in: Fitness, Health & Fitness, Podcast

• Last updated: January 12, 2023

Podcast #860: Get Fit, Not Fried — The Benefits of Zone 2 Cardio

When most people work out, they jump right from a resting state called Zone 1 cardio to Zone 3 cardio. But in skipping over Zone 2 cardio altogether, they miss out on a significant range of benefits to their health, fitness, and overall well-being.

Here to unpack why you need to make the relatively easy yet hugely beneficial form of exercise that is Zone 2 cardio a big part of your life is Alex Viada, a hybrid athlete and coach. We spend the first twenty minutes of this conversation discussing the physiological science of what cardio zones are and what happens in the body as you move from one zone to the next. From there, we turn to the more accessible and practical elements of getting into Zone 2 cardio. Alex shares the easiest way to know if you’re in Zone 2, and we discuss how it can improve heart health, metabolism, sleep, and weight loss, as well as enhance athletic performance, whether you’re into endurance sports or powerlifting. We then get into the amount of Zone 2 cardio you should be getting each week and how to get it, including Alex’s take on the ever-controversial elliptical machine.

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Brett McKay: Brett McKay here, and welcome to another edition of the Art of Manliness podcast. When most people work out, they jump right from a resting state called Zone 1 cardio to Zone 3 cardio, but in skipping over Zone 2 cardio altogether, they miss out on a significant range of benefits to their health, fitness, and overall well-being. Here to unpack why you need to make the relatively easy, yet hugely beneficial form of exercise that is Zone 2 cardio, a big part of your life is Alex Viada, a hybrid athlete and coach. We spend the first 20 minutes of this conversation discussing the physiological science of what cardio zones are and what happens to the body as you move from one zone to the next. From there, we turn into more accessible and practical elements of getting into Zone 2 cardio. Alex shares the easiest way to know if you’re in Zone 2, and we discuss how you can improve you heart health, metabolism, sleep, and weight loss, as well as enhanced athletic performance, whether you’re into endurance sports or powerlifting. We then get into an amount of Zone 2 cardio you should be getting each week and how to get it, including Alex’s take on the ever-controversial elliptical machine. After the show is over, check out our show notes at

 And way we go. Alright, Alex Viada, welcome to the show.

Alex Viada: Hey, thank you so much, Brett, a pleasure to be here.

Brett McKay: So you are the founder of Complete Human Performance. This is an educational website where you provide education and courses on physical fitness, and nutrition, but you also provide coaching for triathletes, powerlifters, you’ve done some coaching for special operations guys. Let’s talk a bit about your background, how did you end up doing this where you’re coaching not only triathletes, but powerlifters, but also there’s powerlifting triathletes as well. What’s the story there?

Alex Viada: Yeah, so I guess the story there, I’d have to back up quite a bit, and I’ll try to keep this brief and to the relevant points. So back when I first started getting back into strength training shortly after college, I was very much of the powerlifting strength at all costs mentality, and it wasn’t until about 2007 when I first got talked into running a 5K and really coming close to having the walls close in on me and my first training run and realizing I was out of shape, that I really realized that there was kind of this gaping hole in my fitness. And it was really the process of going from a powerlifting background, strength training background, to wanting to learn how to not just be cardiovascularly survivable, but actually, be really cardiovascularly fit. And kind of at the time, and we’re talking mid-2000s, the strength training and endurance training communities were very much split. There was the whole strength conceit of cardio is anything more than five reps and you go into endurance training and very much the mindset among a lot of coaches back in that day was still that strength training was something you could do, and that the strength training programs are absolutely horrible.

I mean, I remember going through my USAT certification, USA Triathlon, and this strength training was… We’re talking about people doing bodyweight lunges for sets of 20 to 25, it was really bad. And part of that whole process, that experience, and realizing that if I wanted to be a powerlifter who was really good at running, I wasn’t gonna be able to talk to any powerlifting coaches about running, and I wasn’t gonna be able to talk to any running coaches about powerlifting, I kinda had to develop a lot of this on my own, and that was actually part of what went into the whole… When I wrote the Hybrid Athlete, that was part of what prompted that entire concept, that hybrid training concept, was being able to apply elite-level endurance training methodology to powerlifters and using the really depth of understanding of the “opposite sport” to really whittle out and get rid of all the noise and nonsense, and prescribe to strength athletes what is the absolute minimum most effective dose of endurance training to get results and vice versa.

So really taking lessons from the opposite side of the aisle, so to speak, and using that to optimize training for everybody, and that methodology, honestly, when I… In 2012, 2013, before the book came out, and then in 2014, and 2015, I really, really caught a lot of people’s attention, I think. There are a lot of people who… They love strength training, they love the process, but at the time they were going, “I don’t like the fact that I gave up all of this running,” or, “I’m a powerlifter who’s been doing this for years, and I feel a little beat up. I want to try something different. I don’t know, maybe I wanna do a triathlon or something.” That’s what really got a lot of attention from a lot of different groups all across the map, and it was really just a real process of being able to having the privilege of working with these athletes, but also speaking to their coaches and speaking to triathlon teams and Special Forces and all these other groups, and learning from them and learning their best practices and coming back to apply it to my practice overall, so it’s really been just this… Way too late for a long story short, but talking to all of these people from all across different walks of life and different backgrounds, and trying to take the best practices from each one and put them into my practice.

Brett McKay: Yes, you’ve broken down that barrier that stands between strength and endurance, ’cause… Look, I came from a strength training background too. That is my main focus. And you always hear, well, you can’t do endurance stuff ’cause your cardio is gonna get in the way of your gangs and your recovering your session, but I think that’s starting to change. A lot of people who are in the strength side of things, they’re starting to see the importance of the cardio element.

Alex Viada: Absolutely, absolutely.

Brett McKay: Okay, so the reason I want to bring you on is, ’cause you’re a big proponent of what’s called Zone 2 cardio. In the past year, I’ve gotten really into this, ’cause like you… I was doing a lot of strength training, heavy pulling, but neglected my cardio, and I just felt crummy and I thought, maybe this is… There’s an element of fitness that I’m lacking, so I’ve gotten really into it.

Alex Viada: Excellent.

Brett McKay: And I want to see you bring your expertise into this. Before we get into the benefits of Zone 2 cardio and how to do it, we should probably start off with what we mean by cardio zones, I think people have probably heard about this. If you go to a treadmill at a global gym, you see the zones that you can get into, so what are cardio zone scientifically?

Alex Viada: So yeah, this is really interesting because I think even just trying to… Try to define them, and you sort of get into some of the question marks that still even exist in the endurance training community, so the entire idea behind these zones and… First of all, what makes it confusing is there’s more than one system of zones, there is a zone system from one through four, they’re ones from one through five, there’s… I’ve seen ones out there from one to seven, but when we typically talk about zone 2, what the heart rate zones or what the training zones roughly correspond to, are various metabolic shifts that happen in the body as you progress from one level of intensity to the next. As you’re training, as you’re running, as you’re cycling, as you’re doing anything else, the body is compensating and basically utilizing the appropriate energy sources and undergoing the appropriate hormonal and neurological response to achieve whatever objective you set for it with regards to actual stress, with regards to actual stimulus. When we talk about Zone 2 cardio, we’re referring to a very specific sort of range of physiological stressors that the body is responding in a certain way, to a certain level of intensity that roughly corresponds to the point just before a few metabolic ships are made before you progress into the higher zone.

So when we talk about zone 2, it’s not really about heart rate, when you look at a lot of cardio machines or you look at a lot of personal training certifications, they say, “Well, Zone 2 is 68% to 75% of your max heart rate.” That’s more correlative. Really Zone 2 is referring to that period of time before your body begins to make that shift past its first ventilatory threshold, which really represents the point at which you start to get accumulation of a lot of metabolites, you get a shift in blood pH, you get a change in the amount of lactate typically found in the bloodstream, so it’s really… If we think about cardiovascular training zones, consider them inflection points where the body is progressing to the next level of energy generation. I think that’s the best way to put it.

Brett McKay: Okay, let’s talk about that kind of a walk-through summary of energy generation, so our body to live and function, it has to use… Has to use energy, and depending on how intense we are doing stuff, it’s gonna use different sources of energy. So let’s just start from the lowest zone one and then kinda work our way up. So when we’re a zone one, we’re just sitting here, maybe taking a slow walk, so what’s our primary energy source?

