Everything you have ever been taught about lactic acid (or lactate) is wrong. Of course everyone has heard something along the following lines:
"Lactic acid is what builds up in your muscles. It is what makes your muscles burn. Its build-up is what makes your muscles tire and give out."
Coaches and personal trainers tell athletes and exercisers that they have to learn to work out at just below their "lactic threshold," that point of diminishing returns when lactic acid starts to accumulate. Some athletes even have blood tests to find their personal lactic thresholds.
These ideas are all wrong. Lactic acid is actually a fuel, not a caustic waste product as advertised. Muscles make it deliberately, producing it from glucose, and they burn it to obtain energy. The reason trained athletes can perform so hard for so long is because their intense training causes their muscles to adapt so they more readily and efficiently use lactate as a fuel.
The notion that lactic acid was bad took hold more than a century ago, and the meme stuck because it seemed to make so much sense. Its origins lie in a study by a Nobel Laureate, Otto Meyerhof. In the early years of the 20th century, he cut a frog in half and put its bottom half in a jar. The frog's muscles had no circulation and no source of oxygen or energy.
Dr. Meyerhof gave the frog's leg electric shocks to make the muscles contract, but after a few twitches, the muscles stopped moving. When Dr. Meyerhof examined the muscles, he discovered that they were saturated in lactic acid.
A theory was born - a lack of oxygen to muscles leads to lactic acid, which in turn leads to fatigue.
However, as often goes in science, others had differing ideas, but it took some time for those ideas to emerge. Most notable is the work of Dr. George Brooks, currently on faculty at the University of California, Berkeley. Dr. Brooks has spent his life studying lactate metabolism, and it all started with an experiment where he gave rats radioactive lactic acid and found that they burned it for energy faster than anything else he could give them.
According to Dr. Brooks, an athlete in his own right, “It looked as if lactic acid was there for a reason - it was a source of energy.” Dr. Brooks published the findings in the late 1970's. Other researchers challenged him at meetings and in print because it went against everything they thought was right.
Eventually other researchers confirmed the work and gradually the thinking among exercise physiologists began to change.
The Correct View of Lactic Acid
The correct view of lactate metabolism is emerging into common knowledge, and it’s definitely a good thing because the knowledge is very powerful for coaches and athletes alike. While Part Two of this series will talk about the current knowledge of why we get sore, the last piece of this article will describe how best to view lactate…as your friend.
Humans, like most other animals, derive useful energy from carbohydrates by first breaking that carbohydrate down from a six-carbon glucose molecule, to two three-carbon lactate molecules. This process is known as glycolysis, and it does not take oxygen, and the amount of energy produced is very small. These two lactate molecules then form the “link” to a process known as oxidative metabolism, where the two lactate molecules are broken down to carbon dioxide and water. This process generates a lot of useful energy to do work (like lift weights, sprint, or anything else we do). So lactate is more properly seen as the essential link between these two processes, which have classically been seen as distinct.
Why Lactate is Your Friend
During his experiments, Dr. Brooks discovered that the muscle cells take in the lactate and burn it for energy to power the workout. Since these early studies, research on elite athletes such as cyclists, rowers, and others have shown that as someone gets into better shape, they don’t actually produce less lactic acid, they produce MORE! However, the athlete also becomes more efficient at using the lactate as a fuel! That is the key, and in fact elite cyclists for this very reason drink lactate during their races! Dr. Brooks’ experiments infusing radioactively-labeled lactate into rats has been reproduced by others using human subjects and non-radioactively labeled lactate, so we can be sure that this same phenomena occurs in humans as well, without the shade of doubt cast by only animal-tested experiments.
Stay tuned for Part Two, where we will examine muscle soreness and what is possibly causing it.
Matthew Johnson – Is a nutritionist and exercise physiologist with a degree in nutritional sciences and toxicology and a certificate in dietetics. He is currently finishing his Doctorate at UC Berkeley in exercise physiology. Matthew consults with companies and athletes from local to international caliber. Matt can be reached at matthewjohnson@mklaboratory.com