Mastering Interval Training for Ultrarunners with Michael Rosenblat, PhD #198

Trail and Ultra Runners. What is going on? What's happening? Welcome to another episode of the Coupecast. As always, I am your humble host, Coach Jason Coupe, and we are back in action after a little bit of a content delay due to all my equipment being lost on my return from UTMB. Every last single stitch of podcast equipment that I actually owned, minus a couple of cables and kind of like miscellaneous things, takes a little bit of time to reassemble all of that equipment, as well as time to reschedule the guests that I had previously scheduled for this podcast. So I'm much appreciative to both the audience as well as the guests that I had scheduled for putting up with a little bit of the delay. But we are moving forward, as all good endurance athletes should do.

The brand new episode of the podcast today and is all about interval structure and how we can optimize our interval structure in order to produce certain physiological adaptations as well as end performance. You longtime listeners of the podcast will know and recognize that this is an area that I focus on very much within our coaching practice, because I feel it is one that can impact you a tremendous amount. Do we want to do shorter 30 second intervals or one minute intervals, or should we favor longer intervals in order to optimize performance, or do we even need intervals in the first place? Can we just simply add volume? So, to get to the heart of all of those answers, I have on the podcast today Michael Rosenblat, who is a researcher that just happens to focus on this particular aspect, and he has produced three separate meta analysis, or meta analysis over the course of the past few years that try to get to the heart of what types of interval structures are going to be better or worse for certain adaptations, as well as end performance. In the course of this conversation, we try to alchemize all three of those meta analyses as well as come up with practical recommendations for you, the athletes and coaches out there that are listening.

I hope y'all enjoy this conversation just as much as I do and are able to take something immediately away from this conversation and apply it to your training tomorrow, the week after that, the week after that and the week after that, throughout the entirety of your athletic journey. So, with that as a backdrop, I am getting right out of the way. Here is my conversation with Michael Rosenblat, all about interval design and how we can apply it to training. Well, like I said, I always like talking to people that are in academia, that also have some applied piece of it, whether they're a practitioner in the space or they interface with other coaches or whatever, because, as you're aware of right, being a coach in addition to being on the academic side, it's always different when you start working with people, as opposed to numbers and research articles and things like that.

Yeah, that's for sure. In fact, it's because of my coaching practice and I'm a physiotherapist as well why I actually decided to go to do research to help with more knowledge, translation and implementation of research to be more applied.

Well, if we could start out with that, because your background is actually really interesting and it's something that I didn't have I didn't actually have a whole lot of knowledge of before I started digging into all these papers so that the audience can get to know you a little bit better. Why don't you just go over what that background is? Because to me, as a coach in the space and a long time coach in the space is actually quite fascinating. I think the audience will find it fascinating as well.

Yeah, actually it has a lot to do with my coaching and so I started off coaching triathlon. I think it was 2004 and I guess I would have been 21 years old and no real education but a personal training background

. As I started getting more and more into coaching and started working with different level coaches, I started having more and more questions about why should we be doing one thing versus another? The answer I got the most, which is the answer I hated the most, was well, this is what's been done in the past, or this is what we think should be done. Of course, the other coaches were probably in their early mid 40s or something at the time and I was 21 and didn't like that answer.

I actually went and did a degree in kinesiology at the University of Guelph. I back to apply to science kinesiology and really got into the health and performance side of things. I knew I wanted to continue into sport from there and that's what ended up leading me to my next degree. I like rehabilitation, which led me to do my master's in science and physiotherapy. Being a coach is very hard financially. It's a hard thing to do to maintain clients and that type of stuff. I knew that I'd want to be able to do a little bit of two things be able to make sure I have a steady job and then also do some things that I love. That's what led me into doing physiotherapy.

I kept coaching along the way. I was reading the literature throughout. It's funny I came across a work from Steven Seiler in some of his earlier work and that's kind of what started to guide some of my coaching practice. I started becoming very successful. I had athlete qualify for Ironman World Championship at 22 years of age. That sounds like in Canada that's a big deal because there's only one qualified race here, there's only Ironman Canada. At least at the time it was as competitive as you could possibly get. I just got more and more interested in literature and I was trying to program my athletes through the literature and that's how my academia through kinesiology and physiotherapy helped. I coached with Triathlon, ontario provincial level coaching, and I coached for the Ontario Summer Games in 2010, right before physiotherapy.

I continued being interested in that and even through my physiotherapy practice, I think about maybe about seven, eight years into practice is when I returned to do my PhD at the University of Toronto. I did a PhD in exercise science with a cardiovascular exercise physiologist, scott Thomas. From there, I think, my interest were to get more into academia and leave clinical practice. I actually kept both. I was continuing to practice and went into academia from there. I actually have something interesting to say about my PhD, though. It was around when COVID happened. I was doing primary data collection and I was looking at things like lab work, doing auction up, kinetics, looking at that type of stuff for interval training and programming interval training. Then COVID happened and I had to basically kibosh my projects and shift more into knowledge translation. That's where I started writing meta-analysis and shifted my work into more biostatistics and looking at all of the evidence on interval training and programming exercise for endurance performance. There's a lot of different things there, but I've done a lot in the last, I guess, maybe 10, 15 years.

COVID has made a lot of people's research pivot, people who are at different stages of their research, and you are obviously right in the thick of the early part of it trying to get it done. That's been a common theme, really. That's been persistent since all the interviews that I've done. Needless to say, you have an eclectic coaching background and almost one that if?

I were to kind of like robotically build the perfect coach. You've got almost all of those elements, especially coming in from physiotherapy, which is something that all coaches are trying to figure out in terms of how to keep their athletes healthy when their athletes get injured and how to get them kind of like back into the field, and things like that. It's something that I personally have greatly appreciated after getting to know you and your background a little bit better.

Yeah, I'd say I think and hope that makes me not just a better coach but also better physiotherapist. Being a recreational athlete, being an exercise physiologist, being a physiotherapist and a coach and having a better understanding of what all the different professions do and knowing what my athletes might need, I certainly would say it's helped quite a bit.

So we're going to talk a little bit about the meta-analyses that you have produced and the theme that surrounds all of them is interval design. And how does that interval design impact different pieces of an athlete's physiology and then end performance? Obviously, I'll leave a link in the show notes to each one of these meta-analyses and any of the kind of supporting literature that we start to talk about, so people can kind of go out and check it and check it out on their own. But one of the pervasive themes within this sphere of research that you always see is they are typically but not exclusively typically done on cyclists. We have a predominantly ultra-running crowd running an ultra-running crowd of athletes and coaches.

