The Peter Attia Drive - January 12, 2026


#379 - AMA #79： A guide to cardiorespiratory training at any fitness level to improve healthspan, lifespan, and long-term independence


Episode Stats

Length

38 minutes

Words per Minute

174.58888

Word Count

6,724

Sentence Count

373

Misogynist Sentences

1

Hate Speech Sentences

1


Summary


Transcript

00:00:00.000 Hey everyone, welcome to a sneak peek, ask me anything or AMA episode of the drive podcast.
00:00:15.820 I'm your host, Peter Atiyah. At the end of this short episode, I'll explain how you can access
00:00:20.280 the AMA episodes in full, along with a ton of other membership benefits we've created,
00:00:24.900 or you can learn more now by going to peteratiyahmd.com forward slash subscribe.
00:00:30.600 So without further delay, here's today's sneak peek of the ask me anything episode.
00:00:38.940 Welcome to ask me anything AMA episode 79. In today's AMA, we take a comprehensive look at
00:00:45.060 cardiorespiratory fitness. One of the most common topics we get questions about, and of course,
00:00:49.200 an area that is central to not only lifespan, but also healthspan. Now, look, we've done a lot of
00:00:53.840 content on this topic, but we wanted to put together an episode that brought it all together
00:00:58.320 in one place. And as always, to include any of my updated thoughts, something which of course,
00:01:05.100 I'm constantly updating my thinking on topics and hopefully sharpening it. So the goal of this
00:01:09.420 episode is to provide a practical guide that allows you to structure your training in a way that
00:01:13.760 meaningfully impacts your health, your functional capacity, and maintains independence as you age.
00:01:19.300 We'll discuss why cardiorespiratory fitness is one of the strongest modophile predictors of
00:01:23.260 healthspan and lifespan, what zone two training actually represents and why it's different from
00:01:27.760 higher intensity work. And there seems to be still some confusion about this, how to think about
00:01:31.900 exercise volume, intensity, and the practicality of training in different zones and using different
00:01:37.460 approaches, how to measure and track improvements in zone two specifically, VO2 max targets, age adjusted
00:01:43.420 goals, and planning for the marginal decade, structuring an effective workout routine around your zone
00:01:49.740 two goals and your VO2 max goals, how to balance zone two with higher intensity work across varying
00:01:55.700 weekly training volumes. Again, this is a very important part of the discussion because as I
00:02:00.880 allude to, there are going to be some of you listening to this that shouldn't be doing zone
00:02:04.400 two at all. And my hope is that by the end of this podcast, you've been able to identify
00:02:07.480 yourselves. Adjusting training for beginners, metabolically unhealthy individuals, long-time
00:02:11.720 trainees, older adults, et cetera. Specific considerations for women specifically, including some
00:02:16.960 misconceptions around zone two or other forms of cardio training, common training mistakes
00:02:22.060 and how to avoid plateaus, burnout, and mis-targeted intensities. Practical strategies for sustainability,
00:02:27.980 progression, and long-term adaptation. If you're a subscriber and you want to watch the full video
00:02:31.760 of this podcast, you can find it on the show notes page. And if you're not a subscriber, you
00:02:36.000 can watch a sneak peek at the video on our YouTube page. So without further delay, I hope you enjoy AMA 79.
00:02:46.960 Peter, welcome to another AMA. How are you doing?
00:02:51.840 I'm doing very well. Thank you for having me back.
00:02:54.460 Always welcome to have you. I see every time we do these, you bring something more and more to each recording.
00:03:02.340 What have I brought this time? I don't know. I'm not even aware.
00:03:05.300 Nothing you can think of. Nothing jumps out. No new additions to the body.
00:03:10.420 No, but given that we've now introduced carve-outs at the end of these, it's made me that much more aware
00:03:18.280 of how much I am the perfect target of YouTube and Instagram ads because I could create an entire
00:03:26.520 podcast called The Carve-Out where I just talk about the things that I buy when they're served up
00:03:33.240 to me as ads that I end up liking. Have you bought one thing today?
00:03:37.100 Not today, but I did get something really awesome two days ago. It arrived two days ago.
00:03:43.260 Anything you'd like to share with a group?
00:03:44.800 Heck no. I'm saving it for a carve-out maybe next month. I put these things to the test. Let me tell
00:03:49.580 you, I am a serious tester of product. So the thing that I got so far, I've already tested it
00:03:55.420 once. It was insanely good. I need a few more reps with it. And if I'm still digging it in a month,
00:04:02.240 it might make it to the carve-out list.
