A guide to cardiorespiratory training at any fitness level to improve longevity (AMA 79 sneak peek)

— Peter, welcome to another AMA. How you doing? I'm doing very well. Thank you for having me back. Always welcome to have you. I see every time we do these you bring something more and more to each recording. — What have what have I brought this time? I don't know. I'm not even aware. Nothing you can think of? Nothing jumps out? No new additions to the body? No, but given that we've now introduced carve outs at the end of these I've it's made me that much more aware of um how much I am the perfect target of YouTube and Instagram ads because I could I could create an entire podcast called the carve out where I just talk about you know the things that I buy when they're uh served up to me as ads that I end up liking. Have you bought one thing today? Uh not today, but I did get something really awesome 2 days ago. Uh it arrived 2 days ago. Anything you'd like to share with the group? Heck no, I'm saving it for a carve out uh maybe next month. I want to I put these things to the test. Let me tell you, I am a I am I'm a serious tester of product. So, the thing that I got so far, I've already tested it once. It was insanely good. So, I just need to I need a few more reps with it and if I'm still digging it in a month, it might make it to the carve out list. That's great. Uh it's exciting because I don't think people realize what you're talking about could be a legitimate thing that is actually beneficial to health and longevity. And it could be the dumbest $20 gadget that has ever existed. And we have no way of knowing which one it is when it comes to that spectrum. — Well, I'll give you a hint. It was served up on a YouTube ad, so it's definitely not the former but I will say it's also not the latter. — Leaving people hanging. There there's a lot of daylight between those two, so. Yes, you just tend to live on the spectrums though, right? Like you kind of go one or the other. Uh you know, that's like the only thing you do in moderation is moderation, which turns out is the same with engaging in YouTube and Instagram ads. You like to go all in. — [sighs] — So, with that said what we're covering today one topic, cardiorespiratory fitness in simpler terms for people zone two VO2 max. So, this is a topic we have talked about over the years on different podcasts, different guests, different articles but it's also a topic that we get asked about by far the most partly because of the interest in it and also I think because of how open you are on how it is the biggest and strongest modifiable predictor of both health span and life span. Meaning it's the biggest impact that someone can do something about it. So, that's why we decided to kind of dedicate this AMA gather all the questions and try to make it a one-stop shop for everything relating to how to measure, track, improve zone two VO2 max through training. We'll cover how this relates to people who have a lot of time to work out, people who have a little time to work out. We'll look at how it relates to people who are just starting training, people who have been training for a long time, older adults, if anything changes for women in particular, and more. We'll also look at if your opinion has evolved around some recent debates and discussions around zone two, lactate, how to balance volume and intensity with the goal of not having your best exercise month ever and then stopping, but more so long term. So, with all that said anything else you want to add before we get started? Yes, um this was an idea that when the team pitched it to me um my initial response was I don't think this is worth it. We've already generated plenty of content on this. It's probably one of the things I talk about more It's It certainly would be within the top five things that I talk about. Um and the team I think was able to get me uh convinced and I believe rightly so by saying, "Yeah, Peter, that's kind of the point is if someone were to try to go out there and aggregate everything you've said on this topic, it would be a full-time job and it would and I think someone even shared with me how many hours and hours of content it would be and it was, you know, triple digit hours. Um and they said that's great for the person with an encyclopedic memory who is a lifelong you know, devotee who doesn't have a job. Um but most people aren't going to fit into that category and it would be really helpful to have a practical guide, not just a theoretical guide to this. Um and so that kind of won me over. Um and so I guess I would just say kind of kudos to the team for convincing me that this was the way to do it and I'm really kind of happy with the um the way they've kind of crafted a story around this, so let's dive in. Before we do, quick question. Do you think if the team started to put their arguments in forms of videos that we ran as Instagram or YouTube ads, you'd be more willing to listen? I mean, if you could be good enough, but you have to catch me within the first 10 seconds of the ad or I'm skipping it, right? So, you've like I don't know that that's a skill set that exists on our team. We don't practice that skill of catch you in the first 10 seconds. No, we practice more of we will get you at the end of 2 hours after explaining in rigor. All right, so with that said, I think what would be

