Science and Application of High Intensity Interval Training [transcript]

Written by Christopher Kelly

March 30, 2019


Christopher:    Paul, thank you so much for joining me this morning. I am delighted to have you for the second time. The last time I interviewed you was with Dr. Tommy Wood. I will link to that episode in the show notes that you can find over at A lot has happened since the last time we talked, Paul, right?

Paul:    Totally, but I can remember that podcast. I remember, I think I was outside. It was the start of a summery day. It was fun recording outside but we had a great conversation. I was writing the book at that time.

Christopher:    Right. So, that's what I was getting at, is that you were in -- I caught you at just -- I just reached out randomly and said, "Paul, do you want to do a podcast on high intensity interval training?" And you said, "I'm in the middle of a book. Can you talk to me--"

Paul:    That must have been like two years ago. That just shows how long the whole thing took to get to today because it's only recently been published. Oh my gosh, what a process. It definitely took two times or more the time that I thought it was going to take me when I originally agreed to do the book.

Christopher:    Wow. August 10th, 2017 was when I published that. We probably recorded a few weeks before.

Paul:    Yeah.

Christopher:    You're in British Columbia right now. How's the weather there right now?

Paul:    We're in kind of the end of winter, beginning of spring and we had an epic dump of snow in the big ski hill here at Revelstoke Mountain Resort. Yeah, just lots of snow outside and epic, epic skiing. That's what we're known for here. Big mountain skiing. It's pretty sweet.

Christopher:    Oh my god, you're making me jealous. I didn't get out this winter. What's your thing? Do you ride big fat paddle skis and do splitboards or something like that?

Paul:    Yeah. I'm just all mountain skis. I'm a hack but I have a lot of fun on the big mountain here.

Christopher:    That's amazing.

Paul:    Yeah.

Christopher:    And do you do your high intensity interval training on the show?

Paul:    Yeah. Well, absolutely, actually. It's incredible what a high intensity stem downhill skiing is.

Christopher:    Oh, downhill. Really?

Paul:    Yeah. Oh, yeah, so downhill, for sure. My legs are absolutely burning after some of the runs and stuff that we do like with super steep and extreme and, yeah, it's pretty awesome. In terms of the strength and the neuromuscular component that you get with the downhill skiing, it's epic. And then, yeah, I guess, you were thinking that I was more the Nordic guy. I do do the Nordic because, well, I've just kind of started too since I moved in here. It's great to go back and forth between the two. Winter training here is actually quite good.

Christopher:    And then what do you transition into once the spring finally springs?

Paul:    Yeah. Again, the other thing that typical mountain resorts are known for is the mountain biking as well. Like yourself, Chris, into the mountain biking and my sport is triathlon from the past so I still just always swim, bike and run. Yeah, there's good means of doing those, the swim and the run as well around here.

Christopher:    Tell us about the trails in Revelstoke. I've never ridden there. I've ridden British Columbia several times and I think it is my favorite place in the world to ride. But what are the trails like in Revelstoke? What kind of bikes do you ride? Is it big and gnarly and you've got a big full suspension bike?

Paul:    I guess, it's full on suspension but, yeah, it's just a giant. Nothing super special, does the job, and the trails are absolutely epic here.

Christopher:    Okay.

Paul:    There's a lot of professionals that come in here and hang out, keep it on the down low. Revelstoke here probably doesn't want me letting everyone know but the mountain biking is pretty unreal. I live here. I'll never get through all the trails that actually exist. It's one of those things. It's just they're everywhere.

Christopher:    I could definitely live in Canada. I think you're probably understating the technical nature of the trails. I found that to be my experience riding with Canadians. They're like, "Oh, yeah, it's fine." They don't realize what it's like in the rest of the world. Here in Santa Cruz, there are definitely some technical trails, but for the most part it's buff and loamy, and you could almost ride a hard tail. When I ride in Canada, there's like four-foot drops onto bunch of roots and rocks and skinny bridges and all these crazy stuff.