00:04:03.660 That's great. It's exciting because I don't think people realize what you're talking about
00:04:08.700 could be a legitimate thing that is actually beneficial to health and longevity.
00:04:14.460 And it could be the dumbest $20 gadget that has ever existed. And we have no way of knowing which
00:04:21.080 one it is when it comes to that spectrum.
00:04:22.980 Well, I'll give you a hint. It was served up on a YouTube ad, so it's definitely not the former,
00:04:32.020 but I will say it's also not the latter.
00:04:36.160 Leaving people hanging.
00:04:37.380 There's a lot of daylight between those two.
00:04:39.540 Yes. You just tend to live on the spectrums though, right? Like you kind of go one or the
00:04:43.660 other.
00:04:44.600 That's fair.
00:04:45.200 The only thing you do in moderation is moderation, which turns out is the same with engaging in
00:04:49.840 YouTube and Instagram ads. You like to go all in. So with that said, what we're covering today,
00:04:56.640 one topic, cardiorespiratory fitness, in simpler terms for people, zone two VO2 max. This is a topic
00:05:04.400 we have talked about over the years on different podcasts, different guests, different articles,
00:05:09.440 but it's also a topic that we get asked about by far the most, partly because of the interest in
00:05:15.780 it. And also I think because of how open you are on how it is the biggest and strongest modifiable
00:05:22.380 predictor of both healthspan and lifespan, meaning it's the biggest impact that someone can do
00:05:27.660 something about it. So that's why we decided to kind of dedicate this AMA, gather all the questions
00:05:33.260 and try to make it a one-stop shop for everything relating to how to measure, track, improve zone
00:05:40.920 two VO2 max through training. We'll cover how this relates to people who have a lot of time to work
00:05:46.420 out, people who have a little time to work out. We'll look at how it relates to people who are just
00:05:50.580 starting training, people who have been training for a long time, older adults, if anything changes
00:05:55.680 for women in particular and more. We'll also look at if your opinion has evolved around some recent
00:06:01.500 debates and discussions around zone two lactate, how to balance volume and intensity with the goal
00:06:08.340 of not having your best exercise month ever and then stopping, but more so long-term. So with all
00:06:14.940 that said, anything else you want to add before we get started? Yes. This was an idea that when the
00:06:22.700 team pitched it to me, my initial response was, I don't think this is worth it. We've already
00:06:28.720 generated plenty of content on this. It certainly would be within the top five things that I talk
00:06:34.020 about. And the team, I think, was able to get me convinced, and I believe rightly so, by saying,
00:06:40.360 yeah, Peter, that's kind of the point, is if someone were to try to go out there and aggregate
00:06:44.960 everything you've said on this topic, it would be a full-time job. And I think someone even shared
00:06:49.880 with me how many hours and hours of content it would be, and it was triple-digit hours. And they said,
00:06:55.900 that's great for the person with an encyclopedic memory who is a lifelong devotee who doesn't have
00:07:02.100 a job, but most people aren't going to fit into that category. And it would be really helpful to
00:07:06.680 have a practical guide, not just a theoretical guide to this. That kind of won me over. And so
00:07:12.540 I guess I would just say kudos to the team for convincing me that this was the way to do it.
00:07:16.660 I'm really happy with the way they've crafted a story around this. Let's dive in.
00:07:20.320 Before we do, a quick question. Do you think if the team started to put their arguments
00:07:24.560 in forms of videos that we ran as Instagram or YouTube ads, you'd be more willing to listen?
00:07:30.700 If you could be good enough, but you have to catch me within the first 10 seconds of the ad,
00:07:35.040 or I'm skipping it. Like, I don't know that that's a skill set that exists on our team. We don't
00:07:39.380 practice that skill of catch you in the first 10 seconds.
00:07:42.320 No, we practice more of, we will get you at the end of two hours after explaining in rigor.
00:07:47.900 So with that said, I think what would be helpful to start is looking at real quick,
00:07:53.720 why is cardiorespiratory fitness a central pillar and not only your approach to lifespan,
00:08:00.920 how long you live, but healthspan? Yeah. So again, if you've been listening to me
00:08:04.980 talk about this for years, you can literally go to your podcast player and hit forward for
00:08:09.120 a couple of minutes. You don't need to hear this, but I do want to spend at least a minute on this
00:08:13.260 idea that cardiorespiratory fitness is one of the most important and modifiable
00:08:17.720 it's very important that we're talking about modifiable predictors of both how long you're