Alex Viada: Yeah, so the primary energy source in zone one is still… You’re basically looking at fat stores, fatty acids. Now, at all stages of intergenerational, I always think of them as dimmer switches, that it’s not like you only start using your highest intensity energy sources when you’re performing one rep max is like at any point, our body is using pretty much all available energy sources, just to varying degrees. When we’re sitting here predominantly, we are engaged, we’re getting all the energy we need from fat stores, and we have plenty to meet the energetic or the rate of energy consumption. The amount of glucose we’re burning is pretty minimal, and the amount that’s being actually converted and going down the lactic pathway is even smaller. So zone one basically represents the point up to a level of effort where we are burning almost exclusively fatty acids and we are utilizing nearly zero anaerobic processes. No anaerobic fermentation, the lactate system as barely being used, etcetera. So by far and away, we’re talking 95%… I’m sure the number is different, 95% fat burning, nearly zero metabolic stress.

Brett McKay: Gotcha. And then we’re also… The body is using oxygen to create that energy and the energy too, its ATP, is what it’s called.

Alex Viada: Absolutely, yes. So basically, our body is utilizing oxygen, it’s utilizing fatty acids [0:10:09.6] ____. We’re breaking down fat and we’re using that all to… Basically, again oxygen is the terminal acceptor in the electron transport chain. It is a very efficient system. We generate a lot of energy per quantity of fat used, it’s great. Our bodies are very happy here, we can do this indefinitely.

Brett McKay: When we get to Zone 2, so we go from zone 1 to zone 2, and we just upping the amount of oxidation going on?

Alex Viada: We are to a certain extent, now as we continue to increase in zones, what starts to happen is it’s not just that the body is an aggregate doing more work, we’re getting a lot of changes that happen at the local level in muscular tissue, even as every muscle contracts, it briefly contracts, it briefly reduces blood flow to the muscle at the moment of contraction, and then you know when it relaxes, obviously there’s more. But over all the energetic levels begin to rise, and when we’re engaged in zone 2 cardio, so to speak, the oxygen levels or the oxygen requirements suddenly begin to spike, and what’s going to happen is the body actually… You’re gonna notice when you progress from zone 1 to Zone 2, you actually start breathing more heavily, not necessarily faster, but the depth of respiration increases.

The amount of the ratio of shallow breath to deep breaths, ’cause when we’re all sitting here at rest… Most of the time we breathe shallow and every now and then, you take a deeper breath, that ratio begins to change until we’re taking almost exclusively deep breaths, we are still primarily aerobic in terms of energy systems, but there absolutely is on a local level, a certain amount of utilization of anaerobic systems, in other words, a little bit of the fermentation going on to the lactate systems becoming involved, just to sort of generate that little bit of energy. And so zone 2, basically represents that point at which the metabolic demand is rising, but oxygen and fat stores are still… And obviously glucose stores as well, but aerobic systems are still responsible for the vast majority of our energy generation.

Brett McKay: Okay, as we increase the intensity, we shift to zone 3, what’s happening next?

Alex Viada: At Zone 3, what happens is you actually cross a point called the VT1, the Ventilator Threshold 1, and this is actually gonna go a little bit into how we determine these zones. You’ll notice at the VT1, your rate of respiration begins to increase, and one of the things that’s driven by, there are various chemoreceptors and everything else in the body that detect the sudden change in blood pH that’s caused from an aggregate rise in carbon dioxide, that basically means that the CO2 levels in the blood, basically your body, the muscle cells are generating, they’re utilizing energy at a faster rate than your standard… Aerobic systems can supply that, so what starts to happen is your rate of respiration increases, your heart rate begins to increase, but we’re already tapping more into the anaerobic systems, we’re tapping more into those fermentation systems and the body is already at that point in this kind of delicate dance where it’s not really able to sustain this indefinitely.

We’re already… Again, anaerobic systems, when we don’t use oxygen, they’re a little bit less efficient, so the body is on this slow pack at that point towards a loss of ability to meet the energy requirements. So zone 2, you can’t really do it forever, other things will break down, but you can do zone 2 for an exceedingly long period of time because it’s so sustainable. Crossing that ventilatory threshold represents again a slow accumulation of these metabolites and a gradual slow decrease in our body’s ability to sustain a given level of intensity.

Brett McKay: And we’re starting from making that shift from using fatty acids to using more… Starting to use glucose more to get that ATP.

Alex Viada: Exactly, and not just using glucose, but also using glucose in anaerobic metabolism, which is actually less efficient. We generate less ATP or less energy per unit of glucose when we do… When we’re processing it through anaerobic systems than when we do when we’re processing it through the aerobic systems. So it was kind of liking a little bit too afterburners in a jet. Yes, we can produce a lot of energy that way, but we’re using four times as much fuel per unit of energy produced.

Brett McKay: Or another difference between Zone 2 and Zone 1 and then Zone 3. With zone 2, Zone 1, when using fatty acids and oxygen, the mitochondria in your cells are creating the ATP, and I think in glycolysis we’re using glucose to create ATP, that occurs in your cytosol, it doesn’t occur in the mitochondria, is that right?

Alex Viada: Yes, yeah, in a lot of cases, like I say, a lot of the lactate-producing systems can occur in… Exactly, in other systems, so this is no longer strictly a mitochondrial-based process, and in fact, again, the process of conversion of lactate back to glucose or back to glycogen is much more systemic, this is less infinitely sustainable by those organelles. Yes.

Brett McKay: Alright, so in zone 3, you’re starting to use more glucose, what happens in zone 4… Is it just that… You’re just using more and more glucose? When do you start… When do you start using other energy sources?

Alex Viada: So when we actually crossed into zone 4, that’s where it gets a little fuzzier, the line between zone 3 and zone 4 is some people like in the ventilatory threshold too, it’s when we actually start to get such a high utilization of these anaerobic energy systems that you start to really get… I wouldn’t say an uncontrolled, but you get a steady accumulation of metabolites. In other words, the body is not clearing these metabolites, it is not able to sustain this level of intensity without an eventual crash. So we’re using more anaerobic fermentation, we are getting to the point where the body is not able to keep up with a given level of work, and as a result, the… For example, the lactate levels which are used kind of go off into the stratosphere, and this is generally considered a level that the individual will rapidly fatigue at.

In other words, there is a constant accumulating fatigue throughout an interval, whereas Zone 3… Let’s say a gifted marathon runner can run the entire marathon and get equivalent of zone 3. If they cross into zone 4, they’ll probably begin cracking… No, of course, for a marathon run of the difference between Zone 3 and Zone 4 is actually very small, but that’s a different story, but basically at that point, when you cross into what we typically consider zone 4, that’s unsustainable. We are using a lot more of very short-term energy systems, and we’re using heavy amounts of anaerobic glycolysis, which causes rapid fatigue.

Brett McKay: And also when it… Zone 4 and the zone 5, if that exists, there’s debate about that, you start using creatine and recycling ATP, basically, right? So it’s like when your body uses ATP to create energy, it loses a phosphate or something, and then the body is like, Okay, we can use that… Used up, it’s called ADP now, and then we’ll take creatine that’s in the system and we can make ATP really fast. But it’s not very efficient.

Alex Viada: Right, exactly, because what happens at lower intensities, ATP is constantly being generated, we’re generating a huge amount of ATP per mole, or let’s just say per gram of fat, we’re generating a huge amount. And that’s great when we’re at rest because there’s so much fat in our body, relatively speaking, we’ve got the equivalent of tens of thousands of calories of work that our fat can do. When it comes to glucose, when it comes to glycogen, we have much less… Our liver only really has about 400 to 500 calories worth of work it can do, whereas our muscles have several thousand, so even so if we think about it over like let’s say a marathon, we’re probably… If we had to do that on strictly glucose, we would burn through our systems, but we would burn through that very quickly. Of course, if we were to do that even faster and go through a process of fermentation that… Let’s say our muscles are capable of doing 2500 calories worth of work with the glucose that’s in them, that’s through aerobic systems. If we do that through anaerobic systems, we’re really only capable of doing anywhere between 500 and 600 calories worth of work with that same fuel, so not only as we go up in energy systems are we getting… Are we looking at smaller pools of energy, we are also looking at on aggregate the body being able to do less work with the stores we have available.

Brett McKay: Okay, so just to recap here, zone 1, zone 2, you’re primarily using fatty acids, you’re using oxygen mitochondria to create the energy or ATP you need to do whatever, as you shift into zone 3, you start using more glucose, and I think you made the point this isn’t either/or this is sort of like… It’s a dimmer, I like that analogy. And then as you shift into the zone 4, it’s more glucose and maybe even using recycling previously-stored ATP. Do you think there’s a zone 5? What’s your take on that?

