#379 - AMA #79： A guide to cardiorespiratory training at any fitness level to improve healthspan, lifespan, and long-term independence
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Summary
In today's AMA, we take a comprehensive look at cardiorespiratory fitness, one of the most common topics we get asked about, and of course, an area that is central to not only lifespan, but also healthspan. We'll discuss why cardioreticism is a modophile predictor of healthspan, what zone two actually represents, and why it's different from higher intensity work. And as always, I'll include any updated thoughts on topics, something which of course I'm constantly updating my thinking on topics and hopefully sharpening it.
Transcript
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Hey everyone, welcome to a sneak peek, ask me anything or AMA episode of the drive podcast.
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I'm your host, Peter Atiyah. At the end of this short episode, I'll explain how you can access
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the AMA episodes in full, along with a ton of other membership benefits we've created,
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or you can learn more now by going to peteratiyahmd.com forward slash subscribe.
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So without further delay, here's today's sneak peek of the ask me anything episode.
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Welcome to ask me anything AMA episode 79. In today's AMA, we take a comprehensive look at
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cardiorespiratory fitness. One of the most common topics we get questions about, and of course,
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an area that is central to not only lifespan, but also healthspan. Now, look, we've done a lot of
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content on this topic, but we wanted to put together an episode that brought it all together
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in one place. And as always, to include any of my updated thoughts, something which of course,
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I'm constantly updating my thinking on topics and hopefully sharpening it. So the goal of this
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episode is to provide a practical guide that allows you to structure your training in a way that
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meaningfully impacts your health, your functional capacity, and maintains independence as you age.
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We'll discuss why cardiorespiratory fitness is one of the strongest modophile predictors of
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healthspan and lifespan, what zone two training actually represents and why it's different from
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higher intensity work. And there seems to be still some confusion about this, how to think about
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exercise volume, intensity, and the practicality of training in different zones and using different
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approaches, how to measure and track improvements in zone two specifically, VO2 max targets, age adjusted
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goals, and planning for the marginal decade, structuring an effective workout routine around your zone
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two goals and your VO2 max goals, how to balance zone two with higher intensity work across varying
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weekly training volumes. Again, this is a very important part of the discussion because as I
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allude to, there are going to be some of you listening to this that shouldn't be doing zone
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two at all. And my hope is that by the end of this podcast, you've been able to identify
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yourselves. Adjusting training for beginners, metabolically unhealthy individuals, long-time
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trainees, older adults, et cetera. Specific considerations for women specifically, including some
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misconceptions around zone two or other forms of cardio training, common training mistakes
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and how to avoid plateaus, burnout, and mis-targeted intensities. Practical strategies for sustainability,
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progression, and long-term adaptation. If you're a subscriber and you want to watch the full video
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of this podcast, you can find it on the show notes page. And if you're not a subscriber, you
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can watch a sneak peek at the video on our YouTube page. So without further delay, I hope you enjoy AMA 79.
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Peter, welcome to another AMA. How are you doing?
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I'm doing very well. Thank you for having me back.
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Always welcome to have you. I see every time we do these, you bring something more and more to each recording.
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What have I brought this time? I don't know. I'm not even aware.
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Nothing you can think of. Nothing jumps out. No new additions to the body.
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No, but given that we've now introduced carve-outs at the end of these, it's made me that much more aware
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of how much I am the perfect target of YouTube and Instagram ads because I could create an entire
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podcast called The Carve-Out where I just talk about the things that I buy when they're served up
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to me as ads that I end up liking. Have you bought one thing today?
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Not today, but I did get something really awesome two days ago. It arrived two days ago.
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Heck no. I'm saving it for a carve-out maybe next month. I put these things to the test. Let me tell
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you, I am a serious tester of product. So the thing that I got so far, I've already tested it
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once. It was insanely good. I need a few more reps with it. And if I'm still digging it in a month,
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That's great. It's exciting because I don't think people realize what you're talking about
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could be a legitimate thing that is actually beneficial to health and longevity.
