The myths that massage therapy can help you get rid of lactic acid or lactate and that they are “toxins” are still prevalent among massage therapy culture. Among fitness professionals, this is also no exception since many believe that lactate or lactic acid is a primary cause of muscle soreness due to the “burn” you get after a workout. Contrary to this popular belief, lactate actually reduces or buffers the rate of acidosis build-up and is not a contributor to acidosis and muscle soreness.
Lactate is produced in all organs in your body, with your liver and kidneys being the top two producers when you are at rest. During exercise, skeletal muscles are the largest manufacturers of lactate as a result of breaking down glucose for energy, especially during high-intensity, short-duration exercise like sprinting and Olympic lifting.
When adenosine triphophate (ATP) is used for energy, it converts to adenosine diphosphate (ADP) with a released proton, which has a positive charge. When there is enough oxygen to meet muscle contraction demands, no proton is accumulated in excess within the cell since the extra protons in the cells’ cytosol get shuttled into the mitochondria. Theoretically, the accumulation of protons is thought to cause acidosis, but this idea contradicts what research says.
“The term lactic acid and pyruvic acid arise from research and studies published more than 100 years ago,” said Dr. Michael Lindinger, who taught at the University of Guelph for 25 years. “At the time, the understanding of biochemistry was in its infancy, and the physical and chemical properties of lactic acid and pyruvic acid in the body in living cells was poorly understood. All of the early research was conducted using dead or dying muscles.”
Lindinger said that academics and clinicians use the terms lactic acid and lactate as if they’re the same things (same with pyruvate and pyruvic acid). Back then — and probably now — it was a way for researchers to make physiology easier for the public to understand.
“Everybody has heard of lactic acid, but not everyone has heard of lactate,” Lindinger said. He described lactic acid and pyruvic acid as dissociated compounds, which means they are broken apart on a molecular level to form an acid (+) and base (-). But this form is uncommon because it’s unstable. Thus, lactic acid and pyruvic acid exist in your body as lactate and pyruvate.
Does lactic acid cause muscle acidosis?
The short answer is no, but that doesn’t explain why lactic acid or lactate doesn’t cause muscle acidosis. Typical physiology textbooks often depict the extra proton accumulation in glucose metabolism to be responsible for muscle acidosis. But what looks ideal in a math equation does not necessarily reflect what actually happens in our body.
Lindinger said that scientists can count the number of protons mathematically in metabolic reactions or take measurements of the pH level. But both methods are incomplete because scientists have not accounted much of the roles of water in biochemical systems, which makes the process more complex than on paper.
“Acidosis is therefore best understood not by dissecting a series of individual reactions, but by examining all of the biochemical, chemical and physical processes that occur simultaneously,” Lindinger said. “Trying to do this is very complex, so the natural inclination is to simplify — and in the process — describe the situation incorrectly or, at best, poorly.”
Lindinger referenced that the outdated idea that acidosis from lactic acid accumulation is a direct cause of fatigue at normal body temperature came from studies on frog muscle conducted at low temperatures. This doesn’t translate well to living, warm bodies. Newer research also finds that acidosis contributes to allosteric regulation, which is where enzymes change their shape to fit into a molecule, like a protein. This process increases or slows the rate of some enzyme reactions.
“The best answer we currently have for what contributes to acidosis in contracting muscle still comes from using the physico-chemical approach,” Lindinger said. “What does matter is that muscles do become acidotic with increased activity, and so do our bodies. Acidosis has been given a very negative association over 150 years of scientific study, beginning with Berzelius reporting lactic acid in muscles (dead or dying) from hunted stags.”
Lindinger also added some newish findings about lactate:
- Lactate is not an end product or waste product) of metabolism
- Lactate has now been shown to be able to directly enter the mitochondria – it does not first have to be converted to pyruvate (George Brooks)
- Lactate does not cause fatigue (many people)
- Lactate does not cause pain (Saltin has performed lactate infusion experiments, as have we (with Brooks)
- Lactate is a preferred fuel source (compared to glucose, fatty acids, amino acids) by all known cells of the body – cells readily take up lactate from the blood and use it to produce ATP oxidatively (by the mitochondria) (Brooks with us)
- Increased lactate at the muscle cell membrane is beneficial for maintain sarcolemmal excitability (Nielsen)
What can be done to change the lactic acid narrative?
So despite decades of research, replicated studies, and publications about lactate, many universities and colleges still teach what was found a century ago. This information gets passed on to patients, the public, and the media, which continues the lactic acid myth cycle. The primary problem comes from how physiology is taught.
But Lindinger is optimistic that this piece of the metabolic puzzle can be corrected.
“I believe that big changes in how this will be taught are yet to come,” he said. He referred to the work and teachings of physiologist George Brooks at the University of California Berkeley, who has been at the forefront of lactate-related research for about 60 years.
“[He] has published a series of excellent reviews in the past six years. It will take time for this, and the mechanistic research of his group and others to become mainstream,” Lindinger said.
In some ways, the outdated yet popular lactic acid narrative is as problematic for exercise scientists as many massage therapy myths to manual therapists, such as sweating can remove “toxins” from your body.
“Old habits are hard to break,” Lindinger said. “We need to have the newer generation of scientists who take the time to read the primary literature and apply this to their teaching.
“Sadly, most university teaching is still performed from textbooks, which are notorious for being outdated. This worked 100 years ago when the rate of knowledge increase was much slower than today. Textbooks should no longer be used at the college and university level.”