Lactic Acid and Running – It’s Really Not Debatable Anymore

By Rick Morris

I consider myself to be a patient person. I also feel that I am tough enough to take a lot of criticism. I’m not breaking my arm trying to pat myself on the back. As a coach and a writer those are two traits that are necessary for success. Every time a writer publishes a controversial work or a coach voices an unpopular opinion on training they are painting a sign on their back that says “go ahead and blast me”.

There are a lot of subjects in the world of running that are controversial enough to support a debate or criticism. Strength training for runners, classic periodization versus multi pace training, high volume versus high quality and dynamic versus static stretching are just some examples of running themes that have both pros and cons. When writing or speaking about subjects like those I expect and welcome both disagreements and debates. I always enjoy a good, lively session of give and take. It can be both enjoyable and educational to both sides of the debate. But there is one subject that I feel is incontrovertible. Interestingly enough, it’s also the area where I get the most disagreeing emails, some of which border on hate mail. That subject is lactic acid.

The myth that lactic acid is a waste product that causes muscle fatigue just continues to hang on despite the volumes of recent scientific literature that proves just the opposite. All current research shows that lactic acid is not only a valuable source of energy but may actually help prevent muscle fatigue.

The long held association between lactic acid and running began way back in the 19th century when chemists found that juice fermented without adequate oxygen developed acid products. About 50 years later, the scientists of the time found that muscles worked to exhaustion also accumulated lactic acid. Those early researchers then prematurely assumed that the lactic acid was the cause of the muscle fatigue. That remained the accepted theory for many years and still hangs on today. But those early scholars made the mistake of putting the cart before the horse. They just assumed that the lactic acid was causing the fatigue. They didn’t consider that perhaps the lactic acid was the bodies response to muscle fatigue rather that the other way around.

Our bodies are incredibly efficient. There is no process in place that isn’t needed. Even pain has a purpose. It’s a signal to us that something is going on that your body doesn’t like. There is also a purpose to lactic acid. It isn’t just a waste product that throws a wrench into our body works.

As our knowledge of the role of lactic acid grew it became evident that those early beliefs may be wrong. In the mid 1980’s, researchers discovered the “lactate shuttle”, which showed that lactic acid moves freely in and out of muscle cells to provide quick energy and also to produce glycogen. The lactate shuttle works like this – the lactate that leaves a muscle cell may be picked up by a nearby muscle cell or travel through the blood stream to other muscles cells or tissues. The cells picking up the lactate can either convert the lactate back to pyruvic acid, which then enters the Krebs cycle to produce energy or can be converted into glucose or glycogen which enters glycolysis to produce energy.

That news that lactate provides large amounts of energy should have been enough to convince runners that lactic acid is a good thing, but the myth stuck around. Runners, coaches and even expert running commentators still called lactic acid a waste product. Nearly every distance running event on television had a commentator talking about lactic acid causing “oxygen debt.” Now we have even more research that proves the value of lactic acid. Two recent studies, one in Denmark and the other in Australia have proven that lactic acid actually fights fatigue and makes your muscles contract more efficiently.

Your muscles only contract when your central nervous system (CNS) tells them to. Your CNS does this by sending an electrical signal to your muscle cells. Your muscles contract when the electrical charge causes potassium inside your muscle cells exchange places with sodium outside your muscle cells. During intense exercise, potassium ions have a hard time finding their way back inside the cells and they start to build up outside your muscle cells. This build up reduces both the electrical charge and the ability of your muscles to contract. In other words you begin to suffer from muscle fatigue.

This is where lactic acid comes to the rescue. Both studies showed that accumulating lactic acid is used to diminish the effects of the accumulating potassium ions, help them back inside your muscle cells and restore the function of the CNS signaling system.

New research is on the fatigue reducing role of lactic acid is flowing in like a raging river. As new discoveries are made the role of lactic acid will continue to grow and change. What is clear is that our bodies are smarter than we are. Every function plays an important role whether we know it or not. What is also clear is that the idea that lactic acid is a waste product is dead and gone. Isn’t it time to put it to bed?