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And it could be the dumbest $20 gadget that has ever existed. And we have no way of knowing which
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Well, I'll give you a hint. It was served up on a YouTube ad, so it's definitely not the former,
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Yes. You just tend to live on the spectrums though, right? Like you kind of go one or the
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The only thing you do in moderation is moderation, which turns out is the same with engaging in
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YouTube and Instagram ads. You like to go all in. So with that said, what we're covering today,
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one topic, cardiorespiratory fitness, in simpler terms for people, zone two VO2 max. This is a topic
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we have talked about over the years on different podcasts, different guests, different articles,
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but it's also a topic that we get asked about by far the most, partly because of the interest in
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it. And also I think because of how open you are on how it is the biggest and strongest modifiable
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predictor of both healthspan and lifespan, meaning it's the biggest impact that someone can do
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something about it. So that's why we decided to kind of dedicate this AMA, gather all the questions
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and try to make it a one-stop shop for everything relating to how to measure, track, improve zone
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two VO2 max through training. We'll cover how this relates to people who have a lot of time to work
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out, people who have a little time to work out. We'll look at how it relates to people who are just
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starting training, people who have been training for a long time, older adults, if anything changes
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for women in particular and more. We'll also look at if your opinion has evolved around some recent
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debates and discussions around zone two lactate, how to balance volume and intensity with the goal
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of not having your best exercise month ever and then stopping, but more so long-term. So with all
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that said, anything else you want to add before we get started? Yes. This was an idea that when the
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team pitched it to me, my initial response was, I don't think this is worth it. We've already
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generated plenty of content on this. It certainly would be within the top five things that I talk
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about. And the team, I think, was able to get me convinced, and I believe rightly so, by saying,
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yeah, Peter, that's kind of the point, is if someone were to try to go out there and aggregate
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everything you've said on this topic, it would be a full-time job. And I think someone even shared
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with me how many hours and hours of content it would be, and it was triple-digit hours. And they said,
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that's great for the person with an encyclopedic memory who is a lifelong devotee who doesn't have
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a job, but most people aren't going to fit into that category. And it would be really helpful to
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have a practical guide, not just a theoretical guide to this. That kind of won me over. And so
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I guess I would just say kudos to the team for convincing me that this was the way to do it.
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I'm really happy with the way they've crafted a story around this. Let's dive in.
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Before we do, a quick question. Do you think if the team started to put their arguments
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in forms of videos that we ran as Instagram or YouTube ads, you'd be more willing to listen?
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If you could be good enough, but you have to catch me within the first 10 seconds of the ad,
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or I'm skipping it. Like, I don't know that that's a skill set that exists on our team. We don't
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practice that skill of catch you in the first 10 seconds.
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No, we practice more of, we will get you at the end of two hours after explaining in rigor.
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So with that said, I think what would be helpful to start is looking at real quick,
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why is cardiorespiratory fitness a central pillar and not only your approach to lifespan,
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how long you live, but healthspan? Yeah. So again, if you've been listening to me
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talk about this for years, you can literally go to your podcast player and hit forward for
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a couple of minutes. You don't need to hear this, but I do want to spend at least a minute on this
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idea that cardiorespiratory fitness is one of the most important and modifiable
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it's very important that we're talking about modifiable predictors of both how long you're
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going to live and how well you're going to live. So if you look at all the predictors of all-cause
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mortality, which remember that's the holy grail metric of longevity, cardiorespiratory fitness
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outperforms every other variable we can measure. This includes blood pressure. This includes
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cholesterol. This includes BMI, smoking. It even includes age, which just blows my mind.
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So cardiorespiratory fitness, CRF, represents how efficiently your heart and lungs and blood
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vessels and muscles can work together to deliver and utilize oxygen. So the more efficient that system
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is, the more physiologic reserve your body has. And it's this reserve that allows you to tolerate
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stress. This stress can come in the form of an infection, a surgery, or just frankly,
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the day-to-day demands of living. This has been most typically and most repeatedly measured
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using a test called VO2 max. You've heard me talk about this, of course, and it's become a very popular
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thing that people talk about. It's the maximum rate at which the body can utilize oxygen, tested,
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of course, during maximal efforts, which require exercise. So this number is expressed in milliliters
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of oxygen per kilogram of body weight per minute, but it can be estimated using something called
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METs or metabolic equivalents, where one MET is equal to 3.5 milliliters per kilogram per minute
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of oxygen uptake or utilization. So I would say that the reason that VO2 max has become such a popular
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way to do this is because it is a standardized test. That doesn't mean it's always done correctly.