Paul:    That's absolutely right. You describe it very well. That's my experience too when I go to other places in the world. There's just nothing compares to what the level that exists here and that you almost need to be at to be able to, I guess, appreciate some of these rides and stuff that we have. It's awesome. If you're into it, come on up.

Christopher:    Yeah. I mean, I love the community. There's a certain culture around the mountain biking in Canada that I've not seen anywhere else either. It feels like it's really part of the community. Everybody is contributing to these fantastic trails. Whereas in certain parts of the Northern California that I won't mention, it feels like a bunch of rich people that are doing their best to try and keep mountain bikers out for whatever contrived reason.

Paul:    Yeah. You said it. You said it, man. The community here is really something. It's like I've heard it's like how many communities were 20, 30, 40 years ago where there's just salt to the earth people willing to give you your time and, yeah, we all just go out in various groups and whatnot to build trails. It's kind of cool.

Christopher:    That's amazing. I hope I make it back to Canada very soon.

Paul:    We'd love to have you any time, man.


Christopher:    Yeah. Sold.

Paul:    Sweet.

Christopher:    Let's talk about high intensity interval training. I'm going to assume that people didn't listen to the first episode and even if they did I'm sure they can't remember. I think there's no harm in having something repeated. That's kind of stuff starts to stick is where you hear it for the second or third of fifth time. Can you start by making the case for high intensity interval training?

    It sounds like a stupid question. And the reason I ask it is because many of my listeners, and myself included, will have gotten great benefits from following, a going slow all the time approach. I really don't want to misrepresent Phil Maffetone. I know that you know him personally. I hesitate to even say exactly what that means because I don't want to misrepresent him.

    But let's just say, it's just surprisingly effective keeping your heart rate say 140 beats or less. But recently, I've come to appreciate that perhaps this approach is not optimal for athletic performance but rather is medicine. So when you're a mess of a human and you totally destroyed yourself, then, the MAF method is a fantastic medicine for helping you recover your health but it may not be optimal for athletic performance. Maybe I should just stop talking now and ask you that question directly. Can you make the case for high intensity interval training?

Paul:    Yeah. There's some good thought train there, Chris. Maybe just to start we'll define high intensity interval training. High intensity interval training is defined as repeated bouts of exercise that would be above your anaerobic threshold. That's the, I guess, the level of intensity that feels hard or heavy and is unsustainable for more than 30 to 60 minutes. In the technical jargon, we would call this our critical power or our critical velocity or your anaerobic threshold.

    By definition, HIIT training itself actually has to be above this exercise intensity for periods. It's unsustainable work. What does that do? That elicits a number of important physiological phenomena to occur. One is you're recruiting your type two or larger motor units which are really important. I guess, if we want to think about the health and longevity angle on this, that's really important because these are the motor units that decline with aging. They become more and more deceased, I guess, as we age.

    So, actually, giving these units the stimulus to remind them that, no, we're not ready to die yet, thank you very much, we're still using these. That's the first one. The second one, I guess, big rock in terms of HIIT training and how it might differ from MAF training or low intensity aerobic training would be the fact that it elicits a cardiovascular, cardiorespiratory stimulus that, I guess, targets maximal stroke volume, maximal ventricular filling.

    Again, just like the stimulus that is hitting those larger motor units, you're telling the heart that you would like that cardiac output to be maximal as well and to keep that stimulus to maintain your VO2 max. Many of us will be aware that VO2 max is a key, again, indicator of health and fitness. So, I think those would be the two big rocks in terms of maybe what HIIT training, a regular dose of HIIT training gives us that your standard MAF training would not.

    I also need to back up a second and say, guess who the health section in chapter seven was written by and that was Phil Maffetone. Phil Maffetone is a great colleague of mine and he's written chapter seven in this one and that really deals with, like he said, Chris, some of the health and, I guess, wellness aspects of, I guess, stress and why the MAF training is important. Again, acknowledging -- Phil, he gets this a lot and he feels he's been misinterpreted many times.