Before we dive into it too much, I want to kind of go over that caveat and then why that is important from you, the researcher you just mentioned, you're collecting a lot of your data before you started doing the meta-analyses why that is important from a research perspective. And then the second prong of that is are there any caveats to take away from that into the running world? Do we need to look at cycling research and specifically cycling research on interval design and kind of the impact that it has on physiology and performance. Do we need to look at that through a little bit of a different lens, since the coaches that are listening to this and the athletes are listening to this might be applying it to, or probably are applying it to, a different sport group?

Yeah, and I think that's it's a. It's a great question to think about

. You know the mode of exercise that the research is done in, and it's funny because I never initially thought that interval training research was was done in cycling to the degree that it is. I always just thought it's depending on the mode of sport and that's how I initially approached it. And then, of course, then when I got into doing my PhD and it's why did I design my studies with cycling as opposed to riding or rowing or whatnot? And there's a few different perspectives that I take from that.

And the first thing would be, as you mentioned, study design and the research side of things. And the first hurdle to overcome is the research ethics board. And the interesting thing is, as soon as you add exercise as an intervention, there's this fear that you know if I'm going to get somebody walking, you know somebody, you know somebody have a heart attack right from doing that. And so what's the safest way that we can, you know, implement some sort of interval training program? And so one of the things that people think okay, well, if we get them on the bike, okay, at least if they fall. Well, on a treadmill, it could be theoretical, you know, which doesn't really happen very much.

But it does happen. We've had it happen in our lab.

Yeah, it's certainly. That's funny, though, because I actually, when I bring in runners to do running gate assessments and my physio practice, I always say have you run on a treadmill before? Because you could be an incredible runner, but I've never been on a treadmill, so I always check that first. But yeah, I'd say, you know, safety things first in terms of making sure we can get through things through the research ethics board. But then also injury rate is always a little bit higher in runners than in cyclists and so if we don't want to have a large number of dropouts though that still happens if you've seen some of my other work and in cycling that dropouts will happen either way. We try to get people on the bike but looking from a you know, a physiology perspective and a coach perspective, there's certainly some benefits or certainly some direct translation to running. So in terms of improving fitness, we can, you can.

There's some studies that show that you can have someone do interval training either on cycling or running for runners and you'll still see an improvement in VO2 max. There's no direct studies that I've seen that that compare the difference. There's one better than the other, but we will see an improvement in fitness, but there's certainly some limitations with with doing interval training on cycling for runners is that specificity of the sport and specifically around efficiency and tendon loading and eccentric loading. And so in one of one of my studies we found that in untrained or even active individuals there's a significantly greater improvement in racing performance for running compared to train runners, and we speculated that it's likely due to just them learning how to run. So let's say you see a 5% improvement in performance. Maybe about 50% of that has to do with just them learning how to run and getting the mechanics of running over time. And so while we might see some fitness improvements, I still think you know interval training for runners should primarily be done via running.

Is there anything we can say about the interval structure itself, because that's what we're going to predominantly be talking about throughout the course of this conversation. That may or may not translate to from cycling to running. So you have a cyclist, we see this protocol. It's x by x minutes with x minute with y minutes recovery. We see that there's some sort of improvement in performance or some sort of physiological parameter. Is there any reason why a running coach shouldn't look at that design, that specific design that's done in a cyclist, and translate that one to one? Or is there some sort of different translation that actually needs to be made?

Because we have this conversation in our coaching department all the time. We're like oh, look, look, you know, look at this new study. It said that 30 second intervals are the magic intervals. Now you know which was? You know, last month there was three month, three minute intervals. Those were the magic intervals, and then three months ago it was seven minute intervals. But once again, whatever the magic interval, the genre is, they're typically done in cyclists, and running coaches kind of across the world will look at those studies and put their own translation on it. Right, okay, we need to take it one for one. We need to shorten it, we need to manipulate that recovery interval or manipulate the work to rest interval ratio for some reason that they have internalized. I was wondering what you had to say about that, since it is such a common practice to take research done in another sport and apply it to a different sport group, and that's running in this case.

Yeah, I'd say it depends factor.

That's what I always try to explain to my students that it's not always that black and white, but I think for the most part you can directly translate. If you're going to say, do four minute intervals on the bike, can you do four minute intervals running? And would you have the same physiological adaptations? Yes, so internally likely, you'd have the same cardiovascular and skeletal muscle adaptations, at least in terms of the physiology to you know, for octetative metabolism. But in terms of what you might be doing to the tendon and the physical load to the muscle, yeah, it would be different. And so let's say you've never done interval training before. It might be easier on the body to do it on the bike as opposed to running, at least in terms of preventing injury and then possibly for recovery. But in terms of the metabolic load, let's say, probably a one to one translation would probably have a similar translation

.

Yeah, Okay, I appreciate your perspective on that because, like I said, it's been batted around a lot and I've definitely seen people, like I said, put their own kind of spin on it and I've always been curious to see what other people think about it. So, now that we've got the caveats out of the way right, we're taking research that's predominantly done in cycling and we're kind of like moving over to running. Let's go for the jugular. You played into this classic ultramarathon cliche. We're going to try to bite off probably more than we can choose.

So the background on that and why I'm laughing is, as I originally resets, mike and I wanted to talk about one meta analysis that he just more recently produced, to which he played into the cliche and sent me two others that he did as well, that are all in the same, that are all kind of in the same sphere, and we're going to try to apply some broad brush strokes across all three of those because I think it's actually I think that it's, that it's relevant, and then dive into the nuance from from that. So the three papers that I'm going to mention are going to be linked up in the show notes and they all have to do with kind of the same theme Now, does interval design affect physiological parameters, maximum oxygen uptake, peak power output, as well as performance and I'm emphasizing the word performance intentionally, because we'll probably come back to that theme as this conversation goes on. But to start out with, are there any like broad themes that you can apply? We're going to do like a meta analysis of the meta analyses. Are there any broad themes that you can apply after like looking through all of these that are important to mention just right out of like, right out of the gate, that are extremely practical, that almost any athlete can kind of take away from?