helpful to start is looking at real quick why is cardiorespiratory fitness a central pillar in not only your approach to life span, how long you live, but health span. Yeah, so again, if you've been listening to me talk about this for years, you can literally go to your podcast player and hit forward for a couple of minutes. You don't need to hear this. Um but I do want to spend at least a minute on this idea that cardiorespiratory fitness is one of the most important and modifiable. It's very important that we're talking about modifiable predictors of both how long you're going to live and how well you're going to live. Um and so if you look at all the predictors of all-cause mortality, which remember that's the holy grail metric of longevity cardiorespiratory fitness outperforms every other variable we can measure. This includes blood pressure. This includes cholesterol. This includes BMI, smoking. It even includes age, which just blows my mind. Um so cardiorespiratory fitness CRF represents how efficiently your heart and lungs and blood vessels and muscles can work together to deliver and utilize oxygen. Um so the more efficient that system is, the more physiological reserve your body has. And it's this reserve that allows you to tolerate stress. This stress can come in the form of an infection, a surgery, uh or just, you know, frankly the day-to-day demands of living. Now, this has been most typically and most repeatedly measured using a test called VO2 max. You've heard me talk about this, of course, um and it's become a very popular thing that people talk about. It's the maximum rate at which the body can utilize oxygen tested, of course, during maximal efforts, which require exercise. Um so this number is expressed in milliliters of oxygen per kilogram of body weight per minute. Um but it can be estimated using something called METs or metabolic equivalents, where one MET is equal to 3. 5 ml per kilogram per minute of oxygen uptake or utilization. Um so I would say that the reason that VO2 max has become such a popular way to do this is because it is a standardized test. That doesn't mean it's always done correctly and we've got plenty of examples of how this can be done incorrectly, which is why for our patients, we actually do the test. We got sort of tired of relying on other labs to do it. Um but for the most part, a well-trained technician can do this consistently um and that makes it easy to study and that's why in the literature you're going to see so much discussion where it comes down to METs or VO2 max. The two can be used interchangeably. Um and you won't, for example, see that when it comes to zone two. So, we're going to talk a lot about that today, but I just want to point out zone two is a much more difficult area to navigate because it's not a maximal effort. It's an in between effort. Um VO2 max is a maximal effort. So, when you tell somebody to basically floor it until they're going to keel over, um that's actually much easier to achieve. Now, to put some context around the importance of VO2 max in mortality, again because it's been studied, um if you're in the bottom quartile or um quintile, so bottom 20 to 25% of the population with respect to your VO2 max, you've got a four-to-five-fold higher risk of mortality, all-cause mortality in any given year than those in the top 3%, two to 3%. Um so that's a that's a pretty big jump, but keep in mind even tiny little jumps, um you know, say moving from uh the uh second quartile to the third quartile will still have uh easily a 50 to 75% improvement in all-cause mortality. So why is this such a powerful relationship? And I think it comes down to not just what the number represents, which is everything I've talked about vis-a-vis oxygen delivery and utilization, but I think it's and I've said this before, but it but I think it bears repeating. It's that measures like VO2 max, just like strength, they're actually integrators of work done. So if a person has a VO2 max that is low and their aspiration is to have a very high VO2 max, they can, but it will take potentially years and countless hours of work done. And that work will be done at the level of their cardiovascular system, their pulmonary system, their hematologic system, muscular system, metabolic system. And all of those things will have to work and work for hundreds of hours to get a desired outcome. And if you think about that, that's much more frankly impressive from a physiological perspective than taking a pill that lowers your cholesterol. And it's not to say that taking a pill that lowers your cholesterol doesn't improve outcomes, but it's not going to come close to improving outcomes as much as this does on average. There are edge cases. There are some individuals with familial hypercholesterolemia where, you know, that pill that lowers their cholesterol will have an outsized benefit. But by and large, this is why uh things that improve cardiorespiratory fitness or strength tend to have such an impact on mortality.

And then beyond mortality, can you also talk about the healthspan benefits? So what you refer to is not only how long it can help you live, but how well live. Yeah, I think the argument here is just as strong. Of course, we just don't have the same uh the data are not quite as objective because healthspan is not as objective. So what I might aspire to be able to do that would define good healthspan for me might not be the same as you, Nick, and is not going to be the same as every person that is listening to us right now. But what we do know, and I think we'll show at least one figure to that effect today, is that VO2 max declines quite predictably with age at about 10% per decade. Um but you know, oxygen cost of doing things doesn't change. So whether it be climbing stairs or lifting something up or chasing your kids around or playing a sport, those things don't change. So if you have a declining capacity to deliver and utilize oxygen in the presence of constant demand, at some point those curves cross and what that effectively means is you start losing the ability to do these things. And again, we'll talk about this in much more detail when we get there, but as I as I think a figure can represent better than what I'm saying necessarily, our objective is to be able to maintain optionality around being physical for as long as possible. And that is tantamount to having as high a VO2 max as possible in addition to being as strong as possible.