Christopher:    You see, that was my hesitation. I felt that with Phil, that he feels like he's frequently misinterpreted.

Paul:    Yeah. He's an author in my book and he lectures in our course. He's well and truly aware the benefits of HIIT training. His angle a little bit more is that you can get too much of a good thing and he's absolutely right. Remember that HIIT training itself is also a stress. A stress is two-edged sword, as we all know. We need to have it to function adequately in our life and HIIT is a great way of getting a good dose of that in a good amount in a healthy human being. But in an unhealthy overstressed human being, which unfortunately, as you know, many people are becoming in today's world, I guess it can put you over the edge.


    I've seen this myself where just athletes are just training too hard too often, too much HIIT. Yeah, they get that downward spiral which becomes manifest into the overtraining syndrome. HIIT in its regular dose with adequate recovery is absolutely fantastic for some of the reasons that I just mentioned. But too much and then, if you're in a stressed situation, then more the MAF training is probably going to get you out of that and then allow you to bring some of these HIIT training back in sort of smaller doses.

Christopher:    That is the trouble with podcast is you don't really know who you're talking to. If I was listening to this in 2011 then the 140 beats approach was absolutely what I needed at that time. I wasn't sleeping properly. I didn't know how to feed myself. I couldn't go for more than 40 minutes on the bike without consuming a Maltodextrin gel. I had all kinds of gut dysbiosis. I literally knew nothing.

    It was quite remarkable that I could continue to exercise and recover my health and I think that MAF approach was what helped me get to where I am today. But then the thing that's going to get you to the next place is not necessarily what got you there. Like I said--

Paul:    Absolutely. And so many people are in that situation or went through that same story and, yeah, same sort of approach into the low carb, into the LSD type training, and then once you're healthy again add the HIIT training and, boom, now you're bulletproof, right? Yeah.

Christopher:    Yeah. And to connect the dots for the listeners, you're not the first person to talk about the importance of the type two fast-twitch muscle fibers. Many guests have talked about including Tommy and Ken Ford and Joe Friel talked about it, his Fast After 50 book. I interviewed him many moons ago. The reason we think they're important is because those are the muscles that stabilize you in the event of a fall. You slip up in the bathtub. The fast-twitch fiber is gone and then you fall and break your hip in your latter years and that could be, and quite often is, fatal.

    It's not necessarily the fall that kills you but the hospital stay. So, hanging on to those fast-twitch fibers is very important. Actually, you're reminding me of a friend that I met via the podcast. He's an anesthesiologist in the UK. He puts his patients onto a stationary exercise bicycle and measures their VO2 max as a way of predicting the health outcome for an operation that they might be doing. If your VO2 max is below certain level, they may deem it too risky to do an operation and make over a different approach.

Paul:    We've highlighted two things that are really important if we're aging with health and longevity and it's interesting these are also super important for elite athletes too. But it's, one, maximal oxygen uptake and HIIT is going to give you that. Two, fast-twitch fiber recruitments or reminding those fast-twitch fibers they need to not diminish on us. But again, you want to make sure you're healthy first before you're targeting those responses and those stimuli.

Christopher:    When you wrote the book -- I haven't actually got the book yet. You have to tell us a little bit about the book. I've been doing your online video online training course which is actually better for me. I'm very much an audio visual learner and I've really been enjoying the training course, just listening, and I can speed you up a little bit, which I like. I'll speed you up to 1.5x and then I can get through it a bit quicker.

    I find it easier than reading a book. I'll get distracted or my mind tends to wander and then I realize I've just been moving my eyes over the last paragraph and I haven't actually been reading it. Whereas the video seems to keep me locked in much better.

Paul:    That's so funny.

Christopher:    Tell me about those two things. You wrote the book and you created the online video training course. Who were those medium for?

Paul:    That's a good question. Maybe just go back a little bit first to give the history of the book and the course. I guess, it started with -- So, Martin and I, my colleague Martin Buchheit, who is the co-author of the book and the co-author of the course, we wrote a literature review in the Journal of Sports Medicine in 2013. It became, in our world of academics, it became very popular.