Alex Viada: So a lot of that really depends. And you can already tell that since everything is a dimmer switch, we’re talking about pretty fuzzy definitions here, and I think that’s actually where a lot of confusion comes in, and I think something that people probably wanna reiterate is how complicated this actually is, it’s like there’s no definitive switch between zone 2 and zone 3, even though we like to say there is. There’s no definitive switch between zone 3 and zone 4, Some people included zone 5 and say, Well, that represents the pure Alactic systems as they call it, we’re talking about such a high level of intensity that we are just using the ATP CP systems, for example. So that’s just super high intensity sprints of 10 seconds or under. Some people like to differentiate that, I don’t particularly find it very useful, because I think the entire purpose of planning in zones is to look at approximately… Stimulus, how long an athlete can sustain it and what it means metabolically, if you start to get into zone 5, you’re almost looking at something that’s sort of akin to higher reps strength training or explosive training, and it’s not really a useful figure, so I only tell people to really worry about one through four.

Brett McKay: So I think it’s a good background, of science we geeked out there. Let’s start… Let’s dig into this. When most people do cardio, what they think of as cardio, so it’s like a run, or maybe they’re doing a body weight workout, what zone do they typically end up in?

Alex Viada: You know, most people when they’re doing cardio, if they just decide to go out for a run, they are usually sitting right in zone 3, and I think that really is probably at the heart of what a lot of we wanna discuss today is how easy it is or how often people think that they are not getting a cardiovascular workout unless they are exhibiting all of the signs of actually being in that zone 3.

Brett McKay: Yeah, I think a lot of people, when they think workout, you gotta be… You had to… You gotta hurt, bro. It’s gotta be… It’s gotta be a struggle and out of breath and super-winded, like why do you think the zone 2 gets the short thrift… Particularly by weekend warrior type athletes, so I think if you talk to professional athletes, they understand the importance of that sort of zone 2 stuff, what’s going on with just the regular Joe who wants to exercise?

Alex Viada: It’s such a good question too, because I think that… I think a lot of it just comes down to based on what our concept of exercise actually is, and I think one of the reasons why this is tough is if you’re a high level athlete and you’re doing zone 2 work, you’re still running… You’re still running pretty quick… You know, I always talk about the story back when I used to train, I used to run around Duke University. And because they have a sports performance lab there, they would sometimes have a lot of Kenyan runners come down, again, some of the best runners in the world, best the best mid-distance runners that probably have ever lived. And it’s funny ’cause I used to run the trails down there, and these guys would pass me at probably two minutes per mile faster than what my high zone 3, low zone 4 pace, and they would be having relaxed conversations the entire time, and I think for some of us who don’t realize how good elite athletes are, we think, Okay, these guys are going for an easy run, they’re going fast, if I’m not at the very least going for a fast jog, I’m probably not getting anything out of this whatsoever, if I’m not sweating, if I’m not working hard, if I’m not doing any of that, how can this possibly be exercise?

What am I getting out of this? And I think that’s a really… It’s a really dangerous mindset, and honestly, when I first got back into running back in 2007, that’s part of what caused me so much harm to both my lifting and my running is that… That’s a lot of work. And I think for most people, they wanna see, be seen in as doing exercise, they don’t wanna think, well, if I’m going for a fast walk, oh well, that’s not training, anybody can do that. I wanna go out there and work, and not realizing that probably going for a fast walk for them represent zone 2, and that’s probably what they should be doing.

Brett McKay: And also I think that’s something that contribute to that, it’s just like the fitness literature, you pick up Men’s Health, and it talks about HIT workout, so everyone’s gotta be doing HIT workouts.

Alex Viada: Oh man. Yeah, I can’t tell you again, back when I first started… First started doing all this stuff, HIT was everything, and the whole idea was… Hell, I remember working with a lot of strong man athletes and talking to them, ’cause again, again, early on in my career, I was talking to other powerlifters, Well, what do you do for cardio? And strong man, what do you do for cardio? “Well, oh yeah, I push heavy sleds and tire flips, and that’s my cardio right there,” and obviously, we know that’s still good stuff, but to them, that was kind of a minimum for cardio, anything easier than that is just a waste of time.

Brett McKay: Oh, so let’s dig into more about zone 2. So how do we figure out what our zone 2 is, how do we, how do you know… ‘Cause you mentioned… So you said zones are more about the energy sources that we’re using, the metabolites, the changes in hormones that’s happening in our body, so how do we figure out if we’re in zone 2 or not?

Alex Viada: Yeah, absolutely, yeah. ‘Cause there are a lot of systems out there. Some people use heart rate, and while that’s good for some, the problem with using heart rate is first of all, everyone’s max heart rate is different, the whole 220-minus age or any one of those systems are really only good for about the middle, 60% to 70% of the population, and even then there’s kind of a plus or minus eight or seven standard deviation on that, and what I mean by that is, let’s say with 220 minus age, it tells me my maximum heart rate should be 178. Well, that could be plus or minus eight, so my maxi heart rate could be anywhere between 186 and 170. If I’m trying to calculate 70% of that, that’s gonna give me a crazy number, so I tell people, forget about the heart rate zones. Don’t worry about that. Some people say, Well, you should use a lactate meter and check that, that doesn’t work either. The easiest way I tell people is, Look, when we talk about zone 2, we’re talking about a metabolic shift, so let’s find the most obvious metabolic shift that happens with the most profound impact that you can see, and that would be your rate of breathing.

So when I have people do a zone 2 test, which I also call at VT1 test again, talking about the first ventilatory threshold, what I have them do is basically just continue to first start out on a walk and then every minute increase their pace ever so slightly tracking their heart rate and tracking their pace until they get to a point where they can no longer speak a 15 to 20 word sentence without interruption, when they get to that point, it represents that inflection point where the rate of respiration is increasing, which corresponds to a change in blood pH, and the reason that’s so accurate is because that change in blood pH right there, and that change in the need to breathe and respiration rate almost perfectly corresponds to those various metabolic shifts that represent the shift from zone 2 to zone 3. So basically, when you can’t carry on a conversation is legitimately when you’re making pretty much the biggest metabolic shifts out of zone 2, it is the easiest way to determine it, and it’s ironic, it’s actually interestingly one of the most accurate, even in lab setting.

Brett McKay: So the talk test is the talk…

Alex Viada: The talk test, that’s it.

Brett McKay: So yeah, with the heart rate, I’ve seen different stuff, and what’s confusing with the heart rate thing about zone 2, is that you’ll see different percentages, so I’ve seen one… The one that I’ve seen a lot is 70& to 80% of your maximum heart rate as zone 2, then I’ve also seen, well, no, that’s too high. It’s actually 50 to 65. What I’ve done to hone in on my zone 2 intensity is I did the estimate based on your age, and then I use the talk test to refine it, so the estimate basically just kind of gave me a ballpark to being next to… And so I’ll use my Apple watch and I’ll get there, and I think right now it’s like 140 is like for me, is 70%, 80%. And then if I’m… If I could still talk, then I’m in the right spot. That’s how I’ve done it.

Alex Viada: It. Exactly, exactly. Yeah, and that’s it. That is by far the best way to do it. The heart rate will kind of give you that starting ballpark and from there, you very much… It… Again, I think that kinda drives home the point though, it takes a little bit of trial and error, you actually have to go out there and you actually have to read your body a little bit and say, Okay, well, is this working for me? Because again, the other thing is each one of us has a different heart rate reserve in different zones, like difference in heart structure, difference in, there are so many other factors that can be involved in changing where these zones are that I think the way you’re doing it, the way you’re articulating it is perfectly right.

Brett McKay: What’s your thoughts, so one thing that I’ve heard on some lazy researcher that does a lot about zone 2, and he says to get the most benefit from zone 2, you wanna get as close to the upper end of zone 2 and stay there as possible. What’s your thoughts on that?

Yeah, I would say that’s pretty accurate, it’s, again, we’re talking about dimmer switches here, but if you’re… It’s a little bit like saying when you’re weight training, it’s going, Okay, well, what’s the difference between one rep in reserve and two reps in reserve, if we’re looking at, say, an effective reps model, and by that, I mean, obviously, we don’t wanna train a failure, let’s talk about zone 2 is training less than failure, obviously, the closer we get to that threshold, the better, the more work we can do per unit of time without getting into the point of diminishing returns. So going much below that VT1 threshold, I think it’s tempting to sometimes back off a little bit too much as well and go a little bit too easy, so I think the take home here is we wanna make that conscious decision to operate as close to that ventilatory threshold or that zone 2 threshold as possible, otherwise you are… You’re leaving a little bit out there on the table every time, and again, the purpose of zone 2 is not to say go out and be lazy, it’s saying control your throttle, and that means, of course, don’t go too easy either because then you’re probably not getting much of a training stimulus.