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And we've got plenty of examples of how this can be done incorrectly, which is why for our patients,
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we actually do the test. We got tired of relying on other labs to do it. But for the most part,
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a well-trained technician can do this consistently. And that makes it easy to study. And that's why in
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the literature, you're going to see so much discussion where it comes down to METs or VO2 max,
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the two can be used interchangeably. And you won't, for example, see that when it comes to zone
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two. So we're going to talk a lot about that today, but I just want to point out zone two is a much
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more difficult area to navigate because it's not a maximal effort. It's an in-between effort. VO2 max
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is a maximal effort. So when you tell somebody to basically floor it until they're going to keel
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over, that's actually much easier to achieve. Now, to put some context around the importance of VO2 max
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and mortality, again, because it's been studied, if you're in the bottom quartile or quintile,
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so bottom 20 to 25% of the population with respect to your VO2 max, you've got a four to five-fold
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higher risk of mortality, all-cause mortality in any given year than those in the top 3%, 2% to 3%.
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That's a pretty big jump. But keep in mind, even tiny little jumps, say moving from the second
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quartile to the third quartile, we'll still have easily a 50% to 75% improvement in all-cause
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mortality. So why is this such a powerful relationship? And I think it comes down to
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not just what the number represents, which is everything I've talked about vis-a-vis oxygen
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delivery and utilization. I've said this before, but I think it bears repeating. Measures like VO2 max,
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just like strength, they're actually integrators of work done. So if a person has a VO2 max that is low
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and their aspiration is to have a very high VO2 max, they can, but it will take potentially years
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and countless hours of work done. And that work will be done at the level of their cardiovascular
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system, their pulmonary system, their hematologic system, muscular system, metabolic system. And all of
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those things will have to work and work and work for hundreds of hours to get a desired outcome.
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And if you think about that, that's much more, frankly, impressive from a physiologic perspective
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than taking a pill that lowers your cholesterol. It's not to say that taking a pill that lowers
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your cholesterol doesn't improve outcomes, but it's not going to come close to improving outcomes
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as much as this does on average. There are edge cases. There are some individuals with
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familial hypercholesterolemia where that pill that lowers their cholesterol will have an outsized
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benefit. But by and large, this is why things that improve cardiorespiratory fitness or strength
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tend to have such an impact on mortality. Beyond mortality, can you also talk about the
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health span benefits? So what you refer to as not only how long it can help you live,
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Yeah. I think the argument here is just as strong. Of course, the data are not quite as
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objective because health span is not as objective. So what I might aspire to be able to do that would
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define good health span for me might not be the same as you, Nick, and is not going to be the same
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as every person that is listening to us right now. But what we do know, and I think we'll show at least
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one figure to that effect today, is that VO2 max declines quite predictably with age at about 10% per
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decade. But the oxygen cost of doing things doesn't change. So whether it be climbing stairs or
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lifting something up or chasing your kids around or playing a sport, those things don't change. So
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if you have a declining capacity to deliver and utilize oxygen in the presence of constant demand,
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at some point those curves cross. And what that effectively means is you start losing the ability
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to do these things. Again, we'll talk about this in much more detail when we get there. But as I think
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a figure can represent better than what I'm saying necessarily, our objective is to be able to maintain
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optionality around being physical for as long as possible. And that is tantamount to having as high
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a VO2 max as possible, in addition to being as strong as possible.