00:08:22.400 going to live and how well you're going to live. So if you look at all the predictors of all-cause
00:08:27.960 mortality, which remember that's the holy grail metric of longevity, cardiorespiratory fitness
00:08:33.460 outperforms every other variable we can measure. This includes blood pressure. This includes
00:08:39.360 cholesterol. This includes BMI, smoking. It even includes age, which just blows my mind.
00:08:46.240 So cardiorespiratory fitness, CRF, represents how efficiently your heart and lungs and blood
00:08:52.220 vessels and muscles can work together to deliver and utilize oxygen. So the more efficient that system
00:08:58.820 is, the more physiologic reserve your body has. And it's this reserve that allows you to tolerate
00:09:06.080 stress. This stress can come in the form of an infection, a surgery, or just frankly,
00:09:12.500 the day-to-day demands of living. This has been most typically and most repeatedly measured
00:09:18.440 using a test called VO2 max. You've heard me talk about this, of course, and it's become a very popular
00:09:25.040 thing that people talk about. It's the maximum rate at which the body can utilize oxygen, tested,
00:09:32.640 of course, during maximal efforts, which require exercise. So this number is expressed in milliliters
00:09:38.960 of oxygen per kilogram of body weight per minute, but it can be estimated using something called
00:09:44.940 METs or metabolic equivalents, where one MET is equal to 3.5 milliliters per kilogram per minute
00:09:53.880 of oxygen uptake or utilization. So I would say that the reason that VO2 max has become such a popular
00:10:01.480 way to do this is because it is a standardized test. That doesn't mean it's always done correctly.
00:10:06.380 And we've got plenty of examples of how this can be done incorrectly, which is why for our patients,
00:10:11.880 we actually do the test. We got tired of relying on other labs to do it. But for the most part,
00:10:17.260 a well-trained technician can do this consistently. And that makes it easy to study. And that's why in
00:10:23.380 the literature, you're going to see so much discussion where it comes down to METs or VO2 max,
00:10:30.920 the two can be used interchangeably. And you won't, for example, see that when it comes to zone
00:10:36.420 two. So we're going to talk a lot about that today, but I just want to point out zone two is a much
00:10:41.080 more difficult area to navigate because it's not a maximal effort. It's an in-between effort. VO2 max
00:10:47.120 is a maximal effort. So when you tell somebody to basically floor it until they're going to keel
00:10:51.960 over, that's actually much easier to achieve. Now, to put some context around the importance of VO2 max
00:10:57.300 and mortality, again, because it's been studied, if you're in the bottom quartile or quintile,
00:11:03.380 so bottom 20 to 25% of the population with respect to your VO2 max, you've got a four to five-fold
00:11:11.000 higher risk of mortality, all-cause mortality in any given year than those in the top 3%, 2% to 3%.
00:11:19.080 That's a pretty big jump. But keep in mind, even tiny little jumps, say moving from the second
00:11:26.760 quartile to the third quartile, we'll still have easily a 50% to 75% improvement in all-cause
00:11:32.880 mortality. So why is this such a powerful relationship? And I think it comes down to
00:11:39.400 not just what the number represents, which is everything I've talked about vis-a-vis oxygen
00:11:44.400 delivery and utilization. I've said this before, but I think it bears repeating. Measures like VO2 max,
00:11:50.680 just like strength, they're actually integrators of work done. So if a person has a VO2 max that is low
00:11:58.920 and their aspiration is to have a very high VO2 max, they can, but it will take potentially years
00:12:06.580 and countless hours of work done. And that work will be done at the level of their cardiovascular
00:12:12.740 system, their pulmonary system, their hematologic system, muscular system, metabolic system. And all of
00:12:19.240 those things will have to work and work and work for hundreds of hours to get a desired outcome.
00:12:25.460 And if you think about that, that's much more, frankly, impressive from a physiologic perspective
00:12:31.880 than taking a pill that lowers your cholesterol. It's not to say that taking a pill that lowers
00:12:35.760 your cholesterol doesn't improve outcomes, but it's not going to come close to improving outcomes
00:12:39.860 as much as this does on average. There are edge cases. There are some individuals with
00:12:45.820 familial hypercholesterolemia where that pill that lowers their cholesterol will have an outsized
00:12:51.140 benefit. But by and large, this is why things that improve cardiorespiratory fitness or strength
00:12:57.500 tend to have such an impact on mortality. Beyond mortality, can you also talk about the
