Fast-twitch muscle fibers produce lactate during hard effort, while slow-twitch fibers can recycle it as fuel. Building aerobic capacity through slow, high-volume training raises your lactate threshold, letting you run faster before fatigue sets in. Train slow first to unlock speed later.
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And it's hard to convince military people who are type A that to get fast on your mile and a half, you've got to run slow because that's why they're in the military, right? They're like, I'm going to go harder than this dude. We started teaching this for the military mile and a half run. So the people, they were convinced because it was the high intensity culture. Well, I got to run a mile and a half. I need to run it fast. So I have to train fast. But no, the opposite was true that, you know, cuz that really is at what we would call that, that lactate threshold where we're not able to buffer the lactate where ultimately you're starting to get acidic and you shut down. Mm-hmm. It's not because you're out of fuel, it's only a mile and a half. You get enough acidity where you're just like, I'm done. But so to raise that, that level, you have to raise that first level, you know, so that you push it up.
Let's talk about lactate shuttle for a little bit because this is kind of an extension of some of the things you've mentioned over here, but can you break that down in simple terms?
Yeah, in simple terms. So when I was, you know, early track days, you know, and in early medical school, right? So like when you ran hard, you developed lactic acid, right? Like probably everyone who's 56, you know, coach, you know, you're building up lactic acid and then, you know, and then no kidding in medicine, you know, we measure lactate in our septic patients, sick ICU patients. Because it's a marker of hypoxia and it's a marker of mitochondrial dysfunction. So when, when lactate is up, the, the, the system is more acidic. So the basics, you know, written on the back of a napkin for exercise physiology. So we've got 3 fuel sources that our bodies can use for energy, and it's all happening in the mitochondria. So we have billions and billions of mitochondria in our body. Our hearts probably the most, and brain are the most rich in mitochondria. And these need to produce energy. And so we can put fat into these mitochondria. That's a more sluggish process, multiple enzymes involved, a little more oxygen involved to do that. That's why you gotta be going a little slower, more patient to tap into the fat. You know, so it's kind of like a series of gears. Glucose is like, you gotta climb up the hill, hit the gears, You're using glucose right away. Now glucose has a couple different pathways. Right away, glucose shuttles to this other, uh, byproduct called pyruvate and makes lactate. This is the anaerobic system without oxygen, and this is not happening in the mitochondria. This process is happening in what's called the cytosol of the cell. If you were to pull up a model of a cell, you've got the energy factories, the mitochondria. This is where the magic happens.. But if we need energy really quick, and you can do it without using the mitochondria, so you can produce a couple ATP, you know, whereas fat can produce about 120 or 150 ATP. So the— but you get— you can get the ATP right away in the glucose path, but you produce what's called lactate. And that lactate is necessary when you break down glucose, and that lactate produces acidity. It just travels with acidity. The more lactate, the more acidic the environment is, and ultimately that acidity is what makes your brain and your muscles say, no bueno, I'm done. Now, that glucose in the presence of oxygen, that pyruvate can get into the mitochondria, and it's called aerobic activity. But you're using glucose, but you're not really producing the lactate. Not as efficient as the fat, but when you kind of ramp up the speed a little bit too high to allow oxygen to do its job, you're producing this lactate.. Now that lactate can have a couple fates. So the unfit metabolically sick patient, that lactate cannot get back into the mitochondria. There's no— the mitochondria are dysfunctional. We produce acidity. And my patients who have diabetes type 2, they produce lactate getting off the couch. We put them— I do exercise testing here 3 days a week at my hospital. At like stage 1 of a stress test, they're already already gassed, they're already getting acidic. Now, the fit athlete— so these, this lactate is mostly produced by what are called the type 2. These are more your fast-twitch power fibers. The type 1 fibers, these slower-twitch fibers, they love fat, they don't use glucose quite as much, and they don't produce the lactate quite as much. So when you're kind of getting into that pace, maybe a tempo run where you're Breathe a little harder, right? You are, and you're tapping into those faster twitch fibers producing some lactate. But kind of as Frank Shorter discovered, if you have a really robust type 1 fiber system, slow twitch fiber system, what happens is you got this magic shuttle, like a little shuttle bus, that can take that lactate and bring it back into the mitochondria as another energy source. And all roads lead to what's called acetyl-CoA, for the nerds out there. So this lactate can now become a fuel. So it's like, wow, this thing that we thought was a toxic byproduct is a fuel. So that's why people that are massively aerobically fit can do interval training, right? Because you can go do, you know, 8 quarters on the track, but you recover, right? So you build up the acidity, right? We've all done that. But wait, now, like, in a minute, your heart rate's back down. You're fine. You can hit it again. But if you didn't build that type— and that's, that's happening in the type 1 fiber. So you're building up the acidity in the type 2s, but all of that easy training builds the type 1. So you're building this massive base of type 1 fibers that can buffer. So you kind of have to earn the right to do interval training. So without— that's what shorter lineage runners discovered. If they didn't do all of that, you know, all the cross-country skiers in Norway, right? They do 80 to 90% of their Kilian Jornet. You had him on the show, right? He's a massive fat burner. He eats a lot of carbohydrates, but he's— he can burn fat for fuel because he goes out on 6-hour runs without eating, and he's mostly in zone 1. And when you— when you look at an elite athlete, their zone 1 is like our zone 5. You're so fit, right? Like, so he's, he's technically physiologically like, like not even fat maxing, right? He's just out for a walk, but he's running like an 8-minute mile up a mountain, you know, at an effort that you and I would be, you know, gassed. But yeah, so the bigger the base, you know, the higher the peak, you know. So without the base, you're like Pisa, right? You're the one to be like Pisa, you know, big pyramid and— as Seiler says, training is you're baking the cake and racing is eating the cake. So you're building this base to be able to buffer that acidity. And that holds true in any rowing, cycling. Look at the best Tour de France riders, right? They've got this massive— they're not even producing lactate to any degree that would cause any discomfort until they're like at 300 watts. And if you're a cyclist, you know that like, holy shit, right? Yeah, yeah, yeah, it's like all out. But these guys are having a conversation, but that's— and they're not on low-carb diets, or they've built this metabolic machinery that they can use fat for fuel because the type 1 fibers use fat for fuel whether you're, you know, eating more or less carbohydrates. Is, you know, you can shift it a little bit, but it's more about the training that's doing that necessarily than what your habitual diet is. The habitual diet can move it. But I hope that makes sense in plain— Yeah.
So, so, so once again, to summarize, low heart rate training is very important to build that pace that is even gonna be beneficial at a higher intensity.
Yeah. Yeah. Then you can do the mile race or the 5K. We started teaching this for the military mile and a half run. So the people, they, they were convinced because it was the high intensity culture. Well, I gotta run a mile and a half. I need to run it fast, so I have to train fast. But no, the opposite was true that, you know, because that really is at what we would call that, that lactate threshold where we're not able to buffer the lactate where ultimately you're starting to get acidic and you shut down, right? You're not, it's not because you're out of fuel. It's only a mile and a half. You get enough acidity where you're just like, I'm done. But so to raise that, that level, you have to raise that first level, you know, so that you push it up. MUSIC.