So, with respect to interval training themes, you know, keep it simple, I'd say. I mean, we try to over complicate things and if there's anything that that that the meta analysis, the results from the meta analysis, show, is that there really is certain ways to stress, to stress the body, and it doesn't matter whether you're going to do, you know, a one mile or five or five kilometer run versus a 40 K runner and ultra, ultra distance race. It's you know what, what is it that we're trying to do? And there are certain types of intervals that'll help to achieve those physiological adaptations. And I think that's one of the first things to think about. You know, some people say, well, I'm going short distance, so I'm going to do one minute intervals and maybe progress two minute intervals, and then somebody might say I'm doing this longer stuff, so I should be doing eight minute intervals or whatever it is.

But really the idea is it's not based on the distance, it's what's the physiological stress that you're trying to achieve and what's the best interval to achieve that stress. So, for instance, if we're looking at central changes in terms of cardiac output and and changes in how the heart can actually pump the blood through the body, maybe longer intervals are the better way to go, regardless of of what type of race you're going to do. It's what, what's the objective that we're trying, what we're trying to achieve here. And so, yeah, I think you know one of the things overall is it's not based on the race, it's based on the type of adaptation that you're trying to stress on the body and that was actually a shocker for me that you know based on the interval or, sorry, the race distance. It's kind of irrelevant. You can do any type of interval training. You'll see the same improvements for short distance or for longer distance races, because you're just causing that certain stimulus for change. I'm going to.

I'm going to peel apart both of those just a second, just from the practitioner's point of view. Not that you can't play the practitioner's point of view because you are, but but I think that this is this is highly relevant. And first off, your theme of keeping it, keeping it simple.

We see all different types of creative and entertaining permutations of interval design.

Some of them will manipulate the recovery period and maybe even elevate the intensity of it and those are called, you know flow in intervals or you know you can. There's a lot of different like pieces of vocabulary on it and I always see coaches try to try to play to that entertainment factor by kind of coming up with these different combinations of interval length and then the intensity of the recovery period and then manipulating the intensity of the interval period. You know, from level 10 on the first interval to a level eight on the second interval to a level 8.7 on the second interval or the third interval, and so on and so forth. And I look at all of that and I just think it's complication for complication's sake and it dovetails into the second piece that you actually mentioned is that there is absolutely a cause and effect between the way that you construct the intervals and what physiological parameters that they actually end up impacting, and when I look at the mismatch of all of the combinations of intensity and duration and recovery intensity and recovery intensity and things like that.

I see that physiological mismatch come through with the interval design where it's stressing different components of the physiology because of the duration and the intensity and the manipulation of all of those, and so it's one of those things where there's first two themes that actually kind of comes through in practice. And that's not to say that you can't design some sort of I'm going to use a term that all the people are going to get pissed off because I know that they do this Some sort of like cockamani design where it's got seven different intensities and four different recovery lengths and four different recovery intensities and all that other stuff that are all kind of mismatched into one. But when you're designing things like that, you have to understand that you're touching on different pieces of the physiology that might have different outcomes and it might not be enough stress, enough workload across any one of those to actually make more of a difference. It probably makes a difference, but not more of a difference. I guess is what I'm saying.

Yeah, Actually I think the idea is it's what's the optimal programming to create the best stimulus for change and really exercises just a stimulus for change.

And that's all we're really doing here. So, if we think about it, there's two real types of interval training that people do, and one would be sprint interval training and then the other would be high intensity interval training, and it has to do with the intensity domain in which people are exercising, and I've heard some of your podcasts and so some of the. I think we're on the same page here in terms of how we would distribute exercise intensity. There's so many different ways to do that. I use the four domain model, and so we'll have moderate intensity, heavy intensity, severe and then extreme. So, in terms of those different domains, and so high intensity interval training would be, it'll be above your critical power, critical velocity. I'll just use that interchangeably here. So basically above your maximal metabolic steady state, but below the highest power that will still allow you to obtain a VO2 max, and I think that's important to distinguish between just power at VO2 max versus the highest power that you can still obtain a VO2 max. We can chat about that in a little bit.

But then after that, above that intensity in the extreme domain, is where you would perform sprint interval training and what. So what would be the if we were to look at those two different types of intervals, why would we do one versus the other? And so if we start with high intensity interval training and we're in that severe intensity domain again between your critical velocity and your VO2 power or speed at your VO2 max, intensity doesn't matter. You can exercise at the bottom end or the high end in those domains and you'll see the same improvement.

When I say intensity doesn't matter for racing performance it certainly does matter to change your VO2 max or VO2 peak. Intensity is related to that effort or to that adaptation. But it doesn't matter. Once you're in that domain and some of my findings from looking at all the studies on interval training, on time trial performance and time trial performance, I'd argue, at least in a lab, is probably the best way to measure performance. For endurance athletes it doesn't matter. But interval work about duration does matter. And so we say well then, how can I maximize my stimulus by increasing that interval work about duration.

And so what got me thinking about this first, and what my research was originally going to be looking at was, before COVID was looking at oxygen uptake kinetics how long does it take to reach your peak oxygen levels? How long can you maintain that for and at what intensities within that severe domain can you maintain that no-transcript? The literature, from looking at all the evidence, and the evidence only shows up to about five and a half minute intervals that the longer the interval work out duration, the better improvement will see in racing performance. So we might say, well, why doesn't one minute intervals worker, two minute intervals work? And if we we go into this idea of saying, well matters that you're at peak oxygen levels and Weirdly enough there's no evidence to show that that's the case, we just kind of use that as a measure. It takes about two minutes approximately to get the peak oxygen level. So if you're only doing two minutes about, does that mean you just reach that point now where you're at the oxygen level? If you're doing ten minute interval, is it gonna take you five minutes to reach peak oxygen levels before you actually do? Sorry, you only actually exercising at optimal levels for about five minutes, and so I don't know. I mean we are studies that look at that right now and unfortunately that was my pre covid research. But so what would be the optimal level that will allow you to get the most bang for your buck at high levels of oxygen? That's probably between five and seven minutes, somewhere in that range, maybe five or six minutes.

And so you know, we say, well, we're gonna manipulate these intervals. But why would we do less, less than that five or six minutes? Why do we do more if we're not actually gonna change, obtain the response that we want? And I don't just mean the acute Metabolic or physiological response, I'm talking about the adaptive response, because there is a disconnect actually between the acute responses in the physiological adaptation and so. Well, I might seem like I'm over complicating it in the simplest format. You know you should be doing intervals that are probably around five, six minutes if you're gonna do severe intensity exercise At any intensity that you'd like, as long as you're within that severe domain. Though I don't know about yourself, but I'm certainly someone who does running intervals as hard as I possibly can because I think it's fine. I'm one of those people. But you don't have to. I choose to do that.