00:13:03.340 health span benefits? So what you refer to as not only how long it can help you live,
00:13:08.740 but how well it can help you live.
00:13:10.140 Yeah. I think the argument here is just as strong. Of course, the data are not quite as
00:13:14.720 objective because health span is not as objective. So what I might aspire to be able to do that would
00:13:21.180 define good health span for me might not be the same as you, Nick, and is not going to be the same
00:13:25.580 as every person that is listening to us right now. But what we do know, and I think we'll show at least
00:13:31.400 one figure to that effect today, is that VO2 max declines quite predictably with age at about 10% per
00:13:39.220 decade. But the oxygen cost of doing things doesn't change. So whether it be climbing stairs or
00:13:45.660 lifting something up or chasing your kids around or playing a sport, those things don't change. So
00:13:51.580 if you have a declining capacity to deliver and utilize oxygen in the presence of constant demand,
00:14:00.260 at some point those curves cross. And what that effectively means is you start losing the ability
00:14:05.480 to do these things. Again, we'll talk about this in much more detail when we get there. But as I think
00:14:12.320 a figure can represent better than what I'm saying necessarily, our objective is to be able to maintain
00:14:19.300 optionality around being physical for as long as possible. And that is tantamount to having as high
00:14:28.740 a VO2 max as possible, in addition to being as strong as possible.
00:14:33.480 When talking about cardiorespiratory fitness in the past, to kind of help people understand it in a
00:14:37.660 simpler way, you've often talked about the base and peak model. Can you just walk through a little
00:14:42.840 bit more about that framework and how different exercise and intensities can contribute to each
00:14:49.300 component of that?
00:14:50.580 I talk about this cardiorespiratory fitness triangle, and I can't take credit for this at all. It was one of
00:14:55.340 my cycling coaches that came up with this. So the idea was that you picture a triangle with a base
00:15:01.340 and a peak. And the base is what we think of as your capacity to do sustained sub-maximal effort
00:15:08.760 over a long period of time. So think of something you could do for hours. And then the peak represents
00:15:16.220 your maximum aerobic output. So what you could sustain for five to 10 minutes. Obviously there are
00:15:23.900 so many gradations here. Your functional threshold power, which is what you could obtain for an hour,
00:15:29.020 is obviously smaller number than the peak and a shorter number than the base. So anyway, the goal
00:15:34.860 here, if you're trying to maximize your total aerobic capacity, is to maximize the area of this
00:15:41.000 cardiorespiratory triangle. And of course, to do that, you want to have the widest base and the highest
00:15:46.800 peak possible. And these require different forms of training. So if you just trained at one intensity
00:15:54.400 level the whole time, you would increase both of these things. I want to be clear on that point
00:16:00.540 because it creates so much confusion. If you only parked yourself at one level of training, you would,
00:16:08.080 through enough volume, increase both of these. But that's not the way to maximize the problem. And
00:16:13.520 it's certainly not the most time efficient way to do it, nor is it necessarily the best way to do it.
00:16:18.480 In fact, it's almost assuredly not given the fact that no high level athlete trains that way.
00:16:23.140 The base is ideally built through adaptations that help you utilize oxygen more efficiently
00:16:29.920 to convert fuel, but mostly fat, into ATP. What this is really geared towards is improving
00:16:38.480 mitochondrial density and efficiency and optimizing fat oxidation and lactate utilization.
00:16:44.960 Conversely, the peak, which again is that VO2 max, represents the ceiling for oxygen delivery,
00:16:51.180 primarily, but utilization. And it's driven by how well this system can deliver oxygen
00:16:57.120 to the mitochondria. That's primarily the bottleneck. It's how much oxygen can you deliver
00:17:03.140 to mitochondria versus the base, which is how much can you utilize substrate efficiently.
00:17:10.300 So when it comes to delivering oxygen to the mitochondria, there are really four big drivers.
00:17:16.420 There's the diffusion of oxygen from the lungs into the blood. There's cardiac output. So that's
00:17:23.180 heart rate and stroke volume. Then there's the oxygen carrying capacity of the blood, namely hemoglobin.
00:17:28.580 And then there's the muscle's ability to extract this. But as I said a moment ago, it's the cardiac
00:17:33.660 output that is the main driver here. And it is the one we are most sensitive to in reduction. So again,
00:17:41.140 what drives cardiac output primarily is stroke volume, how much blood comes out of the heart with