Brett McKay: Gotcha.

Alex Viada: So yeah, I would agree with that.

Brett McKay: I wanna throw another shoutout to the Apple Watch, they got a new feature now, when you do your exercises, it’ll actually show you what zone you’re in, I don’t know if you’ve seen this, and it’ll actually have this arrow and it’ll be like you’re at the bottom end of zone 2 and then you’ll start getting closer the… It’ll start shifting, and then it’ll tell you right now you’re zone 3. It’s… Again.

Alex Viada: That’s great.

Brett McKay: It’s not super accurate, but it gives you an idea, it’s nice to have that number there to help you have hone in on it.

Alex Viada: And you know, I just gotta say from a personal level, at first I resisted a lot of wearables and a lot of devices, and now I use them so heavily in my coaching, and I think for a while there, I felt like people are relying on them too much, but what I really like now about a lot of the feedback that they give is they do force a lot of people to be a lot more in tune with what they’re doing. So rather than just going, Okay, I’m just gonna go out for a run and zone out, which can be good for you sometimes, don’t get me wrong, but having that sort of feedback and being able to be a little bit more deliberate in how you construct your training, it’s really caused a lot of people to pay more attention to what they’re doing and I think that’s a great thing.

Brett McKay: We’re gonna take a quick break to hear a few words from our sponsors. And now back to the show. Okay, we’ve talked about what goes on in zone 2, we talked about how to know if you’re in zone 2, let’s start taking benefits of zone 2 as we pivot… Well, what’s the big deal? Why should I do this? So how does zone 2 improve metabolism?

Alex Viada: So I think the benefits of zone 2, you can pretty much almost say they’re synonymous with exercise in general, because it’s just such a great way to get 95% of all the vaunted benefits of any sort of cardiovascular training while minimizing a lot of the downsides. So as far as metabolism goes, we’re looking at a whole range of things, we’re looking at the same improvements in nutrient partitioning and seeing positive effects on insulin sensitivity and glucose disposal, all of these things absolutely play a factor, and though you know as you engage in zone 2, you are actually up regulating a lot of the mitochondrial enzymes, and in fact, your entire mitochondria profile to actually more efficiently burn energy, anaerobically, we’re looking at huge benefits to glucose disposal, we’re looking at huge benefits again to just again, our ability to actually perform more work on an hourly basis than we would have in the past.

So even the quality of our meat is improved because we can be more active because our heart pumps more efficiently, our mitochondria are actually generating more ATP at rest or have the ability to do so, which allows us to be more active in general, with less cost. Metabolically it lets us even get more out of our weight training sessions, we can increase the density of our weight training sessions because we’re recovering faster in between each individual set, which is I think something we don’t take into account. If I’m doing a weight training program at all, if I can take a little bit less rest time in between a sets, I can potentially do more sets, I can potentially do the same amount of work in less time, giving me more time to do other things. Overall, it allows for a higher level of activity at a similar level of aggregate stress, and I can’t think of a single downside to that.

Brett McKay: Yeah, and I think I’ve read research that whenever you do zone 2 at that upper end of zone 2, your body starts, like in a response to that… It’s like a stress, right, and so your body adapts, and so one thing is, so your mitochondria gets more efficient, but then your cells actually start producing more mitochondria, and so you’re able to produce even more energy, which gives you all those benefits you just talked about.

Alex Viada: Exactly, exactly. Like you said, a mitochondrial profiles, which is not just the enzymes in the mitochondria, but it’s the number of mitochondria as well, it’s a profound, profound difference, you’re basically making every single cell a lot more efficient, a lot more capable of generating energy, and honestly, it reduces a whole host of other things. Like for example, there’s less oxidative stress because we’re able to metabolize energy more efficiently in the oxidative system, we’re looking at less metabolite production at any given level of intensity, so we’re looking at the same daily activities causing us less stress, less hormonal stress, less oxidative stress, because we do a lot of zone 2 cardio.

Brett McKay: Let’s talk about zone 2 in cardiovascular health. What’s going on there?

Alex Viada: Sure, so again, it’s got a lot of the same benefits that we typically associate with cardio, bigger stroke volume, better contractile, less ejection fraction, which is the percentage of blood that’s actually pumped out goes up. One of the best things about zone 2 cardio though, is the increase in cardiac preload or what is called eccentric hypertrophy of the heart. So…

One of the most important things when we look at the heart muscle is not when we work the heart, when we train the heart, it’s not just that the heart gets stronger, concentric hypertrophy of the heart is basically strengthening and thickening of the walls of… Especially the left ventricle to allow the heart to pump harder and pump more blood out on every contraction, that’s not the whole picture though, you see the heart actually becomes more efficient when it actually takes more blood in, so when we think about it… After the heart pumps and now it’s re-expanding and relaxing, what zone 2 cardio does by increasing the overall rate of blood circulation is you’re actually increasing the amount of blood flowing into the heart, and zone 2 cardio is right in that sweet spot where that “pre-load” that allows the heart to actually take in the optimal amount of blood, actually causes the heart muscle to stretch a little bit, the more eccentric hypertrophy, which effectively refers to the flexibility of the heart, the more of that we get, the more efficient the heart becomes, and not only does the heart become more efficient, but we also alleviate some of the issues that come from excessive concentric hypertrophy, which can include things like, oh, changes in signal propagation through the heart.

So basically, what I mean is this, if all we do is high intensity work, we are doing a lot of like, let’s say, almost muscle building, body building for the heart, but by doing so much of that without doing enough lower intensity work, we’re not also doing everything we can, for the pre-load, for the elasticity and flexibility of the heart. Doing zone 2 work allows our heart to be more efficiently, it allows us to put more blood per contraction, and it’s also extremely good for the overall, I’ve another way of saying like signal quality within the heart muscle itself. So it’s a little bit like if you go too hard all the time, it’s like trying to do a bike pump too quickly, it’s not efficient, or it’s like trying to pull a rower too quickly, anything where the optimum rate of cycle is not super fast, if the heart is doing nothing but pumping up really hard against contracted muscles, ’cause all you’re doing is sprinting and your muscles are working super hard, you’re not gonna get those same benefits to pre-load and elasticity that you get from the lower intensity work. So for cardiovascular health, it really represents a sort of critical part to the puzzle that you’re actually missing out on if you do nothing but high intensity work.

Brett McKay: Does that increase in volume of blood in the heart, does that trickle down to other parts of the vascular system like arteries, veins, capillaries?

Alex Viada: Yeah, absolutely, yeah, that increase in vascular elasticity is actually a big part of it as well, because that takes place pretty much across the entire system, ’cause arteries are not… Arteries are already fairly strong, they’re muscular vessels, they’re fairly strong, but again, if we are simply contracting the heart really hard against occluded vasculature, like let’s say I’m contracting my quads really hard, ’cause I’m doing a set of squats, or I’m doing a set of sprints, my heart is really pumping hard against that, the arteries are contracting basically to try to force that blood into that working muscle, that’s not always ideal. The elasticity allowing for the constant blood flow and basically allowing the increase in capillary perfusion, increasing the number of capillaries and blood vessels, and actually doing everything you can to reduce that back pressure a little bit actually does improve arterial compliance, or in other words, that is just one other measure of overall heart health and artery and cardiovascular system health, again, potentially reducing the likelihood of a future vascular disease, so it’s extremely important.

Brett McKay: The one thing I’ve noticed too, with the sort of a metric I’ve seen is that my cardiovascular health has been improving since I started zone 2, is my resting heart rate has been going down since I’ve started. That’s good.

Alex Viada: Yeah. Absolutely, yeah, especially because doing a lot of zone 2 work as well, just in terms of even the autonomic nervous system, is nowhere near as stressful because it’s… It actually… It does, obviously, you’re improving your heart health and the amount of blood pumped per contraction, which all lowers your resting heart rate, but also it really helps shift the autonomic nervous system balance a little bit more parasympathetic when you’re at rest, which can also do wonders for your ability to relax, lower your resting heart rate, sleep better. All those other things.

Brett McKay: On a similar note, is there any research about zone 2 helping with mood disorders like depression or anxiety?