Okay. So let's back up a little bit, because I think we went like right for the jugular in terms of now everybody has the perfect interval link, which is five, six minutes. Everybody's gonna go out tomorrow and do five to six minute intervals.

Our coaches are. All the coaches out there that are listening to this are gonna go out and re prescribe their intervals to five or six minute intervals and just we can cut the podcast right there. But let's, let's, let's back up a little bit, because I think one of the things we skipped over is is this concept that any intensity within this specific intensity range, it kind of doesn't matter. I first off want to better define and maybe describe what that intensity range is, and we use different ways to describe intensity is. We can use an RPE scale, we can use percentage of via two max percentage of like take threshold, like take levels, and things like that. Maybe we can go through a different, a few different iterations of what the severe domain actually is and then dive into why does it not matter?

Why does volume and we see this a lot kind of come through the meta analysis that you went through and we also see this cross a whole host of litter, literature, as you're aware of that volume, or time under load, I guess, is a better way to put it. Time under load tends to be the catalyst for the better, catalyst for adaptation versus the specific intensity itself within any one Specific bandwidth, bandwidth of intensity.

Let's go back to the first piece. You mentioned, severe domain. Let's put some guardrails around that so people can kind of conceptualize what that means from an intensity perspective when they start to go out and kind of like execute these types of workouts.

Yeah, that's, that's, that's a good, yeah, that's a good place to go, and certainly I wouldn't suggest people going out and just doing five minutes and it goes off to that. There's a lot to it and so for those of you you know, there's a little bit more to it than that that will be the social media snippet, because everybody will misinterpret it, so we'll pick some picks up the guy.

But I say so the lower end of that domain is. It depends on how we're measuring it, because there's so many different ways to assess it. But you know, if you're doing, if you run 10 K and about 35, 40 minutes, that might be close to the bottom end. You know, for some people it might be 15 K, so anywhere from about 30 to 60 minutes, and that range is a good Number, I guess, or a good range to say for where the bottom end of that domain would be. But theoretically it's, it's the highest sustained, sustainable level where you will have a steady state in oxygen and and any level above that. Now you can't reach a steady state, which is basically means that at high, at a constant workload, you're starting to increase the oxygen consumption, so you're becoming more and more inefficient, and so maybe something like a 10 K, but that depends on the person, I guess. And then, if we look at the higher end of things, it's really only about two minutes and and that you can maintain that intensity for and and and. Actually it's somewhat important to talk about that high end, because one of the the arguments that I've heard about the most recent meta analysis that we published was well, why did we measure what peak? And I'll use what peak interchangeably with velocity peak and so well. There's different protocols to determine this, but the high end is at that two minute. If it takes you, two minutes is where you just reach your, your VO to max and then you actually have to stop exercising because you physically cannot go anymore. If you're able to keep going, then you haven't hit that, that what peak, or we will watch a. Typically we would call it your maximal aerobic power or maximum aerobic velocity. And so you know we range anywhere from 30 to 60 minutes on the bottom end, in about two minutes. On that, on that top end, in at least within that severe domain, and as long as you're exercising within that domain and I'd say you want to be at least 5% above or 5% below, because there's always this error rate so as long as you're somewhat in the middle there In terms of looking at racing performance, there won't be a different.

Based on intensity alone, you'll see the same improvement. But there is something to do with what you mentioned around total work or total volume, and it's not just how much volume you do in a session. So let's say you do, you know, 20 by one minute intervals. So what we say 20 by one minute intervals or four by five minute intervals we've accumulated the same amount of volume, but what's happening metabolically during each one of those sessions would be different, and so that's where, yes, it is important to consider how much work we do, but how we distribute that work. That's when that starts becoming more important. And interestingly it's there is no correlation or no relationship between total, total volume in a session and change in performance. It actually it's more about the duration of that work, about itself.

For those intervals, yeah, so then everybody's going to ask what's better? Should I go do 20 by one or four by five?

Yeah, well, so that's the thing. So if it takes approximately, you know, two minutes to reach a VO two peak, you know what are we actually achieving here? And so, regardless of that acute response that I'm talking about there, in terms of performance gains, probably five, four by five would be better. But again, I'll always say this is why it's like don't take that is there, is there's the it depends factor, because there's a difference between and Steven Seiler and I spoke about this several times there's a difference between finding a way to maximize your time At VO two max versus optimizing it.

And, and the read, and what I'm getting at there is you can overdo it, you can allow me to achieve 30 minutes of time above, but do you really need that stimulus to cause the change? Like, how much stimulus do you actually need? And then, are you going to get sick, are you going to get hurt, are you putting yourself in a much bigger hole that you can't train for three days? And so that's why it's like, well, should we do four by five? Well, I guess it really depends on who you are and where you are in your training.

Well, Because people hate that answer. I'm going to pin you down on this eventually. So in the reason people hate that, it like it depends on it and blah, blah, blah, but it always depends. I tell my coaches this actually, if you're going to use the, if you're going to use the out, it depends. You have to come back with it depends on, and you better be able to say it depends on for this group of athletes or this type of athletes or this phenotype of athletes, and here's how we're going to change things to pin based on that presentation.

So we have this general construct and let me, let me try to stylize this a little bit. If I'm taking a little bit too much liberty with the interpretation here, please, please, course, correct me that if we're talking about doing intervals, in this severe domain we should be favoring slightly longer intervals. If we're talking about the bandwidth of interval duration from one minute to five or six minutes, the construction of those workouts should favor the longer type. When you look at the whole basket of things that you can manipulate, right, that's a, that's a broad, like a broad overview. Is that a reasonable, reasonable stylization and summary of what we were just talking about?

Yeah, yeah, that's definitely correct.

Okay, so then, within that, within that it depends now that we've got the shade of the, of the of the entire interval prescription towards the longer piece of it what are the things that it might depend on? Is it the experience of the athlete? We just mentioned that we can calibrate the intensity based off of, you know, their 10k time, their 15k time, and that might mean something different depending upon how fast they're actually that they're actually finishing that. Is it the caliber of athlete? Is it the experience of the athlete? Is it some other variable that we can change this shade on to get a better fix on this? It depends. Answer.

