Back in the early twentieth century, a scientist by the name of Otto Meyerhof made a breakthrough discovery that changed the face of sports training for years to follow. Meyerhof did a test where he cut a frog in half, and placed its rear section in a sealed jar, away from oxygen. He then sent an electric shock through the legs and watched them twitch for a few seconds before slowly coming to a stop. Afterwords, Meyerhof found the legs to be saturated with lactic acid. From that day on, the theory remained that a lack of oxygen to the muscles leads to lactic acid build-up, and finally to fatigue.

This theory has driven the training sessions of nearly every serious athlete for the last 80 years. We are taught that if we worked our muscles past the lactic threshold, our muscles would fatigue, eventually forcing them to stop working.

I have read books such as Joe Friel’s “The Cyclist’s Training Bible: A Complete Training Guide for the Competitive Road Cyclist.” The book teaches you how to maximize your workout while staying above that lactic acid threshold. He uses the analogy of a funnel, saying something like, your muscles are similar to a funnel, if you slowly pour water into the funnel it will drain out without a problem, but if you fill faster than it can drain, the funnel will fill up and slowly overflow. This is how your muscles work, if you feed them too much lactic acid, they will retain more lactic acid than they burn, causing fatigue.

Everything about what we have been taught about lactic acid is wrong. According to George A. Brooks, a professor in the department of integrative biology at the University of California, Berkeley, Lactic acid is actually a fuel, not a caustic waste product. Muscles make it deliberately, producing it from glucose, and they burn it to obtain energy. The reason trained athletes can perform so hard and so long is because their intense training causes their muscles to adapt so they more readily and efficiently absorb lactic acid.

So, the question remains, If lactic acid isn’t causing fatigue, what is?  When muscle cells convert glucose or glycogen to lactic acid, mitochondria takes the lactic acid and uses it as fuel. Just think of mitochondria as the energy factories of the muscle.  The more mitochondria that you have in your muscles, the more lactic acid you can convert to energy.

When it comes down to it, coaches and experts like Joe Friel knew more than the scientists did. It turns out that they weren’t teaching us how to increase our lactic thresholds; they were showing us how to increase our mitochondria. When you train hard before a race, you are telling your body to start building mitochondria.

The next time someone tells you they can feel the lactic acid building up in their legs, just tell them they need more energy factories in their muscle.

Get more info on the lactic acid myth here [nytimes.com]