00:17:47.160 each pump and heart rate. And of course, when you're at a VO2 max effort, you're getting to maximum
00:17:51.980 heart rate. So somewhere between 70 and 85% of the variability in VO2 max is accounted for just by
00:17:59.400 this one variable. In the show notes, we'll include a whole bunch more detail on this if anybody kind of
00:18:04.540 wants to nerd out on this stuff. I love this stuff, but I don't want to spend any more time on it right
00:18:08.900 here. So as I kind of alluded to, it's very tempting to, and I want to apologize if I've ever
00:18:15.340 created the impression or oversimplified this. And it's possible that I have. Zone two is what you do
00:18:22.640 exclusively to build your base and high intensity workouts is the only thing you do to build your
00:18:26.860 peak. As I said, these systems work together. And if all you did was zone two, you would absolutely
00:18:34.340 get a wider base. You would also raise your peak. Similarly, if you did higher intensity training,
00:18:39.980 you would increase your peak, but you would also widen your base a little bit. The key, as we'll
00:18:45.540 get into in the nuance, is what is the optimized way to utilize time around different volume and
00:18:54.420 intensity requirements? So how much total work can you do? How much cardiorespiratory fitness training
00:19:02.180 can you do? That's probably the single biggest determinant, but that involves a min-max problem,
00:19:08.980 which is a big part of what we're going to talk about today. So that's how I think about the
00:19:13.180 triangle. When talking about zone two, you've often talked about fat oxidation, mitochondria,
00:19:19.900 lactate. Oftentimes, I think these terms can be a little confusing for people. And so I think it's
00:19:25.020 always helpful to kind of relook at them and explain it. So do you mind just spending a few
00:19:28.900 minutes walking through the cellular mechanisms that are involved in cardiorespiratory fitness, just so
00:19:35.360 everyone is kind of familiar with the terms you may or may not use throughout here?
00:19:38.980 Yeah. So it's really funny because I've noticed some amazing memes on Instagram where you basically
00:19:46.540 have people that are making fun of anybody that uses the word mitochondria. So somehow,
00:19:51.980 because I don't really pay attention to the wellness influencer health space, apparently the word
00:19:57.880 mitochondria is now just one of those buzzwords that you should throw around as much as possible.
00:20:02.760 And so if you're playing sort of wellness influencer bingo, you're going to get a lot
00:20:08.260 of points for mitochondria. Can't remember some of the other awesome words that are just
00:20:12.860 basically pathognomonic for buffoonery. Have you seen any of these memes? They're amazing. It's like
00:20:19.160 mitochondria, inflammation, gut biome, like they've got all the buzzwords.
00:20:25.140 Protein, another one. Protein, I'm sure. You've set me up now to trigger a bingo card. But I guess
00:20:32.360 you're right. You can't have this discussion without doing this. So hopefully I'm going to
00:20:35.840 get an exemption for my use of the word mitochondria here. At the foundation of your cardiorespiratory
00:20:41.940 system are these organelles called mitochondria. And of course, all of you who took a high school
00:20:48.320 class in biology will remember that they're referred to as sort of the little power units
00:20:53.400 of the cell. And the majority of our ATP is produced by them. And again, ATP is the currency
00:21:00.040 for energy. Just because I can't resist giving one more level of detail. The way ATP work is they
00:21:06.240 donate. ATP has three phosphates. They donate one of those phosphates. And it's that liberation of
00:21:12.060 energy that comes from that chemical bond that creates energy.
00:21:16.600 The mitochondria can generate ATP from either fatty acids or pyruvate. Pyruvate is a intermediary
00:21:22.880 breakdown product of glucose via a process called glycolysis. And both of these processes are
00:21:29.160 constantly occurring. It's just the question is, what's the balance in which they're occurring?
00:21:34.020 And of course, are these both equal? No, they're not. Each process has a trade-off. The trade-off
00:21:40.580 would simply be stated this way. If you are optimizing for efficiency and you don't care as
00:21:46.500 much about the speed with which you can deliver ATP, you want to take that more aerobic pathway,
00:21:53.480 meaning utilizing oxygen and shuttling the breakdown product of fatty acid or glucose,
00:22:00.920 either in the form of pyruvate or acetyl-CoA, into the mitochondria to use an oxidative pathway
00:22:06.460 to generate lots of ATP per units of carbon that go in. The problem with that is, as the demand for
00:22:13.420 ATP accelerates, you have to make a trade-off. You have to make a sacrifice. The body says,