No, I'm happy that we're gonna. We're gonna dive a little deeper into that, because it is important to talk about that. And Training status certainly does does matter. And you can be completely untrained or just an active individual, and when I say active I mean somebody who may run, may buy, but they're not on a specific program, that specific to a mode of exercise. And so let's say, the difference between somebody who's trained and untrained would be that they exercise to a specific mode. If you're untrained, you can do anything you want In terms of producing a stimulus for change. Now I'm not saying, go and you know, run for five seconds and that's it for the week. I mean, you know, you can kind of do low intensity exercise and you'll probably see even some of the adaptive responses that you'd see with high intensity, because it even low intensity for you is going to be a huge stimulus.

I so love that that perspective. By the way, you could do any, almost anything you want, as long as you don't screw it up, and they're going to improve. And it's actually hard with those untrained audiences To say this is better than this and then that then is better than that, because they have so much room to improve that optimization component that is just so prevalent in today's world. We're trying to optimize everything right. That optimization component doesn't really have the chance to filter through because the bandwidth from top, from from where they're To the top there, their individual top, is just so big.

Yeah, it's it's. It's interesting because consistency is probably the most important thing, if I was to say anything. We talked about so much intensity and my work is all around exercise intensity and a little anecdotal story here. I'm more of a runner now than a triathlete at this point and I recently, but I normally run about six days a week and I might do intervals once a week and the rest of the time I might be doing 1015 minute run and the amount of improvement is that I've seen with just again, based on my previous training background as well. But just what type of stimulus I personally need and still able to go under 17 minutes for 5K.

And so you have to start saying well, what kind of stimulus do you need? But of course anecdotal and more personal there, and being a researcher I'm always anti-anestotal evidence. But once we get into somebody who's trained, that's where the it depends thing matter, and so one it depends on your training status. The next thing I'd say is well, what's the goal that you're trying to achieve here and where are you in your training program? And that's where training intensity distribution might start to come in. But so if we're going to say what's the goal that you're trying to achieve, we've been talking about high-intensity interval training. So training below the O2P cannot sprint interval training which is above, if you're just starting out for the season, and we're trying to say, well, what's the objective that we're trying to do here? And if we say sprint interval training might lead to greater peripheral adaptations, whereas high-intensity interval training might lead to more central adaptations, we can talk about those.

Obviously that doesn't mean that one only does, it only does one and sit only does the other. It just maybe there's the research is suggesting, maybe there's a one that'll favor one area than over the other.

So I would say, well then, what should we be doing first? Even and hopefully I'm not jumping the gun here, but that's just where the it depends factor comes in. And if peripheral adaptations tend to occur first and they do we tend to see that you'll see changes in the skeletal muscle, changes in mitochondrial adaptation. However, we wanted to find that angiogenesis so growing new muscle, the vasculature in the muscle, tends to occur earlier than central adaptations like changes in the cardiac structure, function, plasma volume, those types of changes. Then why not try to hit the peripheral adaptations first? Because if we can stimulate those peripheral adaptations and maybe get more oxygen into the skeletal muscle and maybe we're able to use more oxygen once we're able to get more oxygen there, rather than the other way around where if we do hit first, we'll still get some peripheral adaptations but we're not seeing enough of a stimulus here, how can I optimize my training?

So that's where the it depends factor comes in. Should I be just doing these five minute intervals? Or maybe I should start doing something like sprint interval training first for a little bit and cause some sort of adaptation and then maybe facilitate more of a central adaptation later, in case, of course, there's no literature right now, that period I sit and hit. There's a little bit of stuff out there, but, based on the physiological responses, maybe it makes more sense to structure things a little different. So one would be what's your physiological goal? Peripheral versus central adaptations? Another thing would be the type of athlete that you are, and then the next thing would be where are you in your training cycle? If you're getting close to racing, then maybe we're not trying to cause the central, peripheral adaptations. Maybe we're trying to learn how to race and use substrate. What rate do we use substrate and what rate do I need to know how to refuel and give take on water? So yeah, there's see, it can get somewhat complicated, but yeah.

Well, it kind of comes back to this overarching periodization structure that I always mentioned, because we tend to once again over complicate it between pyramidal and polarized training and specificity phase and preparation phase, and not to say that any of those are not valid, and I'm trying to be too flippant, but if you wanted to, if you wanted to kind of like stylize it across a broad array of athletes, is you're doing the things that are most important to performance, the closer to when you want that performance to occur, and you're doing the things that are least important to performance, or maybe even supportive like might be a better word supportive of that performance as far away from the event as possible. So, in your whole, you know, teeter, totter of central versus per, not that it's exactly like that, but that in this whole balance between central and peripheral adaptations, if you think about it through that lens, what's more important than what's more important to performance should favor those, as the favor those types of adaptations, the closer to the closer that you, the closer that you get to the, to the event itself. I want to. This isn't a hard pivot, it's like an angle almost. We're going to tack the sales, so to speak. So first time. I've pulled out a sailing analogy in this podcast. So whoever had that on their bingo card finally gets to cross it off.

I'm going to, I'm going to pivot just a little bit and and and kind of focus on what I wanted to originally focus on when I reached out to you and that was this one specific meta analysis, and I and the title of it is just to get this out of the way is the additional effect. I'm going to actually put some emphasis on this because I think it's important the additional effect of training above the maximal metabolic city state on VO two, peak W, peak time trial performance and endurance trains in endurance trained athletes. And the reason I think it's so poignant right now is because we're going through another thought shift. I was going to say paradigm shift, but it really isn't shifting all that much amongst the practitioners. Attention shift that's what I wanted to say. We're going through an attention shift where there's a lot of emphasis put, put on low intensity zone to work and that's all the work that you need to do and things like that.

This meta analysis kind of looks at how this, how adding this specific intensity to one's training program, affects this kind of basket of variables, and so I think it's an interesting conversation topic right now, because one of the things that has kind of emerged in this whole zone to talk kind of amongst a certain amongst some of the people that are discussing this, a lot of whom I've had on this podcast, is that the incorporation of low intensity volume seems to have no ceiling as to how it actually benefits athletes. So you add 10% and it still tends to benefit them. You add another 10% there still seems to benefit. You see, you add another 10%, it still seems to benefit, and the, the, the. If you draw that logical conclusion out, you do as much low intensity volume as possible and you can never see an asymptotic point or a point of diminishing returns within how the athlete actually actually improves.