Alex Viada: You know, that’s interesting because I think it’s difficult to test and it’s difficult to isolate zone 2 directly from a lot of other cardiovascular activity or a lot of other cardiovascular training, because pretty much all exercise does help with a lot of these things, what is interesting, and I think where we have to start to find correlates is zone two’s effect on things, again, like sleep quality and the lower incidents of the sleep disruptions, ’cause one of the challenges with exercise, particularly to treat anything from mood disorders to depression or anything else, is that exercise has its own set of stressors, and if people are already dealing with some form of depression or mood disorders or sleep disorders or anything else, exercise certainly has a positive effect, but it can also do things like compromise sleep quality, if done at too high intensity, or it can create its own level of stressors, it can create its own high amount of sympathetic drive during the exercise itself. The nice thing about zone 2 cardio is both theoretically and in some of the preliminary research I’ve seen, it does seem to be able to convey a lot of the benefits of exercise on various mood disorders, depression, etcetera, but without a lot of the potential costs to overall individual stress.

So again, it’s sort of that sweet spot where you’re getting the benefits of a lot of this exercise without a lot of potential cost. So in aggregate, it represents a great intervention for anyone, again, dealing with issues like depression or distraction or anything else. There are also a couple of other interesting benefits to doing things like running outside, and I think talking anything from the phenomena of ocular flow to just, again, greater sun exposure and all that, but that’s a different issue.

Brett McKay: Yeah, I’ve noticed that my sleep has gotten better since I started Zone 2, ’cause before, when I was just focusing on strength and power lifting, I would… I’d have my rest day well, you don’t do anything on a rest day. Your muscles gotta recover.

Alex Viada: [chuckle]

Brett McKay: And then since you don’t move your body, your body is like, “Well, you’re not tired.” So you’re gonna have a crappy night’s sleep, but since I incorporated the Zone 2, since it’s a low impact as it doesn’t destroy you, but it still tires you out enough where you can have a good night sleep.

Alex Viada: Yeah, and it’s great ’cause one of the other things is awesome, when we’re talking about things like, oh, sleep cycles and the suprachiasmatic nucleus and melatonin release and all those things that govern things like your circadian rhythms, being able to engage in an activity that is constantly improving your body’s ability to process and dispose of glucose and basically undergo a lot of that. Your process of digestion and metabolic shifts and all of that kind of stuff, it allows the body to go through its normal sleep wake cycles a lot more smoothly and efficiently so you look at a lot of things like decreased sleep latency, the spending less time transitioning between different phases of sleep, all of that is extremely positive, improves your sleep quality, great for sleep architecture, all of those kind of trickle-down effect.

Brett McKay: Another benefit is I’ve gotten trimmer since I started Zone 2, I’m not… I’m not as fat, I’m not as chunky as I used to be. And what’s crazy is, it’s not hard, right? And it’s just, it’s weird, I’ve had to start eating more because to actually gain weight because I’m burning more… I’m probably burning an extra maybe 1500 calories a week by adding in Zone 2.

Alex Viada: Well, yeah, and that’s the other thing that’s great about it too, is the whole concept of caloric flux or metabolic flux, which is the idea that let’s say you just remain ISO-caloric just by lifting and doing as little activity as possible. Now, let’s say I burn 500 calories a day from doing Zone 2 work, but then eat an additional 500 calories a day, all else being equal, the greater the overall caloric or metabolic flux, in other words, the greater the amount that you both burn and take in. The better your body composition is going to be at the the end of any given time than it would be otherwise. So one of the best things you can do overall to look better and feel better, and everything else is move more and eat more to compensate.

Brett McKay: So metabolic flux, eating more and exercising more is a good for body composition and Zone 2 cardio helps with that because it’s a type of exercise that you can do a high volume of and it’s not gonna beat you up.

Alex Viada: Exactly.

Brett McKay: But is it good for weight loss and in any other way? I think a lot of people might have heard of Zone 2 as the fat-burning zone, they’re at the treadmill at their gym, they see, “Oh, you were in the fat-burning zone.” Is that an accurate label and will it help you lose more fat relative to other types of exercise?

Alex Viada: Yeah, so that’s kind of been one of these things that was… I think originally from a metabolic standpoint is maybe not wrong, but it’s really not right either, ’cause really… When you talk about fat-burning zone, you have two questions, you’re saying, “Well, okay, am I burning the most fat possible per minute of activity, and am I burning the biggest proportion of fat compared to other substrates?” Because technically, the highest intensity work you can possibly do, burns more fat per minute than any other level of intensity of exercise. If I go out there and I’m just sprinting along and running at a peak velocity, I’m probably gonna burn more absolute fat overall and use more aerobic systems overall in the course of 10 minutes then I would buy going slower, but the problem is there are so many other limiting factors that overall, if that’s all I do, I’m probably not gonna end up burning that much directly. The biggest fat-burning zone as far as intensity goes, will be, if I’m just sitting here lying flat on my back, for example, the percentage of energy I’m generating via fat oxidation is the highest. So Zone 2 kind of represents an aggregate, it is where the percentage of fat is still notably high and the volume you can do is the highest…

So all else being equal, that’s the point at which over the course of a week, I can burn the most fat while not simultaneously not burning out and not working at too high an intensity, but it’s kind of meaningless because fat burning and body composition change is so much more than just how much fat you’re burning during exercise, so I think in that regard, it’s a bit of a misnomer. And you know what, if you’re trying to do activity to maximize caloric flux and you’re trying to do activity to burn the most while simultaneously taking in significantly more, Zone 2 is probably the only way to really get your caloric flex up high enough, unless you’re the kind of person who can spend eight hours on their feet per day walking around. Zone 2 really does help you maximize your caloric-flux and in that case is one of the best for a body composition, but just as far as actually being in a fat-burning zone, it’s not… Again, what you burn during exercise isn’t necessarily indicative of whole body metabolism or body composition change.

Brett McKay: Well, another thing, correct me if I’m wrong on this. I think a lot of times when people will hear fat-burning zone, they think, “Well, it’s burning the fat on my belly.” And not necessarily… I think our body’s efficient getting to that stored fat, that takes a lot of work, and it’s only gonna go there when it really needs to, so if you’re burning fat in Zone 2, you’re likely just burning the fat you’ve consumed in the past 24 hours.

Alex Viada: Yeah, and that’s really it. I think that’s the shift people need to think about in their mind is your body is going to make use of what energy stores it’s gonna make use of in whatever order it deems most efficient. It’s not gonna say, “Oh, you’re in the fat-burning zone, let’s immediately ignore all this glucose floating around the system and lipids and everything else that’s in the GI tract adjusting right now, let’s go straight to the belly. No, it’s not gonna do that, it’s gonna use the easiest, most accessible stores for energy, and again, and what we’re getting at here is what really taps into that, “Belly fat,” is when your body decides in its own metabolic calculus that it’s time to really tap into those stores from that particular area, which is gonna be so much more function, again, of lifestyle, aggregate caloric intake, a whole host of other things that we could probably spend an hour and a half listing off.

Brett McKay: Yeah, that makes sense. So Zone 2 can help you lose weight, which allows you exercise… Lose body fat because it helps you exercise more. And over the aggregate, if you do that long enough, your body is gonna start dip it into that every now and then to help you shed some of that stuff.

Alex Viada: Exactly, and I think the reason why I think it’s personally great for our body composition changes again, like we’re talking about, it lets you do so much quality work that has a beneficial effect on your metabolism, has a beneficial effect on mitochondrial profiles, insulin resistance, all of that. It lets you do a lot of it and it still leaves you the recovery you need to do a lot of the especially productive, higher intensity work, the lifting, everything else, and again, letting you really keep that caloric flux relatively high with very low recovery cost.

Brett McKay: So I think we made a good case that Zone 2, it’s great for cardio health. It’s great for your metabolism. It can help with things like type 2 diabetes. It can help with sleep. Let’s talk about for people who are… They’re an athlete, they have a sport, they’re trying to focus on, what’s the benefit of zone to cardio for endurance athletes, ’cause this seems counter-intuitive for a guy who likes to do 5Ks or whatever, why would I go really slow if I need to… Usually you think, “Well, I need to train fast to go fast.” But what you’re saying is actually, no, you spend most of your time going slow, how does going slow help us go fast in a meet?

Alex Viada: Well, I think what’s really interesting is, if we’re familiar with polarized training is the whole idea that you do 80% of your work at zone two and 20% at Zone 4. So in other words, in your training you’re doing most of it easy and some of it hard. Interestingly enough, a lot of that was arrived at just by observing elite athletes, not by saying, “Okay, we’re gonna try this.” But by saying, “Okay, let’s see what the elite athletes are doing.” And interestingly enough, if you look at the true elites, in many cases, they’re doing 85% of their work in their Zone 2 or up to 88% of it in their Zone 2, but I think what’s really interesting is, of course, if you look at their high intensity work, it’s the total number of high intensity minutes they’re doing per week, not the number of high-intensity workouts. So just to break that down a little bit. I think when a lot of people think about doing like say an interval workout, they say, “Okay, I’ve got a 45-minute interval workout coming up, at 45 minutes of hard intervals.” In that workout, they’re probably only spending about 10 to 15 minutes actually doing hard work, the rest is rest periods.