00:22:18.320 I'm sorry, I can't do this anymore. I have to go down this quicker path using glycolysis where I turn
00:22:26.100 glucose into pyruvate, ultimately into lactate. I don't get nearly as many ATP for it, but I can
00:22:33.480 deliver much more ATP to the muscle. Now, I can't do this indefinitely. There's a whole problem
00:22:37.740 associated with that, which we'll talk about. But that's effectively at the high level of the trade-off.
00:22:41.620 So another way to think about this is through the lens of the fibers that are involved. And again,
00:22:46.640 these are terms we've used on the podcast before, but the goal of this podcast is to kind of tie
00:22:50.160 this all together. So at lower intensities, you have these type one or slow twitch muscle fibers.
00:22:56.140 And again, I think the term slow twitch, it does to some extent reflect the speed with which they
00:23:00.900 twitch. But I think a more important way to think about them is they're slow to fatigue and they're more
00:23:05.880 endurance-based fibers. So again, at lower intensities, they're the ones that are doing all the work,
00:23:09.900 very rich in mitochondria, deep red. They excel at oxidizing fat, and they're very, very efficient.
00:23:17.080 As the intensity increases, we have to start recruiting more of the type two fibers. These are
00:23:22.960 fast twitch fibers, which again are more contractile in their force, but they are also fast to fatigue.
00:23:30.000 They have less mitochondria, and they're going to recruit and rely more heavily on glycolysis.
00:23:36.260 That's happening outside the mitochondria. So initially, lactate, which again, kind of gets a
00:23:42.560 bit of a bad rap, but again, we've done an entire podcast on this, and we'll link to the podcasts on
00:23:47.180 this topic. But the most important of these is definitely the one with George Brooks. Initially,
00:23:51.600 the lactate gets recycled locally. So it's shuttled to neighboring type one fibers. It gets
00:23:58.940 generated in a type two fiber, gets shuttled to a type one fiber, gets converted back into pyruvate,
00:24:03.860 and then the pyruvate goes into the mitochondria to produce more ATP. That's called the lactate
00:24:09.760 shuttle. But again, these things are constrained by demand, and therefore, as output increases and
00:24:18.980 demand increases, lactate production in the type two fibers begins to exceed the capacity for what can
00:24:26.320 be done locally in the mitochondria adjacent. And at that point, lactate spills into the bloodstream.
00:24:32.100 So if you were measuring lactate in the bloodstream with a continuous lactate monitor, which by the
00:24:36.540 way, these things are easily in prototype, and there's some that are probably in the market,
00:24:40.100 so this would be something you can appreciate in the future. You might start out an exercise session
00:24:43.820 where your lactate is resting at 0.5 millimole. Everything I just described up until this point
00:24:49.340 would not increase that, even though locally lactate levels are rising. But once it starts spilling
00:24:54.840 into the bloodstream, now you actually have to rely on other tissues in the body, the heart,
00:24:59.640 other muscles that are not being utilized at this point in time, they have to start clearing it using
00:25:04.500 lactate as fuel. As we've even learned from George Brooks, the brain will do this as well.
00:25:08.720 The liver also can convert that lactate back into glucose via gluconeogenesis. And this basically
00:25:14.560 allows the body to maintain certain levels of lactate at a new baseline that is above the original
00:25:21.960 baseline. This is usually referred to as the first lactate threshold. And again, for a metabolically
00:25:29.400 healthy individual and someone who's metabolically flexible, meaning they can go back and forth
00:25:34.600 between utilizing glucose and fatty acids, this falls at about 2 millimole of lactate. That is what
00:25:43.200 we refer to as zone 2. Again, if some of those conditions aren't met, if you're not a metabolically
00:25:49.480 flexible person, using that first threshold of lactate at 2 millimole is not going to happen. There
00:25:55.020 are people who walk around at rest with a lactate level above 2. Okay. But the point here is you can
00:26:01.260 maintain, you're now at a new steady state where, if you remember, the first steady state is where the
00:26:09.280 local tissues are able to offset lactate production at the rate that it's being produced. Consumption and
00:26:16.420 production are equal locally. Then you have this second level, which we refer to as the first lactate
00:26:21.220 threshold because it's the first one we're measuring in the plasma. And that's where now the systemic
00:26:25.680 tissues are able to balance it. But now we get to a third level of lactate, which is really called the
