Author: Liz Jones

For many years lactic acid seemed to be the ultimate enemy of a workout. It was thought to accumulate in your muscles, break them down, prevent you from completing your sets, and even make you sore when simply walking up stairs the next day. Turns out it has all been a misconception.

You have two ways of producing energy for your muscles; one is without oxygen, called glycolytic or anaerobic. The other is with oxygen, called oxidative or aerobic. Most often the anaerobic pathway kicks in first. It’s those first few contractions where your muscles are trying to do a significant amount of work, with the amount of oxygen suitable for a dormant muscle. Once your heart rate picks up, and you’re breathing harder, the oxygen travels to the in use muscles faster, and in higher quantities via your blood. You are then able to produce energy via oxidative metabolism.

Here’s the kicker. Even when you have been exercising for a while, and your oxidative metabolism is in full effect, you are still using the anaerobic pathway. Your fast twitch muscles use the anaerobic pathway to produce ATP, the energy source for all cells.

A byproduct of anaerobic metabolism is lactic acid. Lactic “acid” is not actually an acid, but is lactate and hydrogen ions. The accumulation of hydrogen ions in the muscle cells is what prevents the muscles from contracting. Lactate is the buffer for the hydrogen, and is also an energy source for the cell itself. The term lactic acid comes from the change in pH of the muscle cell due to the increase in hydrogen ions, making the cell more acidic. The consequence is the burning sensation you feel when you are working your muscles to their maximum capacity.

Lactate is important for high performance exercise. It is used as a very quick way to produce ATP compared to oxidative metabolism. High performance athletes have lower blood lactate levels because they have trained their muscles to recycle the lactate into anaerobic metabolism more efficiently. This means less lactate is being shuttled to other organs for processing, and more is staying in the muscle cells. More energy, at a faster rate, is ideal for the function of fast twitch muscle cells during intense bouts of exercise. Iñigo San Millán wrote a great piece on the subject if you are looking for a more detailed explanation.

 Your body uses lactate not only to create energy for your muscles, but also to stimulate regeneration of myelin in your brain.  Johanne Egge Rinholm conducted a study on rat brains, and determined that myelin with high concentration of lactate grows faster than myelin with lower concentrations. This is an important discovery for recovery from injury, and preventing damage from disease.

So, next time you are sore, and you start to blame lactic acid, think twice. Your next day soreness, often referred to as delayed onset muscle soreness (DOMS), is likely due to factors other than lactic acid. More on DOMS to come soon!

SOURCES

Hjelle, Ingeborg A. “Lactic Acid Protects the Brain.” Institute of Basic Medical Sciences. University of Oslo, 2 Jan. 2012.

Kravitz, Len, and Lance C. Dalleck. “Optimize Endurance Training.” Research Interests. University of New Mexico, 2005.

San Millán, Iñigo. “What Is Lactate and Lactate Threshold.” TrainingPeaks. N.p., 17 July 2014.

Sanders, Robert. “04.19.2006 – Muscles Burn Lactic Acid as Well as Carbos.” UC Berkeley News. UC Berkeley, 19 Apr. 2006.

Westerblad, H., J. D. Bruton, and J. Lännergren. “The Effect of Intracellular PH on Contractile Function of Intact, Single Fibres of Mouse Muscle

Declines with Increasing Temperature.” The Journal of Physiology500.1 (1997): 193-204. NCBI.

Photo: “Skeletal muscle – cross section, nerve bundle”. Licensed under CC BY-SA 3.0 via Wikimedia Commons – http://commons.wikimedia.org/wiki/File:Skeletal_muscle_-_cross_section,_nerve_bundle.jpg#/media/File:Skeletal_muscle_-_cross_section,_nerve_bundle.jpg