When you’re putting together a polarized program, all of that high intensity work, you only count the minutes you’re doing high intensity, so I think that’s one thing I wanna make sure people know is that when we talk about doing most of it easy, remember that that’s still a lot of hard work. So when people think, “Okay, well, I don’t wanna go easy, if I wanna go fast.” It’s remembering that since the hard work you’re doing is so tough, there’s no way you can do enough of that to get in the overall quantity and quality of work you wanna do. It’s a little bit like saying, Okay, so to be a good runner, to be a fast runner, I’ve got to obviously improve running efficiency and leg turnover speed, and all these various components of metabolism and all of that. But realizing that Zone 2 allows you to do a tremendous amount of work to, again, improve the number of mitochondria that you have, to improve the amount of fat and glucose you can burn, aerobically, all of those things are basically increasing the size of your engine and letting you do more of the high-intensity work, which is going to translate to being able to actually do an aggregate a whole lot more training, a whole lot more quality training, and spend a lot more time developing all those factors in performance that just take a lot of time and volume to develop.

It takes a long time to develop the mitochondria to be a good runner, it takes a long time to build up your heart strength to be a good runner. If you’re just doing Zone 3 and Zone 4, you’re probably burning yourself out before you can do enough work for those slow-adapting energy systems. You’re being held back by overall stress, you’re being held back by sheer exhaustion and muscle soreness and all of those things, and eventually you burn out, you start to get sleep disruption, all those other things long before you’re actually dosing your heart and mitochondria with the optimal stimulus to be the best they can be.

Brett McKay: Yeah, that’s a good point. The more you do Zone 2, you’re gonna get more fit, you’ll be able to move faster, but still stay in Zone 2. So it’s like, That’s what I’ve noticed…

Alex Viada: Right. Exactly.

Brett McKay: I’ve had to… As I’ve done more, as I’ve done Zone 2 for a longer, I noticed I’ve had to go faster to actually get into my Zone 2 rate.

Alex Viada: Yeah, exactly.

Brett McKay: And that’s why you watch these Kenyan guys, they’re like in Zone 2, but it looks like they’re sprinting to you, but their body’s like, no, this is actually Zone 2.

Alex Viada: Yeah, it’s crazy ’cause I watch guys like… Are you familiar with Aleksandr Sorokin, the ultra runner?

Brett McKay: Yeah, yeah.

Alex Viada: Yeah, look at the pace he went for a 100 miles. Look at the pace he can do for 24 hours. [chuckle] For him, that’s an easy Zone 2, for some of us for I think for a lot of people listening, it’s like, “Well, that would be a really fast mile pace.” So it really does, as we get that incredibly efficient, we start to get better and better. And again, it increases the density of work we can do as well, ’cause we’re recovering faster between intervals, so not only are we getting faster at our Zone 2, when we decide to then do other work, we can do more of it and recover faster, which makes it a more efficient workout.

Brett McKay: But it’s gonna take a while to get there, it’s like lifting weight, you’re not gonna deadlift 600 pounds in a month. To get to that speedy Zone 2. It’s gonna take maybe years to get there.

Alex Viada: Yeah, yeah, yeah, it does. And I think the thing that is, people sometimes get impatient with it and they think, “Okay, well, this isn’t getting all that much better.” But it does, it takes time, and as long as it’s providing a stimulus, it’s doing what you need. Sometimes things just take time and it’s not as gratifying as HIT where you can just push yourself harder, and every week you push you yourself a little bit harder. It is so much easier in some ways with HIT workout, to just push yourself harder with every week, but not actually be adapting more, you’re just adapting yourself to an uncomfortable stimulus, so you’re getting better at pushing yourself hard, you’re not necessarily improving in your fitness, which is why some people will see themselves hit a wall after six to eight weeks of high-intensity training. It’s ’cause they haven’t really been physiologically improving, they’ve just been improving in their pain tolerance, they’ve been improving in their familiarity with the movements, so they get better, but they really haven’t gotten better as much as they think. They’ve just gotten better at the task itself, they’re not necessarily much fitter.

Brett McKay: Okay, so if you’re a endurance athlete and you’re gonna start Zone 2, you gotta be patient. It’s gonna seem like you’re not doing anything, it literally… If you’re just like just doing the couch to marathon thing, you might just be walking like a fast walk, and that’s gonna be Zone 2, and that… It’s gonna be like that for a while, but over time, you’ll be able to speed up while still maintaining that Zone 2 range.

Alex Viada: Yeah, absolutely, absolutely.

Brett McKay: Okay, so we talked endurance athletes, what about strength athletes? We mentioned some of the benefits kind of in passing. Let’s focus more on that. So you came from the strength world, you’re a power lifter, you’re a big strong guy, and you dead lift like 700 pounds, I believe…

Alex Viada: Yeah…

Brett McKay: 700 pounds.

Alex Viada: Actually set a PR this year, so I’m pretty happy about that…

Brett McKay: What was it?

Alex Viada: 747.5, and I say that because 2.5 fell off the outside…

Brett McKay: No, that’s dang strong. That’s a great pull. Congratulations.

Alex Viada: Thank you very much. I appreciate it.

Brett McKay: So how does Zone 2 help guys who’d like to pull 747 pounds?

Alex Viada: So here’s the best thing, and this is actually the story I always tell because this was actually a client of mine, he was a power lifter, a competitive power lifter, Australian, very, very strong guy as well. We’re talking about a dude who was pulling close to 800 pounds. He’s obviously stronger than I am. It was really funny ’cause I had him doing a lot Zone 2 work, and it wasn’t until about six months in ’cause he resisted the process a little bit, but he was a good sport, he always did it, he started taking his bike to and from the gym, just easy cruising and all that, and it was really funny ’cause after six months, he sent me… He sent me a note and he said, you know, I never really thought about some of the benefits this was having besides heart health and everything else, but I noticed when I was going through my squat worked out now, I was able to put my knee wraps on for the third set, without needing to stop for air and without feeling tired, and I thought that was probably one of the most impactful, relevant things I’ve ever heard a power lifter say, ’cause what zone 2 work was allowing him to do was get through his training session and get through all the work he had prescribed with less overall fatigue.

Which you take any two power lifters or any two strength athletes, and tell one of them, Look, I can get you to competition day having done a 15% more work than everyone else around you, at little cost to yourself, what would you say? And most of them, if they know what they’re doing, would say, “Yeah, absolutely. Yeah, I’d love to be able to do more work, I’d love to be able to program in a little more sport work and a little more high intensity, true power production work without fatigue-ing.” That is one of the biggest, most profound benefits, again, besides benefits to health and everything else is… We’re saying that recovery in between every set, your ability to focus and brace yourself for the next set and mentally get yourself keyed up and potentially do more work in the same period of time, or to continue doing work without actually letting yourself cool down in between, which can be a real problem for some lifters, you’re telling ’em all you need to do is this 20 to 30 minutes of zone 2 a couple of times a week, it’s not gonna interfere with your training ’cause it’s so low intensity, we’re not telling you to go out and do tire flips, I’m telling you to get on the elliptical or the bike for 30 minutes, that’s easy, and you tell ’em, This is gonna make it so you recover faster in between every single set, and when you do your next set, you’re gonna be better recovered.

Feel fresher and have more energy, so you’re gonna get more out of it, that is an undeniable advantage of this type of work for any strength athlete.

Brett McKay: Yeah, so instead of taking an hour and a half to two hours for a training session, could be an hour… Maybe 45 minutes.

Alex Viada: Yeah, yeah, and even then saying like, hey, you know what, one of the biggest problems I think, especially I used to see this with a lot of older school lifters is say Look, if someone’s gotta take eight to nine minutes in between sets of squats, it is really, really… Between very heavy sets, it’s really tough to stay engaged, your muscles are already cooling down. Your cardiovascular system is working so hard to get all those energy stores back that that is not the most efficient or effective way to do it. You wanna be relatively fresh, you wanna be able to just go in and bang out that next set with less rest. And you say, “Okay look, we’re gonna reduce that to three or four minutes.” You’re gonna get four quality work sets worth of work done. And that’s gonna give you time to do it a little bit more accessory work, you might be able to do a little bit more foam work, it might even free more time to do some of that mobility work that you’ve been putting off, that you skip every single session, so there you go.