I'm not saying that I as ascribed to that, I'm saying that's one of the, I'm saying that's one of the, the thoughts that is kind of kind of prevalent in this and in in this meta analysis, kind of looks at, well, what if we just take this, this, this, this kind of base of work and we just add high intensity interval training to it, what actually, what actually happens? So first off, I kind of want to know your thought process, like going into looking at this specifically because it is kind of a very specific construct. And then what do you actually? What you actually found from like combing through the literature, that that that's related to this topic?

Yeah. So it's interesting because there's a lot of literature on there that out there that that looked at the difference between, you know, modern tensor low intensity versus high intensity training, and typically that would be in in untrained or just active individuals or sedentary individuals. But in trained individuals, while you might want to investigate that, you'll never be able to get an athlete or a trained to say, okay, I'm just going to do two sessions a week for 20 minutes, like it's just not going to happen, Though I mean we can. Yeah, it's not going to happen, and so it's it's. It's not feasible, at least from a recruitment side of things. But then also in terms of what we need to do to prove performance is always going to be this combination of multiple intensities low, medium, high, et cetera.

And so initially I wanted to quantify the effect. I wanted to say, well, what kind of improvement would we see? And everybody studies the VO2 peak. I'm one of the first people to meta, meta analyze. I don't know if there's other meta analysis other than my work that looks at time trial performance. Being a coach, I cared about that more and so I I wanted to look at VO2 peak and time trial performance and then what peak or W peak, and I'm going to use that interchangeably with velocity peak. It's just the combination of the different sports. Well, that so that that the that power that's achieved at the end of your test, we might as well look at that. And, interestingly, we also wanted to look at changes in your critical velocity or critical speed. And at least in the studies that met the eligibility criteria, there weren't any, or there might have been one, and so we didn't get to look at that outcome.

And we had quite an interesting result. It was we saw an improvement that adding intensity led to improvements in in VO2 peak, so the amount of oxygen that you can consume. There was a. There was a significant improvement. There was probably between three and 6% overall, so about two and a half milliliters per kilogram per minute.

Training status when I say training status in this case they're all trained individuals, meaning that they were all doing a, a structure training program, ahead of time, but some were recreationally trained and others were competitively trained. We'd see the same improvement regardless, and so that's interesting to see. You'll see the same improvement in performance. But we didn't. We didn't see any any difference between the two groups in terms of change in racing performance, and it's important to say that, but it doesn't mean that there wasn't an improvement between from one intervention or another. What I was comparing was is one better than the other? And we didn't see a difference between the groups. But there's some caveats here. So, first of all, we only looked at a single mesocycle, okay, so what's just, you know, over a short period of time, relatively speaking, and I think that that might speak to why we didn't, one of the reasons why we might not have seen a difference between the groups.

Why is that? Because that's when I look at the study design length. One of the filters that I use that I know that you're kind of going to as well is how long the intervention is compared to the things that you are measuring and the time course of adaptation that is necessary to elicit a change in the things that you are actually measuring. So let's give just a little bit of background on that piece as well.

Yeah, so the studies range from, I think, two to 12 weeks in duration and of course that's a huge range relative to training. I mean two weeks, we think. Are we going to achieve anything at all? But we do. Interestingly, we will see physiological adaptations and changes in VO2 max or VO2 peak, but interestingly we won't see an additional improvement after those two weeks in VO2 peak. We've kind of in a single mesocycle. Let's say you're not going to see a difference there. But if you're already trained and it's already hard enough to see an improvement in racing performance, are we necessarily going to see a change even just over that period of time, even 12 weeks? And of course I'll say it depends. It depends on so many factors. But really we're just looking at a single mesocycle so we're not changing anything. They're just doing the same program for 12 straight weeks.

If it is on that high end, at least the way that the study was described, I can only go based on what I get from the literature and so I mean that certainly could be one of the reasons why we didn't see a change in racing performance. And I ran a regression or a correlation of about 250 data points individual participant data points, trained individuals to look at baseline VO2 and change in VO2 with respect to time trial. So, for instance, what I'm saying is is the percentage change in VO2 peak related to the percentage change in time trial performance? And the answer is no, and that might sound shocking, but there's a difference between is there a relationship between your VO2 peak and racing performance versus. Is there a relationship between the change in VO2 peak and racing performance? And there isn't, and is it? I think it's. Is it Paula Radcliffe who has an incredible marathoner who actually had a relatively low VO2 peak but kept on getting fast? And so maybe there's other variables or physiological variables that might speak to that.

Yeah, and the common story that gets pointed out is her running economy just got better over time and she learned how to race. And one of your colleagues now that I'm thinking about it on this paper, steve Seiler, actually has this really great graph that I really that I repurposed in my book that just showed how physiological parameters and performance change over long periods of time. So we're talking like three to four years and what we see is is VO2 max and other physiological parameters tend to increase very quickly once an athlete starts training and then plateau fairly quickly as well over long periods of time. But yet performance can still improve. And so what is that saying? It's saying somehow the performance is I'm gonna use the word decoupling from the individual physiological parameters.

When you broaden that lens out over three, four, five years. And certainly we see that observationally within athletes where we can bring them back into the lab. I mean, I've got great data on this from our lab here in Colorado Springs where we test athletes over and over and over and over over a sometimes a 10 year period and those physiological variables they kind of like go up and down and it's just based off of the training status of the athlete at the time, but they can continue to see better and better performances because performance is more like factorial right. It's even greater than the amalgamation of the physiological variables. There's other variables that kind of go into it as well.

I would encourage the listeners out there, before we change topics, I would encourage the listeners out there to go and go specifically to figure three in this paper, the force plot that you put together. Even if you're not that familiar with force plots, you can take a two minute Wikipedia orientation and kind of get to the summary of what Michael's just originally talking about in terms of how these, how these variables either do or don't move when we look at adding high intensity work to a training program. Because it's very beautifully illustrated and I just have to give you kind of kudos on that. It was something that I think that athletes can understand, even if you're not used to like looking at research.

And one key point about that when you're looking at what the outcome measure is, the standardized mean difference, and the simplest way of thinking about that is just how many standard deviation of improvement or difference is there? And I think it's always for VO2 peak it was 0.44. So about half a standard deviation difference. And so that's how, when there was outliers, I knew when one study showed a two and a half standard deviation greater difference, something is a little off here. So yeah, that'd be amazing.