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When talking about cardiorespiratory fitness in the past, to kind of help people understand it in a
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simpler way, you've often talked about the base and peak model. Can you just walk through a little
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bit more about that framework and how different exercise and intensities can contribute to each
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I talk about this cardiorespiratory fitness triangle, and I can't take credit for this at all. It was one of
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my cycling coaches that came up with this. So the idea was that you picture a triangle with a base
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and a peak. And the base is what we think of as your capacity to do sustained sub-maximal effort
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over a long period of time. So think of something you could do for hours. And then the peak represents
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your maximum aerobic output. So what you could sustain for five to 10 minutes. Obviously there are
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so many gradations here. Your functional threshold power, which is what you could obtain for an hour,
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is obviously smaller number than the peak and a shorter number than the base. So anyway, the goal
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here, if you're trying to maximize your total aerobic capacity, is to maximize the area of this
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cardiorespiratory triangle. And of course, to do that, you want to have the widest base and the highest
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peak possible. And these require different forms of training. So if you just trained at one intensity
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level the whole time, you would increase both of these things. I want to be clear on that point
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because it creates so much confusion. If you only parked yourself at one level of training, you would,
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through enough volume, increase both of these. But that's not the way to maximize the problem. And
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it's certainly not the most time efficient way to do it, nor is it necessarily the best way to do it.
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In fact, it's almost assuredly not given the fact that no high level athlete trains that way.
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The base is ideally built through adaptations that help you utilize oxygen more efficiently
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to convert fuel, but mostly fat, into ATP. What this is really geared towards is improving
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mitochondrial density and efficiency and optimizing fat oxidation and lactate utilization.
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Conversely, the peak, which again is that VO2 max, represents the ceiling for oxygen delivery,
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primarily, but utilization. And it's driven by how well this system can deliver oxygen
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to the mitochondria. That's primarily the bottleneck. It's how much oxygen can you deliver
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to mitochondria versus the base, which is how much can you utilize substrate efficiently.
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So when it comes to delivering oxygen to the mitochondria, there are really four big drivers.
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There's the diffusion of oxygen from the lungs into the blood. There's cardiac output. So that's
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heart rate and stroke volume. Then there's the oxygen carrying capacity of the blood, namely hemoglobin.
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And then there's the muscle's ability to extract this. But as I said a moment ago, it's the cardiac
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output that is the main driver here. And it is the one we are most sensitive to in reduction. So again,
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what drives cardiac output primarily is stroke volume, how much blood comes out of the heart with
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each pump and heart rate. And of course, when you're at a VO2 max effort, you're getting to maximum
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heart rate. So somewhere between 70 and 85% of the variability in VO2 max is accounted for just by
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this one variable. In the show notes, we'll include a whole bunch more detail on this if anybody kind of
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wants to nerd out on this stuff. I love this stuff, but I don't want to spend any more time on it right
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here. So as I kind of alluded to, it's very tempting to, and I want to apologize if I've ever
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created the impression or oversimplified this. And it's possible that I have. Zone two is what you do
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exclusively to build your base and high intensity workouts is the only thing you do to build your
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peak. As I said, these systems work together. And if all you did was zone two, you would absolutely
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get a wider base. You would also raise your peak. Similarly, if you did higher intensity training,
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you would increase your peak, but you would also widen your base a little bit. The key, as we'll
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get into in the nuance, is what is the optimized way to utilize time around different volume and
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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,
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which is a big part of what we're going to talk about today. So that's how I think about the
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triangle. When talking about zone two, you've often talked about fat oxidation, mitochondria,
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lactate. Oftentimes, I think these terms can be a little confusing for people. And so I think it's
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always helpful to kind of relook at them and explain it. So do you mind just spending a few
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minutes walking through the cellular mechanisms that are involved in cardiorespiratory fitness, just so
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everyone is kind of familiar with the terms you may or may not use throughout here?
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Yeah. So it's really funny because I've noticed some amazing memes on Instagram where you basically
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have people that are making fun of anybody that uses the word mitochondria. So somehow,
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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.
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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
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mitochondria, inflammation, gut biome, like they've got all the buzzwords.
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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
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system are these organelles called mitochondria. And of course, all of you who took a high school
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class in biology will remember that they're referred to as sort of the little power units
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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.
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The mitochondria can generate ATP from either fatty acids or pyruvate. Pyruvate is a intermediary
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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?
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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
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