Brett McKay: Yeah, I’ve noticed that since I started Zone 2, I don’t have the rest as much between sets anymore, which is great, it used to be like five minutes between a heavy… I can do three minutes now, which is… It adds up.

Alex Viada: It really does. It really does, especially when you’re talking about a lot of athletes, a lot of strength athletes when they’re training, it’s like, “Hey, you’re not eating, you’re not resting, you’re not doing anything else in that time.” You’re literally… This is just creating new minutes in your day for you, which I mean, that’s great, and yes, of course, there’s the cost of actually getting on the bike, but we’re talking about quality work time.

Brett McKay: Okay, so if you’re into strength training, Zone 2 cardio can give you better quality workouts in a shorter amount of time, so then you can do other stuff like accessory work, if you’re more competitive or that’s just something you wanna do, or it can just be just a way to get some time back for whatever… That’s what I like about it. My workouts are shorter now.

Alex Viada: Yeah.

Brett McKay: I mean, as you say, you have to add the time in for doing Zone 2 cardio into your schedule, but it’s nice not to have your weight lifting workouts, you have to stretch on and on.

Alex Viada: Right.

Brett McKay: Another benefit I found in my strength training from starting zone 2, and I don’t know, this is just completely anecdotal, this is in one scientific experiment on bread, but it’s helped with some injuries I’ve had, especially tendon injuries, it’s just nice to get it there and get some blood flowing, ’cause the tendons are… They’re not a vascular tissue, there’s not a lot of blood going to there, so the more you can get there to it, it helps that recovery process.

Alex Viada: Yeah, and actually any modality you do, there’s of course, bone remodeling, and tendon remodeling and all of that kind of stuff is a slow process, and of course, even non-impact zone 2, represent some sort of additional stressor on the bones and tendons and everything else that strengthens them over time, potentially in ways that strength training doesn’t, so… Yeah, overall, you’re gonna be more robust.

Brett McKay: So we talk about the benefits and say someone’s listening to this, they’re like, “I wanna do this. How much Zone 2 cardio do we need to get the maximum benefits of it?” Like, what’s the minimum effective dose?

Alex Viada: And I tell people anything more than 30 minutes a week, they’re gonna see some. I tell most people, “Look, hey, if you can start out at 80 minutes a week, you’re in good shape.” Now the recommendations go all the way up to 180, which sounds like a lot, but if you break that into 45-minute sessions, it’s not that crazy. But I basically tell people, “Look, if you can do three, 25 to 30-minute sessions per week to start, you’re already getting a lot of the benefits out of that.”

Brett McKay: Gotcha.

Alex Viada: That is talking about minimum effective dose, if you can’t make time to do that, I don’t know what to tell you. But that is literally all you need to start.

Brett McKay: Any advice for strength athletes, ’cause I think they might be… ’cause they’re so indoctrinated to think, “Well, cardio is gonna get in the way of recovery and gains”, how do you like to incorporate zone 2 into your strength athletes programming?

Alex Viada: I literally tell them, “Look, do it, do this at the end of one of your sessions, if you wanna pound a protein shake or anything else beforehand, go for it.” But the thing I’ll typically tell them is, “Make sure you use a modality that you’re comfortable with. Don’t think you have to run, don’t think you have to bike, don’t think you have to do anything. Find some modality that you feel like you can do comfortably, it can even be the elliptical.” In fact, I’m a pretty big fan of that piece of equipment, because it’s so low impact, you are not fatigue-ing any muscle that you’re otherwise using. You’re not gonna interfere with anything because it’s so different. You wanna do something that, at the end of a session, you feel like, “Okay, this isn’t really a stressor.” So, I tell them, “Look, hop on the bike, hop on elliptical, do the stepper, do whatever you want and don’t hesitate to mix it up, because the modality matters much less than what your heart rate is doing each time, or what your heart is doing each time and what your muscles are demanding. So, don’t be wed to the idea that you have to do this or you have to run and you have to do anything. It’s all good.”

Brett McKay: Yeah, for me, the way I’ve done it is, I train Monday, Tuesday strength training. Wednesday, it’s off day, so I do an hour of zone 2 then. And then, Thursday, Friday strength training. And then I got… On one of those days I’ll do HIT. Like, I’ll do this, bike, just all out or some sort of body circuit. Then Saturday, Sunday, it’s an hour of zone 2 on each of those days. I get three hours, or try to get three hours.

Alex Viada: That’s perfect.

Brett McKay: Yeah.

Alex Viada: Yeah. That’s honestly, for a lot of people, that’s the ideal structure right there. I mean, again, some people, “love a day off’ I personally don’t, I like to do something every day. But yeah, the way you’ve gotta laid out, and that’s the nice thing about it is, since its really so easy to recover from, it’s not like your Monday workout is gonna be tough, because you did an hour of easy work on Sunday, I mean, humans are meant to be able to do an hour of easy work on a given day, and not pay for it, so yeah, it’s actually a good thing.

Brett McKay: And yeah, but if you can’t get an hour, that’s okay. You shoot for 25-30 minutes, three times a week, maybe.

Alex Viada: Absolutely, absolutely. I always tell people that, “Some is better than none.” If you’ve got an aspiring power lifter who says, “Look, I can give you two, 20-minute sessions per week. Is that even enough?” The answer is yes, absolutely it is, you’re gonna see a difference.

Brett McKay: I think the hardest part for me, starting zone two is… I wanted to shoot for an hour, I’ve read that like… I wanna get that… The maximum benefits, I like to maximize things, but it’s just boring. I mean so, you gotta find something to do. So, what I’ve done is I watched Cobra Kai, I got the Cobra Kai on Netflix and now I’m re-watching 30 Rock, while I do my zone 2 and it’s been great.

Alex Viada: Honestly, that’s perfect. Because, when I do zone 2, I will sometimes play video games, I sometimes do my Instagram Q&As when I’m sitting on the bike, just because it forces me to stay the talk test. Yeah, doing something that kind of gets you a little bit out of your head and it makes it a little bit less painful… I mean like psychologically painful for some people. And that’s all good, and that’s actually one of the things I look forward to is… I also say, “Look, this 60 minutes that I’m doing this, this is me time, I can do whatever the heck else I want during this time, I don’t have to do anything, ’cause I’m doing… I’m training, I’m doing something that’s good for my heart, whatever else I wanna do at this time, that’s great. This can even just be my 60 minutes, it’s a quiet meditation time, it’s perfect.

Brett McKay: Or you can listen to the Art of the Manliness podcast.

Alex Viada: Absolutely.

Brett McKay: Yeah. There you go.

Alex Viada: Highly recommended. [chuckle]

Brett McKay: Yeah, I mean like you, I really look forward to Zone Two cardio now, ’cause I just like how I feel afterwards, you get that sweat going, it just feels really good. It’s the only time I get myself to watch TV, so yeah, I really enjoy it. So you mentioned modalities, it’s basically anything to get your heart going, but are there any ones that you like a lot?

Alex Viada: So for me, I actually… I still have my triathlon bike hooked up on a trainer. The reason why I love the bike for me is, I’ve been cycling long enough that I’m a pretty good cyclist, and for me that’s an easy way to get my… To get into zone 2 and on the stationary bike, I can do plenty of other things. That’s always been one of my favorites. I love air bikes and airdynes just because you don’t have to push particularly hard to get into zone 2, because there’s so many different muscle groups working at once. And honestly, one of my biggest recommendations is the elliptical, which I think gets unfairly maligned by a lot of people, but it is a… Provided, you find an elliptical that fits your body size, because they have a lot of different sizes and shapes, and they’re not great for everybody, it’s a great piece of equipment.

Brett McKay: Yeah, I use the ellipticals when I like… We also have an incline treadmill, so I just crank that up as high as you can, and then I go into like… I think the speed is like 3.5, and that will get me at zone 2. The one thing that I had trouble with when I first started experimenting with zone 2 is, I tried to go just running outside. I noticed I would immediately get into zone 3, without even go on that fast, and I would be like, “Oh, I have to walk.” And then, it was just off and on. So, based on my experience, I wouldn’t recommend outdoor running ’cause it’s just so easy to move into the zone three. What are your thoughts about that?

Alex Viada: Honestly, I totally agree. I do a lot of AT-1 tests for new clients, and most of them, I’ll set the treadmill to 4%, and they will be hitting that zone 2 long before they get to a run, and that’s totally, totally normal. It takes quite a few years actually to be an efficient enough runner, unless you’re very light, it takes a lot of years to be efficient enough that you can comfortably run, as opposed to even just kind of shuffle jogging at zone 2. So yeah, that’s very normal. And that’s why… Same thing, honestly, if people are saying, “Look, I would love to be able to just go out and go for a run, or go run some trails or something, if it gets me out of zone 2… ” Okay, if you love it, you can still do it, but that’s not zone 2, I would recommend something else.

