Physiology of Fat Burning Zone and Anaerobic Threshold

Eliska: And last week, we talked about distance and the different types of distance training you can do and today we will take you a little bit into the physiology of distance and interval workouts because this is the time of year when we start really hitting those intervals and getting the heart rate high.

A lot of people hear distance and they’re like, “Oh, yeah, that’s the fat burning zone. I have to do a lot of slow activities to lose my weight – if I need to lose my weight.” Well, the scientific approach behind it is a little bit different. So Karmen, let’s talk about that.

Karmen: It is true that you’re going to burn fat when you’re in a low heart rate, like your distance workouts and your over distance when you’re in level one and level two. However, well, you’re going to burn more percent of fat relative to carbohydrates. But when you go into higher training zones like level three and above, you are going to burn more fat overall.

Eliska: So the percentage of burning the fat and the higher heart rate levels is smaller but overall it’s still bigger than …

Karmen: It’s still bigger than it would be when you’re in level one.

Eliska: That’s really important to know for all of us really who are trying to stay fit and fit in our jeans.

Karmen: Yes.

Eliska: That’s a good advice. Well, intervals. What are really the intervals? What are we doing when we’re getting into level three, level four, five? Basically we’re starting to burn different types of energy…

Karmen: Yes, energy.

Eliska: Energy blocks. Just like you’ve said, fat and carbohydrates.

Karmen: Right.

Eliska: So when we’re getting into the level three, that’s when we’re hitting the anaerobic threshold which basically means that you start burning your carbohydrates without using oxygen because you are working so hard that the oxygen is not coming into your body enough to –

Karmen: Quickly enough.

Eliska: Yes, quickly enough to actually create pyruvate that happens that is being created when you’re burning carbohydrates with your oxygen. So instead you create lactate. People are like, “Ah! Lactate! It’s the biggest enemy.”

Karmen: Yes.

Eliska: But …

Karmen: It’s not true.

Eliska: But it’s not true, exactly. So lactate and pyruvate are kind of like brothers, right? Pyruvate is the, oh, good brother that gives us a lot of energy. We get around 36, I believe, ATP which is the actual energy that moves our muscles from burning pyruvate and we get definitely less than 10 ATPs from burning lactate. But we’re still getting the energy.

Karmen: Yes.

Eliska: So, when we do intervals, that’s when we start getting that lactate. We start burning it and that’s why we do the intervals. When we do intervals, we want to feel the pain of getting the lactate in the muscles because that’s where we’re going to race.

Karmen: That’s where we will be racing. So we want to get used to that in our training, so there are no surprises when we get to our race.

Eliska: Exactly. Because when the lactate is created, it really hurts.

Karmen: Yes.

Eliska: So when you’re racing and you’re not used to it, when you never did interval like that, you’re going to be like, “Oh god, my legs are so sore. My arms are kind of totally stiff, like pieces of rocks.”

Karmen: Right.

Eliska: So that’s why the intervals are really important.

Karmen: And we become more efficient. The more we train where we’re using lactate and pyruvate, the more efficient we get at it. So come race time, our body is primed and knows exactly what to do.

Eliska: And we can push the lactate threshold higher and higher in our heart rate. So we hit it later on in our competition.

Karmen: Yes.

Eliska: One interesting thing that people don’t really know about lactate, the lactate keeps burning after you stop exercising. So let’s say you finish your race and you’re like, “Oh god. I need to catch a breath.” You’re catching a breath right behind the finish line. You’re still burning your lactate. The lactate burns out and then you start burning the pyruvate. So the common misconception is, oh, I have to do my cool down so I get the lactate out. You actually don’t have to.

Karmen: Lactate clearing.

Female Speaker: You don’t have to do your lactate clearing.

Karmen: Yes.

Eliska: We still like to do cool down because it mentally relaxes you.

Karmen: It gives us good closure.

Eliska: Exactly, good closure and it’s another great way how to get more hours in your training.

Karmen: Yes, your overall volume.

Eliska: So hopefully you enjoyed some of our tips today. Let us know if you have any questions and next time we will talk more about intervals and different types of them.