possible. And when talking about cardiorespiratory fitness in the past to kind of help people understand it in a similar way, you've often talked about the base and peak model. Can you just walk through a little bit more about that framework and how different exercise and intensities can contribute to each component of that? Yeah, so I talk about this cardiorespiratory fitness triangle and I can't take credit for this at all. It was one of my cycling coaches that came up with this. So the idea was that you have a picture a triangle with a base and a peak. And the base is what we think of as your capacity to do sustained submaximal effort over a long period of time. So think of something you could do for hours. And then the peak is represents your maximum aerobic output. So what you could sustain for, you know, 5 to 10 minutes. Obviously, there are, you know, so many gradations here, right? Your functional threshold power, which is what you could obtain for an hour, is obviously much narrower is, you know, is a smaller number than the than the peak and a shorter number than the base. So anyway, the goal here, if if you're trying to maximize your total aerobic capacity, is to maximize the area of this, you know, cardiorespiratory triangle. And of course, to do that, you want to have the widest base and the highest peak possible. Um and these require different forms of training. So if you just trained at one intensity level the whole time, you would increase both of these things. I want to be clear on that point because it creates so much confusion. If you only parked yourself at one level of training, you would, through enough volume, increase both of these. But that's not the way to maximize the problem and it's certainly not the most time-efficient way to do it, nor is it necessarily the best way to do it. In fact, it's almost assuredly not given the fact that no high-level athlete trains that way. So the base is ideally built through adaptations that help you utilize oxygen more efficiently to convert fuel, but mostly fat into ATP. So what this is really geared towards is improving mitochondrial density and efficiency and optimizing fat oxidation and lactate utilization. Conversely, the peak, which again is that VO2 max, represents the ceiling for oxygen delivery primarily, but utilization. Um and it's driven by how well this system can deliver oxygen to the mitochondria. That's primarily the bottleneck. It's how much oxygen can you deliver to mitochondria, right, versus the base, which is how much can you utilize substrate efficiently. So when it comes to delivering oxygen [clears throat] to the mitochondria, there are really four big drivers, right? So there's the diffusion of oxygen from the lungs into the blood. There's cardiac output, so that's heart rate and stroke volume. Then there's the oxygen carrying capacity of the blood, namely hemoglobin. And then there's the muscles' ability to extract this. But as I said a moment ago, it's the cardiac output that is the main driver here and it is the one we're most sensitive to in reduction. So again, what drives cardiac output? Primarily is stroke volume, how much blood comes out of the heart with each pump, and heart rate. And of course, when you're at a VO2 max effort, you're getting to maximum heart rate. So somewhere between 70 and 85% of the variability in VO2 max is accounted for just by this one variable. In the show notes, we'll include a whole bunch more detail on this if anybody kind of wants to nerd out on this stuff. I love this stuff, but I don't want to spend any more time on it right here. So as I kind of alluded to, it's very tempting to and I want to take I want to apologize if I've ever created the impression or oversimplified this and it's possible that I have. Um that you know, zone two is what you do exclusively to build your base and high-intensity workouts is the only thing you do to build your peak. As I said, these systems work together and if all you did was zone two, you would absolutely get a wider base. You would also raise your peak. Similarly, if you did, you know, higher intensity training, you would increase your peak, but you would also widen your base a little bit. The key, as we'll get into in the nuance, is what is the optimized way to utilize time around different volume and intensity requirements. So um how much total work can you do? How much cardiorespiratory fitness training can you do? Um that's probably the single biggest determinant. But that involves a min-max problem, which is a big part of what we're going to talk about today. So that's how I think about the triangle. And when

talking about zone two, you've often talked about fat oxidation, mitochondria, lactate. Often times, I think these terms can be a little confusing for people, and so I think it's always helpful to kind of like re-look at them and explain it. So do you mind just spending a few minutes walking through like the cellular mechanisms that are involved in cardiorespiratory fitness just so everyone is kind of familiar with the terms you may or may not use throughout here. Yeah, so it's really funny because I've noticed some amazing memes on Instagram where you basically have people that are making fun of anybody that uses the word mitochondria. So somehow and I because I don't really pay attention to the the wellness influencer health space, apparently the word mitochondria is now just one of those buzzwords that you should throw around as much as possible. And so, you know, if you're playing sort of wellness