Brett McKay: And also, if you’re a strength athlete, that’s a stressor, because you do your pounding against the ground and that might…

Alex Viada: Absolutely.

Brett McKay: One recommendation I have, this came from my wife with her experiment with zone 2 cardio, with running is, if you’re just starting out with running and you wanna do that zone 2, like, do it on a treadmill. And she found that useful ’cause you can set the treadmill flat, you can keep it at a slow, constant speed, and she said, “Even then, you’ll have to stop and walk, ’cause you know, pretty… You’ll quickly go into zone 3 and you’ll have to walk. But she found that just by doing that, steadily, that’s the treadmill run, she was able to get to a zone 2 run outside eventually.

Alex Viada: Yeah, yeah, exactly, because one of the biggest challenges, of course, is with zone two, being able to work up that threshold, that VT1 threshold… If all you do is run outside and push yourself too hard every single time, you are really gonna burn yourself out, probably at a faster rate than you’re gonna make all the progress you want, you’ll see great progress for eight weeks, 12 weeks, but you may end up hitting a wall and you may end up really struggling. You may be struggling to get into the volume that you know you need, you may be struggling to have energy for your lifting sessions and everything else, so that’s when it really becomes critical to say, “Oh wait, maybe I should have slowed down here quite a bit.” And the treadmill is great, contrary to some… To the believe in some circles, the mechanics are not appreciably different than running outside. Basically, if you look at it from a biomechanics standpoint, there are very, very minor differences, and overall, like you’re saying, it really lets you control that throttle and it takes some of the self-imposed pressure. When people are outside, it’s very often difficult to realize how slow a 12, 30-minute, mile jog may be…

Or keep yourself doing that, walk, run and not over-cook it. It’s difficult. You said like, hills, up and down, and also people just don’t like going out and moving slowly. They’re thinking, “Okay, either I’m gonna walk or I’m gonna run fast, I’m not gonna do this sort of walk, jog, slow moving, looking at my watch to make sure I’m not going too fast.” Again, as throttle control, it is such a great tool to use and… Yeah, absolutely, if people really are serious about this and they wanna say, “Okay, well, I wanna do this right.” Yeah, the treadmill might not be the most exciting option, but especially now, it’s probably… Depending on the time of year, it could be even preferable to going outside and it’s worth getting used to it because it also very much teaches pacing, which is something I think a lot of people have trouble with, so it gets that in your head, it lets you control your pace, control your output, provides some valuable lessons and it can, in some ways, help you make more sustainable progress. So, that’s a great tool.

Brett McKay: And then another thing she noticed with her running in zone 1 cardio is that she even got the benefit to her running by doing zone 2 and other modalities. Like, if she just did a walk on an inclined treadmill for her zone 2, she saw that transfer over to her race times, they would dramatically drop and she got a lot faster.

Alex Viada: Yeah, yeah, and it’s great. Yeah, ’cause I think the other thing is with zone two again, it’s… There’s much more transfer between modalities than a lot of the higher intensity work. So, yeah, again, walking, hiking, rocking, cycling, even elliptical, all those things, do have pretty good carryover and represent a good way to vary the direct, I guess, cost and stressors while maintaining most of the stimulus.

Brett McKay: So, we’ve talked a lot about zone 2, what about… Is there a place for zone 3 in your training at all, if you’re like an endurance athlete or just a weekend warrior type guy?

Alex Viada: Yeah. So, there are actually a lot of very good training programs that are called kind of sweet spot training, where you spend a good 30 or more percent of your time in zone 3, which is a little bit more usual. Like, it’s a valid form of training. I think the important thing to remember though, is that, if you are also a strength athlete, first of all, zone 3 work, it’s neither the most efficient way to develop a lot of those like speed systems or higher intensity energy systems, nor the lower intensity energy systems that zone 2 does, just because you can’t do nearly as much of it. If you are aiming to train for a 5K or a 10K or aiming for a triathlon, it’s worth spending some time in that zone 3 doing things like tempo runs, tempo rides, etcetera. Interestingly enough though, when you look at polarized programs, which is again, just zone 2, and then high intensity and sweet spot programs which are zone 2, zone 3 and high intensity, the outcomes are almost the same, but what shifts things in favor of zone 2 is a lower likelihood of injury and a lower likelihood of burnout or over-training.

So, you certainly can do it, and I think, if you are a newer runner and you’re looking to do something like, you wanna get a good 5K time or something else, it’s probably worth spending some time there just to get used to what it’s like pushing yourself for a 20-minute period at that zone 3. As it stands though, it’s a little bit like saying, “Okay, I’m a strength athlete, and I wanna do heavy singles, doubles and triples… ” You know, that has it’s role, and hypertrophy work has it’s role, “But what about doing sets of six with three reps in reserve?” You’re going, “Well, it has a training effect to it, it’s just not really optimal for anything. You can do it, but it’s not the best answer to any training question you could ask.” That’s the way I look at it.

Brett McKay: What about Zone 4/ 5 training, what’s your take on that?

Alex Viada: Yeah, honestly, if you are just a strength athlete and you’re just doing this for health, I would argue you don’t have to do that kind of work. As long as you’re doing some kind of basic strength training or anything else, or even like calisthenics, body weight training, anything else, I would argue, you don’t need to do that if your only concern is health. If your concern is performance, you do need to spend some time… Anywhere between 12% and 20% of your time in those higher range systems, because those do improve a lot of those actually shorter term energy systems and things like intramuscular coordination, and all parts of those things that truly potentiate that base you’re building. So if you don’t do those, you’re gonna be holding yourself back, but again, the nice thing about all of this is, is it really only takes a dedicated period of six to eight weeks to absolutely max out your higher… Your higher intensity adaptations. In other words, if you’ve been doing nothing but zone 2, and you go, ” Huh, I wonder how much fitness I’ve built. Let me start doing some high-intensity stuff.” If you do a good amount of solid high intensity work for six to eight weeks, you’ll see your potential.

Brett McKay: No, I think if you played football in high school, you saw how quickly you can get, “in shape” ’cause you’re just doing wind sprints all summer and then… Yeah, you’re in shape, and then you can see how quickly it goes away, if you just stop it. It goes away really fast.

Alex Viada: Yeah, [chuckle] yup, exactly.

Brett McKay: So yeah, for me, for zone 4, I’ll do two sessions a week and they’re short, it’s like, no more than six minutes where I’m kinda doing maybe an airdyne circuit, 60 seconds on really hard, 20 seconds rest, like four or five times. That’s it.

Alex Viada: Yeah, yeah, I tell people, That’s fine for… 99% of us are gonna realize most of the benefits from it, from that, so yeah, that’s the way I go with it.

Brett McKay: Well, Alex, this has been a great conversation, where can people go and learn more about your work?

Alex Viada: Yeah, so best place is I’m on Instagram at alex.viada, or they can look up our complete human performance Instagram, which has got links to all our sites, educational materials, coaching, you can find my book, The Hybrid Athlete there, which… Oh my God, it’s, at this point, it’s getting on close to eight years old, I think. I’m thinking about writing a new version of it, now that hybrid training’s gotten so big, but I would be… Again, old book, still has a lot of info on it, so yeah, that would be the places to check me out.

Brett McKay: Awesome, well, Alex Viada, thanks for time. It’s been a pleasure.

Alex Viada: Brett, thank you so much. The pleasure was all mine.

Brett McKay: My guest today was Alex Viada, he’s the founder of complete human performance, and you find more information about his work at his website, Also check out our show notes at, where you’ll find links, including a link to an in-depth article that we wrote about zone 2 cardio, the science behind it, the benefits and how to do it. Check that out,

Well, that wraps up another edition of The AOM podcast, make sure to check out our website, at, where you can find our podcast archives, as well as thousands of articles written over the years about pretty much anything you think of. And if you’d like to enjoy ad free episodes of the AOM podcast, you can do so on Stitcher Premium. Head over to, sign up, use the code “manly” as you check out for a free month trial. Once you’re signed up, download the Stitcher App on Android or iOS, and you can start enjoying ad free episodes of the AOM podcast. And if you haven’t done so already, I’d appreciate if you take one minute to give us a review on Apple podcast or Spotify, helps out a lot. And if you’ve done that already, thank you, please consider sharing the show with a friend or family member, who you think would get something out of it. As always, thank you for the continued support, until next time, it’s Brett McKay, reminding you to not only listen to the AOM podcast, but put what you’ve heard into action.


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