"Lactate is not a dead-end metabolite"

Those were the words my undergraduate exercise physiology professor loved to share during our discussions of anaerobic metabolism. He rarely used the term "lactic acid," but referred instead to "lactate." You should too. Your muscles don't produce "lactic acid" but rather a compound called "lactate" in response to intense exercise. This is in response to intense exercise, exercise that makes the energetic need in the working muscle higher than what’s produced by aerobic metabolism alone. But the cool thing about lactate is that your body can use it as a source of fuel. Another professor of mine used to remind us that "the heart loves lactate" as an energy source (just as the muscles love using stored glycogen). And what you're probably thinking is Wait, I thought the muscle soreness I feel after a hard workout is from the lactic acid. Nope. The soreness is primarily due to a mechanical breakage at the cellular level of the muscle. You end a track workout with a certain percentage of your muscle cells literally broken—and you need some recovery time to allow them to repair…which they will.

So why all this exercise physiology? Simple. I want you to embrace lactate and workouts that introduce lactate as part of what helps you become better runner. I love to assign athletes fartlek workouts where the "on" portion is run faster than the threshold portion. Running faster than threshold pace will bump up the amount of lactate in the system. This is followed by running the "off" portion more slowly than threshold pace (but still at a steady pace), which allows the body to deal with the lactate and make a physiological adaptation. The bottom line is that you can teach your body to become better at dealing with lactate, and this efficiency helps runners, from 800m runners to marathon runners

Jay