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Lactic Acid vs. Lactate

Author:Dr. Chad Waterbury

Let’s say you run as fast as you can for a minute. The first 10 seconds or so are pretty easy, but then you can’t run as fast anymore. With each passing moment your muscles burn a little more, and your speed slows. What’s happening?

We’ll start with those first 10 seconds that were relatively easy, when your speed was fastest. The first one or two seconds were fueled by the ATP stored within your muscles. Then the next five seconds were primarily fueled by your phosphagen system, which is stored phosphocreatine (PC) within your muscles. So those first seven seconds came from a combination of ATP and PC, and that’s why it’s sometimes called the ATP-PC system, instead of the phosphagen system. Different name, same thing.

Before we move on, it’s worth noting here that even though the phosphagen system is typically described as lasting 10 seconds, in reality it can last up to 30 seconds, depending on the athlete and his/her previous training.

Enter Anaerobic Glycolysis
You know that you can’t run at your top speed, or perform a maximum isometric hold, for more than 10 seconds before things start heading south. That’s because your body’s quickest, “cleanest” energy source, the phosphagen system, has been taken over by your next quickest source for energy: glucose.

How does the body get energy from glucose? Let’s briefly cover a little biochemistry.

The foundation of the glucose molecule is a six-carbon structure. Those six carbons are split into two, three-carbon molecules, which are pyruvate. So anaerobic glycolysis consists of splitting one glucose molecule into two pyruvate molecules.

This splitting forms two adenosine triphosphate (i.e., 2 ATPs), which the body uses to make energy. Importantly, splitting glucose into pyruvate is fueled by NAD+. You might not be familiar with NAD+ but it’s essential for life and present in every cell of your body. After fueling the split, NAD+ turns into NADH. Importantly, glycolysis also releases an acidic proton (H+). The importance of this will make sense shortly, so hang with me.

Anaerobic glycolysis takes place in the sarcoplasm, the muscle’s gel-like substance that includes all of its components, except for the mitochondria.

About the Author

Dr. Chad Waterbury graduated from the the nation’s #1 ranked Doctor of Physical Therapy (DPT) program at the University of Southern California (USC). He’s also a neurophysiologist and author whose unique training methods are used by a wide range of athletes, bodybuilders, figure models, and fitness enthusiasts of all ages and from all walks of life.