this phenomenon turns out to be something entirely different than lactic acid, as you have likely been informed. This is nothing more than a health fallacy.
The lactic acid theory is not new; in fact, it was two 1922 Nobel Prize recipients, Otto Meyerhoff and Archibald V. Hill, who put forth the theory that lactic acid was the culprit.
Having a Nobel Prize in carbohydrate metabolism in skeletal muscle, it seemed like they would have a good guess. And it was; until recently when it was proven that lactic acid is not the causative factor, nearly everyone believed this to be true.
In their groundbreaking meta-study, Robergs, R.A., Ghiasvand, F., & Parker, D. (2004). Biochemistry of exercise-induced metabolic acidosis. American Journal of Physiology: Regulatory, Integrative and Comparative Physiology. 287: R502-R516, the authors proposed that the preponderance of evidence points to a rather different cause for the sensation of muscle burn: excess protons.
While fitness trainers, nurses, and doctors everywhere continue to tell patients about lactic acid and “the burn”, the truth has quietly been spreading for the last ten plus years. “Lactic Acidosis”, after all, is standard fare in the course work of health care professionals, and not everyone has received the update that the theory is defunct.
Carl Whilhelm Sheele, a Swedish chemist who lived in the 18th century, first discovered lactic acid. It was first isolated in samples of soured milk, and so the moniker “lactic” was appropriate, as it denotes an association with milk and dairy products. By 1922, the understanding of the two Nobel Laureates was that lactic acid was a reaction to the glycolysis reaction, the splitting of sugar for energy, in the absence of oxygen, or anaerobic conditions.
This theory seemed smart. It made sense. It fit with the observable phenomena. But nevertheless, it was completed without factual basis. While lactic acid does build up in overused muscles, it is not the causes of acidosis, but rather the result.
It turns out that acidosis in muscles is caused by an excess of free protons in the cells and tissues. Interestingly, it isn’t an organic compound or complex substance. While protons cannot be seen, they can be easily measured.
If you have recently taken biochemistry, or if you’re a serious health professional, you’ll recall that a free hydrogen ion is a proton. ATP, when hydrolyzed by a water molecule, is split into ADP and phosphate. A by-product is the release of a single hydrogen ion.
As you may recall, pH is the measure of the number of free hydrogen ions in a solution, or mixture of liquid. At a lower pH, there are more free hydrogen atoms. This is what makes such a liquid acidic. When the pH is higher, there are fewer free hydrogen ions. This means it’s more basic.
So where’s the lactate from, anyway? Fitness therapists, nurses, physicians of all types, and injury recovery specialists will already be scoffing, ready to pull out their dusty books from university. Hold on. Before you waste the effort lifting a book, Robergs, Ghiasvand, and Parker have a response. In their 2004 study, they cite the accumulation of lactate as the result of free pyruvate and protons from glycolysis of carbohydrates joining, each pyruvate molecule linking with precisely two free protons.
Thus, the creation of lactate is the body’s way of attempting to raise tissue pH, by mopping up the free hydrogen ions created from vigorous muscle exercise. The body does not create lactic acid in this reaction, but rather lactate. Lactic acid releases hydrogen ions at pH of less than neutral by definition. Once this ion is lost, the lactic compound can then link with a sodium or potassium ion to form an avid salt. Roberts et al. (2004) details this reaction for those whose interest has been piqued by this article. Click here
So when you return to the clinic and your colleagues begin ranting about lactic acid build-up, quietly and calmly direct them to the Roberts study. Its’ already twelve years and the myth of lactic acidosis just won’t end. Does it really matter one way or another?
For all practical purposes, health care professionals will continue helping patients as they had before. But new knowledge, elucidation of vague half-truths, and discovery should always be welcome.
This is especially true for health care providers who routinely explain biophysical phenomena to patients, and wish to be as precise and accurate as is possible. If you want to go on believing in a now-disproven lactic acid theory and you aren’t inflicting your erroneous belief on others, it’s not quite the same.
(C) H Miller, Dee Albin, NJMassage.Info