You may not have heard of Lactate, but you are most certainly familiar with the burning sensation associated with it. That feeling of needing to stop or slow down during hard efforts out on the bike, at the end of a race, or even chasing your kid.
If you have heard of it, it's probably been in a negative context; viewed as a limiter in endurance events, a problem, a waste product, something to minimize. I'm ashamed to admit that as a young "tough" cross country runner, I stayed away from apples because I thought they contained "lactic acid".
Well, let's clear up some of those misunderstandings.
First, there is no such thing as Lactic Acid, at least not in your muscles. That burning sensation is likely caused by accumulation of Hydrogen ions, which lower pH and raise acidity. We won't get too science-y here, but those Hydrogen ions combine with Pyruvate, a carbohydrate, to produce Lactate. Pyruvate and Lactate readily join and break apart from those Hydrogen ions. So, Lactate is actually a good thing, reducing free Hydrogen ions and producing fuel for our muscles.
So where does Pyruvate come from? During your everyday activities, whether it is sitting on the couch or sprinting to the finish, you are producing energy from both the Anaerobic & Aerobic Systems. The Anaerobic system, generally thought of as short burst energy, breaks down Glucose very quickly to produce Pyruvate, Hydrogen ions and energy for muscle contraction. While Lactate is then produced, there is still excess Hydrogen ions which is probably where Lactate gets its bad rap.
The beauty of Lactate comes in when we bring in the Aerobic Energy System, the system we think of for endurance activity. The most efficient fuel for the Aerobic System is carbohydrates. That's right, the Anaerobic System produces fuel, Pyruvate, for the Aerobic System!! And because of the ready exchange from Pyruvate to Lactate & back again, we can say that Lactate is a byproduct of the Anaerobic System and fuel for the Aerobic System.
Lactate's relationship to both energy systems provides us with the most complete picture we have in determining how much each energy system is contributing to overall energy production. As an example, if there is a lot of Lactate, then either the Anaerobic System is producing too much and/or the Aerobic System is not developed enough to process the Lactate. Subsequently Hydrogen ions builds up and you slow down.