00:26:32.140 second lactate threshold. And that's at higher and higher levels. And at this point, once the body gets
00:26:37.240 above that level, and this level varies quite a bit by individual, maybe if we have time, I'll go into
00:26:42.260 how you can measure that. I talked about this at length in the first podcast with Olaf, Alexander, Boo,
00:26:48.200 but we can come back to that. But anyway, at these higher levels of output, glycolytic lactate
00:26:53.220 production in the working muscles completely surpasses the body's ability to clear it. At this
00:26:58.480 point, blood lactate starts to rise much more sharply. It's accompanied by hydrogen ion because
00:27:02.940 the lactate is negatively charged. The hydrogen is positively charged. So they're balanced kind of
00:27:07.540 one-to-one. You have this acidity that occurs. It turns out that it's the hydrogen ion and not the
00:27:13.400 lactate that is effectively poisoning the muscle. It actually prevents the actin and myosin
00:27:18.000 filaments in the muscle from being able to relax. Again, for most people, that second lactate
00:27:24.400 threshold, or really third one, depending on how you're counting them, occurs somewhere between
00:27:28.500 four and five millimole of lactate. That's a much more variable number. Okay. So I'm going to stop
00:27:34.680 there. There's a lot we could talk about there, but hopefully that kind of sets the groundwork.
00:27:38.820 Very much so. I think maybe worth clicking on to zone two before we get further in a little bit of
00:27:45.180 a different way because it seems like there's been a lot of discussion lately on whether it has unique
00:27:50.660 benefits, whether it's just better to focus on higher intensity work only. So how do you think
00:27:56.500 about this question? I think it comes down to context. I think there's a lot of confusion around
00:28:02.660 this. So hopefully I'll do my best to dispel that. There's ideas out there challenging the idea that
00:28:07.680 zone two is special or magical or there's anything that's good about it. And there are certainly people
00:28:13.760 who would assert that high intensity work produces the same or even greater adaptations. And I think
00:28:19.680 honestly, in the framework that some people are proposing that it is true. So let's now think
00:28:25.240 through this. For the proponents of high intensity exercise, people who say, don't waste your time
00:28:31.020 doing zone two, the shorter the amount of exercise time that a person has, the more true that is.
00:28:39.200 Because remember something I said a few minutes ago, which is if you really want to maximize the
00:28:46.480 area of your triangle, nothing beats volume. Now walking won't do it. So you have to get to zone two,
00:28:54.560 this first place where you have some adaptation, but the more time you spend there, the better.
00:29:00.180 And so if we're going to talk about a professional athlete or even a recreational athlete,
00:29:05.520 if you're going to talk about 10 to 15 years ago, the way I train, where by some miracle,
00:29:09.800 I still was managing to spend 14 to 16 hours a week on a bike, then we can get into the nuance
00:29:16.360 of how that time should be divided. So now let's turn this over to someone who's going to adhere
00:29:21.680 to the general guidelines. So the general guidelines says you should exercise ideally 150 minutes per
00:29:28.560 week. So that's two and a half hours per week. And I'm sure the guidelines would be happy if you did
00:29:33.100 more, but that's what we're trying to get people to. Most people are not exercising two and a half
00:29:38.000 hours per week. And truthfully, if that's all you can adhere to, then zone two is not going to be an
00:29:45.540 efficient use of your time because it doesn't provide a sufficient enough training stimulus to
00:29:50.760 drive the adaptations to make the triangle bigger. And remember that 150 minutes is total exercise.
00:29:59.680 Well, part of that's going to have to be some resistance training. So even if you said,
00:30:04.380 I'm going to carve out an hour for two 30 minute resistance training workouts in a week, then you've
00:30:10.620 got an hour and a half for cardio. Truthfully, I would say then all of that time should be done
00:30:16.280 at high intensity. You should probably have two 45 minute high intensity workouts. But when I talk
00:30:21.560 about training, and maybe I should be, but I'm generally not talking to that population.
00:30:25.180 When I'm talking to my patients in that population, it's a different story. And we do. We're very clear
00:30:29.960 that if you've only got two and a half hours this week to exercise, we're going to craft your program
00:30:35.500 around that. But I'm talking to a person who is really thinking about how to optimize and achieve
00:30:43.700 their best results over both lifespan and healthspan over decades. And if that's the case, then you're