    The publisher Human Kinetics came at us and they said, "Would you guys write the book based on this, please?" And we said no and they came back again and we've eventually got to a place where we said, "Okay. When I finish my Olympic cycle with New Zealand, In Rio, I'll move to Revelstoke and I'll write the book." That was what I went and did.

    I guess, initially, it was kind of written for practitioners and coaches that really want to understand more the science of high intensity interval training. Yeah, I guess, it has this little bit of hybrid to it where it's not just the science but also the application of that science because there's almost, we believe there's two worlds where there's this academic world that really gets into the nitty-gritty of the science that's out there which is, obviously, super important. That's how we learn.


    There's also a group of coaches that are out there, that they come at their experience from a different sort of way. It's not necessarily from the scientific background but the more the experiential learning which is equally important. Unfortunately, this again create sort of two worlds with the two not always talking well to one another. At least, that's in our experience.

    Hence, the purpose of this book is to sort of bridge that gap between both the science and the application. We expand on that two-part literature review and then we actually showed the application in 20 different sports. Those sports chapters are written by expert practitioners. They're actually embedded in some of the world's top sports. You name your sports and it's almost like the best person we've got there. They tell us actually how the science principles are actually applied in their context.

    For example, I did the triathlon chapter with my mate Dan Plews. We've got lots of experience in triathlon. Coaches would find that very interesting. We've got Mark Quod from Orica Greenedge cycling team. I forget what they are now but he writes the cycling chapter. And on and on it kind of goes. There's two sort of schools. Are you a coach and you want to understand a little bit more the science better so that you can refine your programming to get a better outcome or are you a scientist, even, and do you want to understand a little bit more how coaches think so that you can contribute a little bit more to, I guess, making your research in science a little bit more useful? Really that was the purpose. Whether or not we hit that, I'm not sure, but that was the overarching aim.

Christopher:    And did you think that there's any chance of the average person like me being able to read the book or do the training course and then design a program for our given sport? Or do you think it's too technical? I felt like I struggled a bit with chapter two, actually. I was going to tell you that one of the things I like the most about the training course is the fact that you bothered to do the quizzes.

    There's some books I've been reading lately that had been recommended to me by Josh Turknett who's our resident neurologist friend. There's some really great books. I've come to realize from reading those books that quiz, as much as you might hate them, is actually an important part of how we learn. The forced recall tells you whether or not you just learned something or not. You'll never know unless it was for the quiz.

    One thing I'd really like, and I know you don't really have control over this because you didn't necessarily implement the software that implements the training course, is if you could email me a week after I finished that unit and then get me to do the quiz. It's like just as I start to forget something and then you force me to recall what I've been learning, that really helps in solidifying stuff rather than when you've just watched the video. But I know that that's not something you necessarily have control over because you didn't write the software that implements the training.

Paul:    No. I mean, but we certainly have a say in that. That's something that I could definitely consider doing, Chris.

Christopher:    Tell me about it. Do you think the average person listening to this podcast would be able to implement a training program after doing the training course or reading the book or do you really need to hire a coach in order for this to happen?

Paul:    I think it really depends on the individual. So, if this is your passion, if your passion is writing programs, then this course is definitely for you because it's going to take you to the pretty high level. That's one of the other things I forgot to mention is that our course is also being integrated into certain university programs as well, almost at the second year level of sports science, for example. I guess, that's also t give you an idea where the level that it's pitched at.

    I mean, I think if you want to be a top level coach you should be striving for, I guess, understanding sports science and training programming at least the second year sports science level. I guess, it would totally depend o the individual. If you want to understand training then the course is 110% for you. But if science is not your thing, there might be different things, obviously, for you.

Christopher:    I don't think anyone listening to this will say that science is not their thing.

Paul:    No, exactly. I mean, your audience, I think, would really love it though. You've got a listening audience of learners. Yeah, I think it would be good for them.