influencer bingo, you're going to get a lot of points for mitochondria. Um, I can't remember some of the other awesome words that are just basically pathognomonic for buffoonery. Uh, can you I'm sure you've Have you seen any of these memes? They're amazing. It's like mitochondria, inflammation, uh, gut biome. Like they've got all the buzzwords, right? So, um, Protein? Protein. I'm sure, right? So, so you've set me up now to to trigger a bingo card. Um, but I guess you're right. There you can't have this discussion without doing this. So, so hopefully I'm going to get an exemption for my use of the word mitochondria here. So, um, at the foundation of your cardiorespiratory system, um, are these organelles called mitochondria. And of course, all of you who took a high school class in biology will remember that they're referred to as sort of the little power units of the cell. And the majority of our ATP is produced by them. And again, ATP is the currency for energy. Um, and I just because I can't resist giving one more lay level of detail, the way ATP work is they donate ATP phosphates. They donate one of those phosphates, and it's that liberation of energy that comes from that chemical bond uh, that creates energy. So, you know, the mitochondria can generate ATP from either fatty acids or pyruvate. Pyruvate is is the breakdown is a intermediary breakdown product of uh, glucose uh, via a process called glycolysis. And both of these processes are constantly occurring. Um, it's just the question is what's the balance in which they're occurring? And of course, are these both equal? No, they're not, right? Each process has a tradeoff. So, the tradeoff would simply be stated this way. If you are optimizing for efficiency, and you don't care as much about the speed with which you can deliver ATP, you want to take that more aerobic pathway. Meaning, utilizing oxygen and shuttling the breakdown product of fatty acid or glucose, um, either in the form of pyruvate or acetyl-CoA into the mitochondria, uh, to use an oxidative pathway to generate lots of ATP per units of carbon that go in. The problem with that is, as the demand for ATP accelerates, you have to make a tradeoff. sacrifice. The body says, "I'm sorry, I can't do this anymore. I have to go down this quicker path using glycolysis, where I turn glucose into pyruvate, ultimately into lactate. I don't get nearly as many ATP for it, but I can do this I can deliver much more ATP to the muscle. " Now, I can't do this indefinitely. There's a whole problem associated that which we'll talk about, but that's effectively at the high level the tradeoff. So, another way to think about this is through the lens of the fibers that are involved. And again, these are terms we've used on the podcast before, but this the goal of this podcast is kind of tie this all together. So, at lower intensities, you have these type one or slow-twitch muscle fibers. And again, I think the term slow-twitch, it's um, uh, it it it does to some extent reflect the speed with which they twitch, but I think a more important way to think about them is they're slow to fatigue, um, and they're more endurance-based fibers. So, again, at lower intensities, they're the ones that are doing all the work, very rich in mitochondria, deep red. Uh, they excel at oxidizing fat, um, and they're very, very efficient. As the intensity increases, we have to start recruiting more of the type two fibers. These are fast-twitch fibers, which again are more contractile in their force, but they're also fast to fatigue. They have less mitochondria, and they're going to recruit uh, and rely more heavily on glycolysis, um, that's happening outside the mitochondria. So, um, initially, lactate, which again kind of gets a bit of a bad rap, but again, we've done an entire podcast on this, and we'll link to the podcasts on this topic. But the most important of these is definitely the one with George Brooks. Um, initially, the lactate gets recycled locally. Um, so it's shuttled, um, to neighboring type one fiber. So, a type It gets generated in the type two fiber, it gets shuttled to a type one fiber, it gets converted back into pyruvate, and then the pyruvate goes into the mitochondria to produce more ATP. Um, that's called the lactate shuttle. Um, but again, these things are constrained by demand, and therefore, as output increases and demand increases, lactate production in the type two fibers begins to exceed the capacity uh, for what can be done locally, right? In the mitochondria adjacent. And at that point, lactate spills into the bloodstream. So, if you were measuring lactate in the bloodstream with a continuous lactate monitor, which by the way, these things are uh, easily in prototype, and there's some that are probably in the market. This would be something you can appreciate in the future. You might start out an exercise session where your lactate is, you know, resting at 0. 