00:30:51.020 going to need more volume than 150 minutes a week. And then that means you're going to have to utilize
00:30:57.900 different levels of intensity. So because zone two is this point at which lactate rises to the level
00:31:06.380 where it's now in the bloodstream. So local tissues can't clear it, but your body is able to clear it.
00:31:12.660 You're stressing the system. This is the first place where you're now really stressing the system
00:31:17.460 enough to recruit more glycolytic fibers. But what's nice about this is the intensity is low
00:31:23.640 enough that you can keep going for a long enough period of time. And this is why endurance athletes
00:31:29.840 who are training for 15 to 20 hours a week are indeed spending basically 80% of their time in this zone.
00:31:38.380 Because the intensity is low enough that they can do it for so long, and yet they are still getting
00:31:44.180 a training adaptation. So if you are training in zone two, while you're not getting as much
00:31:51.060 adaptation as you're getting at zone five, you're still applying a strong enough training stimulus to
00:31:56.220 activate both fuel systems, right? So you're not maximal, but you're near maximal for fat oxidation.
00:32:02.000 You have some glycolysis, you have lactate shuttle, but you don't have the wear and tear of the acidity
00:32:10.000 and the fatigue that comes when lactate production completely overwhelms clearance systemically.
00:32:16.940 So again, you can pack in volume of training in a way that you can't with very high intensity.
00:32:23.640 There are other benefits to zone two, by the way, if you're an athlete, which is it comes with the
00:32:28.560 benefits of improved movement efficiency. I discussed this on a podcast as well. So I guess I hope that
00:32:35.340 clarifies kind of the context around one versus the other. In looking in terms of spending more time
00:32:41.680 than the bare minimum, when it comes to exercise, how does then exercise intensity play a role into
00:32:49.580 the relationship of volume and sustainability? Once you're not constrained by that 150 minutes per
00:32:55.860 week, and honestly, that's my hope. My hope is that everybody listening to us right now, even though once
00:33:00.160 in a while they might be constrained by that, but that they can find more time to exercise.
00:33:04.060 The limiting factors start to become fatigue and recoverability, and even to some extent adherence.
00:33:10.820 And I think that especially as you get older, fatigue and recoverability become real limiting
00:33:16.620 factors. So higher intensity workout, workout in zone five, very important and should always be a
00:33:24.800 part of your training. You can't do that much of it once you get into your 40s and 50s. When you're in
00:33:31.820 your 20s and even into your 30s, you can still hammer these workouts, but I can't do those workouts three
00:33:39.540 or four times a week anymore. And I don't think most people listening right now can either. So if you're
00:33:46.100 going to be able to devote more time to your training, you're going to have to be able to do so at a
00:33:52.380 lower physiologic cost. And again, volume drives adaptation. That's the thing to remember. It's
00:33:58.280 volume above all else that's driving adaptation, provided that volume is at least at zone two,
00:34:04.260 where you start to undergo all those changes we discussed. So basically there's a cost of doing
00:34:09.600 high intensity work. And by the way, part of that is an adherence based. It's more painful,
00:34:13.760 it's more fatiguing, and it's harder to sustain. So one of the things I tell patients who are bored
00:34:18.720 when they're doing zone two is look, use it as an opportunity to get really caught up on your
00:34:24.160 favorite podcast or your favorite audio book or something like that. Something that frankly is a
00:34:28.520 little bit harder to do during a high intensity workout where you're probably not as able to
00:34:32.400 concentrate rather. So taking it back to basically the critics of zone two, they're correct in a narrow
00:34:38.140 sense in that per unit time, high intensity training delivers more physiologic adaptation,
00:34:45.720 but they're kind of wrong in the way that it matters. It's not that zone two is magical,
00:34:51.980 it's that it's practical and it becomes more and more valuable as your volume increases.
00:35:00.180 So in short, I think zone two is the cornerstone that lets you do enough work, enough volume safely
00:35:07.640 and consistently so that you get the adaptations you need to be an athlete for life.
00:35:14.280 Moving on now to look at how someone can measure zone two and VO2 max, understand what they are.
00:35:21.460 When is it useful? How do you go about measuring it? And let's start with zone two just because we
00:35:26.600 were on that thread. Thank you for listening to today's sneak peek AMA episode of The Drive.
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