You're always gonna find that when you look at a basket of studies. So I would encourage the athletes, I'd tune them to this right here, because it kind of has the whole array of study and interval design construction everywhere from 30 second intervals to eight minute intervals was kind of the longest one that I saw that was included in this group, is that correct? Yeah, so it has the whole range and I think it kind of illustrates it really well. So we've kind of been batting around the kind of the conclusion of it, not to trivialize your work, but what's the nickel version Like? What are the athletes gonna kind of like take home with this and take home with this in terms of should we actually add some type of interval construction to our training program and how is that additive to either the physiological variables and or the performance?

So, yeah, I'll try to keep this simple, cause I can certainly make it complex, but yeah, I think you should. I think you should definitely add high intense interval training to your program, of course, depending on where you are in your training, et cetera Just because we didn't necessarily see an improvement in these results. Right, and meta analysis is only able to analyze the results based on the available data, so we need to take that into consideration, and so the first thing is is yeah, you should add, you certainly should add high intensity training, maybe a couple of times a week.

The other thing that I think was very important to note was, at least methodologically speaking, regarding that the work was sample size issues are a huge problem, and that might lead to why we're not seeing significant differences between groups at times, depending on the studies that we're looking at.

Interestingly, the power or the ability to detect a significant difference between groups in the different studies was only about 16%. You need 80% when designing a study to determine what sample size that you need, and it was only 16% average across studies, and so I think the sample size is range anywhere from five up to 20 per group, whereas you need 81 participants per group to determine that effect of almost a half a standard deviation for VO2 peak, and so really really think about that when we're looking at the Stepped-Oast study, which was, of course and I refer to the Stepped-Oast study because a lot of people out there are looking at one study in particular, or they talked about this group, which was an incredible study at the time but there's only about four people per group in that study, and so there certainly could be issues with sampling error et cetera. Not that I'm saying anything negative about the study it was a great study. It's just how we interpret the results. I think it's just where we need to be cautious.

The Stepped-Oast study, for the audience is not familiar with it. What is the study? That compared kind of five different formats right, 12 by 30, 12 by 60, 12 by two, eight by four and four by eight. And what you're mentioning is is that when you try to come up with all these different permutations, you gradually whittle your audience down to very, very few and it's hard to come up with statistical significance whenever that's the case, or it's hard to interpret the significance when that's the case.

Yeah, you have quite a wide standard error there, so we were not really able to narrow things down, but the study was done in 1999, which were published in 99. So it would have been a few years, if one of the first studies out there of its kind, so it's an incredible study.

Yeah, I remember looking at that when I actually first started coaching and thinking that I was a genius because I could derive something from that. If it is, things come out, you realize, oh, wait a minute, there's a bigger picture to this, okay. So now that we've got this, I kind of want to take this to like level two or two. And we're kind of like both coaches here, and one of the things that we're commonly, one of the things that we're constantly trying to turn the dial up on with the athletes that we work with across the entire lifespan that we work with them, is this concept of progressive overload. And we go all the way back to fundamental coaching 101. In any sport, whether it's strength training, aerobic training, whatever we have to apply a greater and greater stimulus to achieve greater, to achieve more and more progress.

Within the concept of this high intensity interval training, some of the things that we mentioned is, as long as you get in the right zone, kind of the interval length matters the most right. The precision of the intensity doesn't matter nearly as the duration of the actual interval. But when we're looking at athletes and let's say we've worked with an athlete for two years and we've got a particular interval construction that we actually like, that we see adaptations for whatever. How do we actually go about progressively overloading that athlete?

Do we increase the intensity? Do we increase the time under load? Do we increase the interval length? Because a lot of athletes are gonna think about that. They're like, hey, I've done, like you know, five by five minute intervals, or four by five minute intervals for forever.

Do I need to manipulate that, as I have two, three, four years of experience. So what can you say to that? Just through the like, your coaching lens more than anything else, if we have athletes that have gotten to this stage of progression, how do we make sure that they continue to progress after we have seen that initial bump?

That's a very good question and I'd say the progressive overload here wouldn't necessarily be around the structure of the interval session itself. It would be more around the structure of their whole program and that could be how much stimulus can you handle in a week? So maybe somebody like me can handle one and a half sessions a week right now of hard stuff, and also maybe I can only handle about 10 minutes, so maybe two about doing much more than 20, 25 minutes might not be necessary. But you know, one thing would be you know, okay, if I already got what I needed out of these five by fives, is it good now to go back down to doing 30 seconds sprints or 200, I'd say 200 meter sprints with four minutes, or doing some sprint interval training? Is it time to cycle through that and constantly cycle that way?

But another way that I'd suggest for progressive overload, which I think I was hinting at, is if two sessions a week you recover really quick, does that mean we're able to put in more work? So maybe they can handle three sessions per week, and I'm not, and I'm always nervous to say that because three is a lot. Three is a lot, yeah, three is a lot, maybe to prevent injury. That's where you might want to bring in cycling if you were to do that. But I'd say adding more time might be beneficial. We don't know. I think a literature suggesting 20, 25 minutes, maybe around 25 minutes, is the most amount of time at least that's been studied for work during an interval session. But maybe, okay, we've stressed the body enough today and I recovered within a day and a half. Maybe I can stress it again, possibly. But I'd be nervous to say to someone start doing three or four interval sessions a week without them one getting hurt or two going deep into the hole. But if anything, it'd be really around the structure of the program cycling between the stresses that you need.

Okay, if five by five stress the cardiac response, that much, then switch over to sprint interval training and there's a way, at least anecdotally, that I help athletes think about that. And there's a difference between are your legs getting tired versus are you breathing crazy heavy? And if you're doing these intervals and you don't feel your legs at all and you can't handle it in terms of your respiratory response, then typically that's where I'll prolong how many weeks you might be doing, let's say five by fives or four by six and so, rather than it just being three or four weeks, maybe I'll say, okay, we'll do a recovery week and then do another session. Keep stressing that system and at some point what I've noticed is okay, I'm not there anymore, my legs are starting to get tired. Okay, let's start stressing the peripheral side of things and doing some sprint interval training for a couple of weeks. So I think it's more the general structure of the program as opposed to the interval session itself.