5 millimole, um, everything I just described up until this point would not increase that, even though locally lactate levels are rising. Um, but once it starts spilling into the bloodstream, now you actually have to rely on other tissues in the body. The heart, other muscles that are not being, you know, utilized at this point in time, they have to start clearing it using lactate as fuel, as we've even learned from George Brooks. The brain will do this as well. The liver also can convert that lactate back into glucose via gluconeogenesis. Um, and this basically allows the body to maintain certain levels of lactate, um, at a new baseline that is above the original baseline. Um, this is usually referred to as the first lactate threshold. And again, for a metabolically healthy individual, um, and someone who's metabolically flexible, meaning they can go back and forth between utilizing glucose and fatty acids, this falls at about two millimole of lactate. Um, that is what we refer to as zone two. Now, again, if some of those conditions aren't met, if you're not a metabolically flexible person, using that uh, first threshold of lactate, um, at two millimole is not going to happen. There are people who walk around at rest with a lactate level above two. Okay, but the point here is you can maintain you're now at a new steady state, where if you remember, the first steady state is where the local tissues are able to uh, offset lactate production at the rate that um, uh, it's being produced, right? Consumption and production are equal locally. Then you have this sort of second level, which we refer to as the first lactate threshold, cuz it's the first one we're measuring in the plasma, and that's where now the systemic tissues are able to balance it. But now we get to a third level, um, uh, of lactate, which is really called the second lactate threshold, and that's at higher and higher levels. And at this point, once the body gets above that level, um, and this level varies quite a bit by individual. Um, I'm not going to Maybe if we have time, I'll go into how you can measure that. I talked about this at length in the first podcast with um, uh, with um, uh, Olaf Alexander Boo. Um, but we can come back to that. But anyway, at these higher levels of output, glycolytic lactate production in the working muscles completely sup- um, surpasses the body's ability to clear it. At this point, blood lactate starts to rise much more sharply. Um, it accompanies um, it's accompanied by hydrogen ion, right? Because the lactate, um, is negatively charged, the hydrogen is positively charged, so they're balanced kind of one to one. Um, you have this acidity that occurs, um, and the it turns out that the it's the hydrogen ion and not the lactate that is effectively poisoning the muscle. It actually prevents the actin and myosin filaments in the muscle from being able to relax. Um, again, for most people, that second lactate threshold, or really third one, depending on how you're counting them, um, occurs somewhere between four and five millimole of lactate. Again, that can be That's that's a much more variable number. Okay. [snorts] So, I'm going to stop there. There's a lot we could talk about there, but I hopefully that kind of sets the groundwork. Very much so. — [snorts] — I think maybe worth clicking on to zone

two before we get further in a little bit of a different way, because that seems like there's been a lot of discussion lately on whether it has unique benefits, whether it's just better to focus on higher intensity work only. So, how do you think about this question? I think it comes down to context. I think there's a lot of confusion around this. So, so I hopefully I'll do my best to dispel that. Um, there's ideas out there challenging the idea that zone two, um, is special or magical or there's anything that's good about it. Um, and there are certainly people who would assert that high intensity work produces the same or even greater adaptations. Um, and I think honestly, in the framework that some people are proposing that, it is true. Okay? So, so let's now sort of think through this um, if you are uh, so so for the proponents of high intensity exercise, people who say don't waste your time doing zone two, um, the shorter the amount of exercise time that a person has, the more true that is. Because remember something I said a few minutes ago, which is if you really want to maximize the area of your triangle, nothing beats volume. Now, can't be volume like walking won't do it. So, you have to have some you have to get to zone two, this first place where you have some adaptation. Um but the more time you spend there, the better. And so, if we're going to talk about a professional athlete or even a recreational athlete, if you're going to talk about uh the way I trained 10 or you know, 10 to 15 years ago, the way I trained, where by some miracle I still was managing to spend 14 to 16 hours a week on a bike, um then we can get into the nuance of how that time should be divided. So, now let's turn this over to kind of someone who's going to adhere to the general guidelines. So, the general guideline says you should exercise uh ideally 150 minutes per week. So, that's 2 and 1/2 hours per week. Um and I'm sure the guidelines would be happy if you did more, but that's what we're trying to get people to, right? Most people are not exercising 2 and 1/2 hours per week. And truthfully, if that's all you can adhere to, then zone two is not going to be an efficient use of your time because it doesn't provide a sufficient enough training stimulus to drive the adaptations to make the triangle bigger. And remember, that 150 minutes is total exercise. Well, part of that's going to have to be some resistance training. So, even if you said, "I'm going to carve out an hour uh for two 30-minute resistance training workouts a week. " Then you've got an hour and a half for cardio. You know, truthfully, I would say then all of that time should be done at high intensity. You should probably have two 45-minute high intensity workouts. Um but when I talk about training, I'm not and maybe I should be, but I'm generally not talking to