Christopher:    I'll tell you what I did do. I'm doing the training course and I'm very much enjoying it but then I also hired a coach. The coach is Simon Marshall and Leslie Patterson, both of whom had been on the podcast more than once. I'm coaching with them over at Braveheart. I can tell you that almost every time I go out there's some component of interval training. I don't feel like I'm smashing it and over reaching too far but there's definitely a component of that every time.


    And the reason I'm doing that is because they've been able to diagnose something with a power test. They'd be looking at power files and then saying, "Oh, I can see this is where you're lacking and this is where we need to focus our attention." There's so many different sports that we could talk about. There's not really enough time to talk about them all. Let's focus on your area of expertise which is triathlon. How do you go about using high intensity interval training when you're training an elite triathlete?

Paul:    Yeah, sure. That's a great question. And all of the, again, all of the chapters within those sports sort of follow the same method where they go and describe the actual sport in the chapter, reverse engineer the principles to say, well, what actually matters in this sport and then sort of show you the key, what we call weapons or formats, HIIT formats that can be used to target the, I guess, the adaptations that you're after and the things that matter. Much with the same example that you just described with your coaches, Chris.

    In triathlon, we can -- We've got basically four different triathlon categories that we have out there. We've got our sprint, Olympic, half Ironman and Iron man distance triathlons. We need to actually, first of all, break those down and know what the target of performance is. Now, if we want to take the sprint distance triathlon, this is a relatively shorter duration higher intensity event. The target in that one is going to be a little bit more VO2 max top level critical power, critical speed anaerobic threshold type training.

    But then on the other end of the spectrum, if we go to the Ironman triathlon talking eight to nine hours type event for elite, well, now we're looking at something called the first ventilatory threshold or the aerobic threshold, the MAF level, as one target. And interestingly, only realize in the last couple of years, the second target is actually VO2 max.

    With those, based on the research that's showing that, we tend to program the traithletes, I guess, with sessions that are targeting both of those areas. What are the types of formats that are going to target VO2 max? Let's take -- I mean, my specialty is the Ironman triathlon and maybe, I'm imagining, there might be some of your listeners that are interested in that one.

    I coach a number of high profile guys including Kyle Buckingham and others. Let's go and take that program. In those types of programs, I want to be looking at a longer duration fatmax type session. For example, fasted sessions, fasted bike sessions up to six--

Christopher:    That's what you mean by fatmax?

Paul:    Yes. So, the maximal rate of fat oxidation that you can produce. You really want to be having the ability to oxidize fatty acids and ketones ultimately. That is analogous to what that first ventilatory threshold, your aerobic threshold. This is an intensity that will feel moderate to heavy kind of thing. You can do this intensity ideally all day. This would be your Ironman pace almost. If you're going to set out and do an Ironman, this should be the pace that you should be able to sustain.

    It's not what triathletes always go at. They often don't pace properly. But that's the intensity they should be going though. We want to up that level. Things like your fasted training sessions and for long durations tend to be ones that elicit the signals that allow those adaptations to occur for all different events, swim, bike and run.

    Now, back to the HIIT training, we now need other days in our program to target the top end that VO2 max. This is going to equally be a stimulus that's going to up that ceiling. So, now, what are some of the sessions that we can use to up our VO2 max work or up our VO2 max? Those we define as short intervals. Short intervals, they have work durations above your VO2 max power or speed between 100 and 120% of that power or speed.

    For durations that range, well, from ten seconds to 60 seconds, but just as a middle marker there, like a 30 on-30 off is a great session for eliciting your VO2 max. This one is quite sustainable. For example, yeah, you might do four sets of 30 on-30 off where you're doing, in each one of those sets, you might be doing from four to ten really, just to start easy, and then build the number of reps up. Yeah, we will eventually elicit VO2 max in those types of sessions. That's a great one.


    And then the other one is the classic VO2 max, long intervals. That would be another one that would target this one too. You might be doing two minutes on-two minutes off or three minutes on-three minutes off, four minutes on-four minute off, all that VO2 max power or speed. And these are going to be, in both of those cases, we're going to be getting heart rates that are towards maximal, at least above 90 to 95% of heart rate max.

