Lactate Is Your Friend
Lactate, or lactic acid as it is commonly known, gets a bad rap thanks to some faulty science from the 1970′s. While an excess accumulation of lactate contributes to why runners slow down at the end of races, lactic acid itself isn’t responsible for the muscle fatigue that causes you to do the skeleton dance at the end of a race. In fact, lactate is actually a source of energy.
Hydrogen ions are the real culprit.
The cause of your muscle fatigue is actually the result of a buildup of hydrogen ions. For each lactate molecule produced by the body, one hydrogen ion is also formed. Hydrogen ions lower the blood pH and make the muscles acidic. This acidity irritates muscle nerve endings and causes that pain, heaviness, and burning mistakenly attributed to lactic acid.
How lactate really works:
As you probably already know, your body breaks down glucose for energy, and a byproduct of this process is lactate. During easy running, your body reconverts and recycles this lactic acid back into energy (through the Cori Cycle) and carries away hydrogen ions with it. Therefore, the production of lactate, and the clearance of hydrogen, will remain relatively constant while running at an easy aerobic pace, which doesn’t require a huge demand for energy.
As you continue to run faster and demand more energy, the production of lactic acid will slowly increase. At some point, whether it be too fast a pace or holding a steady pace for too long, the production of lactic acid will soar and your body will no longer be able to convert lactate back into energy. At this point, lactate can’t grab its hydrogen ion to reduce the concentration of hydrogen in the muscle cell. And, as we learned previously, hydrogen is what causes the muscles to seize up.
How this knowledge changes your approach to lactate threshold training:
Now that we understand how lactate really works in the body, and have discovered the true culprit of our muscle fatigue, how does that change our approach to training? Recent research indicates that the goal of endurance training shouldn’t be to reduce the production of lactic acid but to improve the ability to clear lactate from the blood. Simply speaking, we shift from the idea of increasing our tolerance for lactate production to the idea of increasing how efficiently our body utilizes lactate as an energy source.
The faster we can train our body to reconvert lactate back into energy in the liver, the longer and faster we can run at a given pace. Therefore, the goal of your lactate threshold training shouldn’t be how to reduce lactic acid production, but instead to train your body to use it efficiently. While this shift in thinking is slight, it radically changes how you approach your lactate threshold workouts.