Yeah, I mean, I'll take it from the other perspective. There's only so much time under a specific load that an athlete can handle. And if you think that you're just going to add time, let's go from five by five, let's just do something completely crazy Go from five by five to like eight by five. You're moving the intensity domain too much, right, because there's only so much load that they can handle under that. And if you're moving the intensity domain, then you're kind of changing the purpose, right, maybe even the physiological outcomes, to a certain extent, of the workout itself. So when you're looking at what to progress, right, to achieve a different type of overload, to rephrase what you're saying and I'm in- an agreement with this.

You have to look at the weekly or even maybe even the monthly or even the quarterly architecture of how you're doing that, and you can do it a lot of different ways. You can, like, increase the density of the hard work, which is what you're describing, going from two workouts to three workouts per week, so that increases density as well as increasing, like, the total amount of time when you aggregate it over the course of a week or a month. Looking at those types of manipulations versus just adding more, which that's the hammer that we always want to pull out right as endurance athletes.

Yeah.

Just more, more volume, more time and intensity, more everything to try to overload things.

Yeah, because what you're, that's exactly. It is what's the stimulus that you're looking for and if you're in that domain, you're producing that intensity domain. You're producing the stimulus that we're hoping to achieve.

I can tell so from a practitioner standpoint the way that this actually works itself out when I get a really good athlete in the door. Almost always not always, but almost always the. The first and maybe even the only manipulation that I make is looking at what they do for an entire year and just putting it in a different order, not more, not less, just taking the same hours, the same time and intensity and all that other stuff and just kind of restructuring. And the reason for that is is they're good for a reason. They got to this level for a reason.

Adding more isn't necessarily going to make them, you know, a better athlete, just simply doing a different, a different kind of clustering or combination or structure of the same. It's typically the, the first off, it's the less risky fruit to pick off of the tree. Because when you talk about managing injuries, particularly in a in a running, in a running context, you just have to keep total, total training availability kind of in the back of the mind. But I I find that that's the easier thing to do to get additional adaptation, particularly with a good athlete, as opposed to just hammering on 10% more volume Not in all cases. Sometimes I get some easy, low hanging fruit and just like let's just add 10% volume and then we can kind of we can kind of get that. But in a lot of especially lead athlete cases, the first thing I'm doing, or the primary thing that I'm doing, is a training reorganization versus just adding stuff.

Yeah, I'd say that's certainly something that I look at too, because a lot of times they're tired and so it's just how are you structured? Can we make it so we just exercise, we pray to the stimulus? You need to recover a little, so let's just shift the stuff that you're doing so you get a little more recovery time.

Yeah, okay, we're going to wrap this up a little bit before I do. Is there anything else you want to add? Before everybody goes out and changes their entire programming to five to six minute intervals twice per week, which is kind of the thing that we like. We like highlighted, but I want to. I want to make sure that we bring some kind of balance and in professional context to it, since both of you and I are coaches. Is there anything that you want to add to the dialogue? Before we leave the listeners with the outro of the show notes?

Yeah, I'd say you know one talk to your coach first before you make any changes. I mean it sounds funny to say, but that's actually true, because just because something sounds like it could work doesn't mean you need it or you should be doing it.

Maybe that's a physiotherapist in me saying okay just give you an exercise and say oh it'll be okay you got to cover my butt here but I'd say, think about what your goals are, make sure you find out where your limitations are and try to address those. And if that means that intervals can help you do that, then yes, it could be worth bringing them in. But above all all else, I'd say consistency. You know, even if you're just getting in a little bit of exercise every day and then doing a few things to make some changes, that you know that's probably the most important thing, that consistency.

Always bring it back to the basics, right? Yeah, perfect. As I mentioned earlier, I'm going to link up the in the show notes specific links to these, these three papers. But if, in addition, what I'll add is is what we're going to go over right now, how can athletes get to know a little bit more about you and the work that you do and perhaps even get in touch with you if they have questions about anything?

Sure, I have a website. It's evidence based coaching dot CA and my contact information is on there. There's a little bit about me and and some of the stuff that I do. It's yeah, and so some of my literature or at least access to my literature, where you can find it is posted there as well, and my email address is on there as well.

So if you check out my website, it's there and Well, I encourage athletes to go and check out and the coaches to go and check out these papers. I think it's great context. If you're trying to design training for an athlete, we'll never learn the end point of all of this. There's always going to be different things. I was just reminded like old school Bronc Blot right Kind of our BA sorry of my French enunciation is typically pretty terrible Kind of started all this and she's an ultra runner right, a trail runner, right she wants to.

Was it Zagama in the 80s? I think it was something like that, one of the classic trail? It was Zagama. Kind of started all of this right, and what structure is better? So it always comes full circle. We're never going to learn enough about it. But I sincerely appreciate your contributions to the space because something personally that I became very interested in when I became a coach, but as I mentioned during the podcast, it's also topical because these different permutations of intervals and volume matters more and intervals matter more always kind of come up and we need to. Whenever that hype cycle swings one to one side of the pendulum or the other, we always need to realize that there's a balance of research that's out there that we can draw from and because meta-analysis always do a great job of bringing that balance kind of back to this, back to a consensus that we have kind of come to appreciate over many years of practice and looking at things.

Yeah, great Thanks. Thanks so much for having me on. It was a great great chatting with you.

Yeah, this is fun. There you have it. There you

go. Much thanks to Michael for coming on the podcast today. Always appreciate his insight as both somebody who is in the scientific community as well as somebody who's actually a practitioner.

At the cold face of prescribing these actual interval workouts for athletes, that combination I have always found fascinating is an and I think is an absolute killer in terms of how effective they can be within an athletic population. Whether it's cyclists, triathletes, runners or ultra runners is the case with this particular audience. I hope you all enjoyed this conversation and, if you did, please feel free to share it with your friends and your training partners If you think that it is going to make an impact on what they actually do. If you have people that are confused about interval structure, I would tune athletes into this particular podcast, as well as some of the previous ones that I did with Steven Seiler the esteemed Steven Seiler and I think that if you listen to both of those kind of in combination, it'll give you good direction on what to do with your training.

All right, folks, as always, I appreciate the heck out of each and every single one of you. Like I said earlier, thank you for putting up with a little bit of the delay in the podcast. We have got a lot of killer content coming out in the very near future, Some roundtables with our coaches, one on the business of coaching. That's one that I am very much looking forward to actually getting out in the wild. But until then, you guys will have to keep listening and, as always, we will see you out on the trails.