that population. When I'm talking to my patients in that population, it's a different story. And we do. We're very clear that you know, if you've only got 2 and 1/2 hours this week to exercise, we're going to craft your program around that. Um but I'm sort of talking to a person who is really thinking about how to optimize and achieve their best results over, you know, both lifespan and healthspan over decades. And if that's the case, then you're going to need more volume than 150 minutes a week. And then that means you're going to have to utilize different levels of intensity. So, because zone two is this point at which lactate rises to the level where it's now in the bloodstream. Um so, local tissues can't clear it, uh but your body is able to clear it. You're stressing this system. This is the first place where you're now really stressing the system enough to recruit more glycolytic fibers. But what's nice about this is the intensity is low enough that you can keep going for a long enough period of time. And this is why endurance athletes who are training for you know, 15 to 20 hours a week are indeed spending basically 80% of their time in this zone because the intensity is low enough that they can do it for so long, and yet they are still getting a training adaptation. So, if you are training in zone two, while you're not getting as much adaptation as you're getting at zone five, uh you're still applying a strong enough training stimulus to activate muscle uh sorry, both fuel systems, right? So, you're you know, you're not maximal, but you're near maximal for fat oxidation. You have some glycolysis. You have lactate shuttle, but you don't have the wear and tear of the acidity and the fatigue that comes when lactate production completely overwhelms clearance uh systemically. So, again, you can pack in volume of training um in a way that you can't with very high intensity. Um there are other benefits to zone two, by the way, if you're an athlete, which is it comes with the improved um with the benefits of improved movement efficiency. Um I discussed this um you know, on a on a podcast as well. So, um I guess I hope that clarifies kind of the context around uh one versus the other.

And in looking in terms of like spending more time than the bare minimum when it comes to exercise, how does then exercise intensity play a role into the relationship of volume and sustainability? So, once you're not constrained by that 150 minutes per week, and honestly, that's my hope. My hope is that everybody listening to us right now, even though once in a while they might be constrained by that, but that they can find more time to exercise. Um the limiting factors start to become fatigue and recoverability, uh and even to some extent adherence. And I think that that's especially as you get older, fatigue and recoverability become real limiting factors. So, again, higher intensity workout uh workout in zone five uh very important, um and should always be a part of your training. You can't do that much of it once you get into your 40s and 50s. Uh again, when you're in your 20s and even into your 30s, you can still hammer these workouts. Um but I you know, I can't do those workouts three or four times a week anymore. Um and I don't think most people listening right now can, either. So, um if you're going to be able to devote more time to your training, you're going to have to be able to um do so at a lower physiologic cost. And again, volume drives adaptation. That's the thing to remember. It's volume above all else that's driving adaptation, provided that volume is at least at zone two, where you start to um undergo all those changes we discussed. So, um basically, there's a you know, uh you know, there's a cost of doing high intensity work. And by the way, part of that is adherence-based. Um it's more painful, it's more fatiguing, and it's harder to sustain. Um so, uh you know, one of the things I tell patients who are bored when they're doing zone two is, "Look, use it as an opportunity to get really caught up on your favorite podcast or your favorite audiobook or something like that. " Um something that frankly is a little bit harder to do during a high intensity workout, where you're probably not as able to to concentrate better. So, taking it back to, you know, basically the critics of zone two, um they're correct in a narrow sense in that per unit time, high intensity training delivers more physiologic adaptation, um but they're kind of wrong in the way that it matters. It's not that zone two is magical, it's that it's practical. And it becomes more and more uh valuable as your volume increases. So, in short, um I think zone two is the cornerstone that lets you do enough work, enough volume safely and consistently, so that you get the adaptations you need to be an athlete for life. Moving on now to look at how someone can measure zone two and VO2 max, understand what they are. Um when is it useful? How do you go about measuring it? And let's start with zone two, just because we were on that thread. Thank you for viewing this sneak peek of an Ask Me Anything episode of The Drive. As a premium member, you'll get immediate access to the full AMA episode you just watched a sneak peek for, our entire back catalog of AMA episodes, and all future AMA episodes. — You'll get longevity-focused premium articles packed with actionable insights. You'll get unrivaled show notes for each and every episode of The Drive, and much more. Become a premium member today at peterattiamd. com/subscribe. — Oh. —