    And you'll know these as well, like how these sessions feel, you'll really hear that heavy breathing. You know the cardiorespiratory system is maximal. You're getting all those adaptations at the cardiovascular level that we know are important, that maximal ventricular filling pressure and stroke volume. Of course, these sessions tend to be a little bit more strenuous, tend to be. Actually, it probably depends on what your strengths and weaknesses are.

    If your fat max is really low then something like a four to six-hour fasted session is probably going to be absolutely killer on you. That tends to be easier for the more experienced guys. So, generally, putting a program together that has a balance of both of those almost as we spoke about before with, when we started the conversation with the MAF stuff.

Christopher:    Right. Can you just make that clear? So, you're doing fasted state sessions with your athletes, that is maybe sending them out on Saturday morning -- I guess, if your guys are not working then this is what they do, right? This is their day job. They could go out any day. But you're sending them out before they have breakfast. They've had an overnight fast and then they do a longer less intense session where the goal is to maximize fat oxidation. Am I right in thinking that?

Paul:    Yeah, perfect. Exactly.

Christopher:    Okay. So, the high intensity interval training, where does it fit in at the macro level? Do you start doing that with your athletes right from the get go? Let's say they've come off a long rest period of several weeks, they're now beginning training for the next race season. Would you use high intensity interval training from the outset or this just comes later on as they get closer towards racing?

Paul:    Yeah, man, that is a good question. I get asked so many times. Yeah, the answer is yes. With maybe a single week of just train to train, so to speak, and get with the aerobic math sort of stuff, if there's been a prolonged time off. But almost, if they're experienced, almost right into it in week one. But, I should say, with a low dose of it. Think about yourself. Right now, even if you're not that well trained, you know yourself you can do two or three reps, right, of a high intensity interval session.

    Back the HIIT session up to the level that is manageable for yourself but do something, like dig in at least as a starting point to those larger motor units and having some level of higher heart rate, for example. Absolutely right off the bat in moderation and then follow that day up with some recovery and more aerobic training. But absolutely right from the get go, just about, within some level of common sense. But, yeah, pretty much for us, day dot one.

Christopher:    Talk about how you measure intensity during these work periods. Because there's a few different ways that we could do it. Which are the best ways and how do you do it?

Paul:    I would measure my intensity in a triathlon context just through the classic means of your GPS, your power meter for the external training load variables and then our internal training load variable would be the heart rate. That's really all we have. I should also mention we can use a session RPE as well. That's a feature that I've noticed recently has come up on TrainingPeaks which is really useful.

Christopher:    So, rate of perceived exertion.

Paul:    Yeah, how does that session feel overall after -- How would you rate that session? How hard was that session? That's a great little internal training load marker. We cover that in detail in both chapters eight and chapter nine of our textbook and course. You'll see that one coming in in terms of judging -- That would be considered an internal training load marker. Internal because it's really the brain's sensor of what's going on.

    We have to really trust our athletes in terms of what sort of stress that had on us. Session RPE is absolutely fantastic because it incorporates other factors that you really can't get that well from just either heart rate or power or speed and other stressors such as your heat or your altitude. These sorts of things can be all sort of encompassing within that session RPE. The brain does a good job of knowing how stress, the type of stress that it was under in that particular session.

Christopher:    Descriptive though. If I'm coaching with you and I look in my TrainingPeaks or whatever it is for today, how will you prescribe the work periods?

Paul:    That's another good one. Again, I see mixed methods throughout there. For me, I set a number of various zones, as many coaches do. I use a five-zone model pretty much, classic five-zone model. The five-zone model is good because it links in well with those thresholds that I mentioned before. The aerobic threshold would be almost like your zone one and your zone two.


    Your anaerobic threshold kind of goes to the next level, between three and four. It sort of hits the bottom level of four. And then above the anaerobic threshold is your four or your zone five. I guess, I break those zones down and that's the -- If I was going to ask for a session, so it might be, say, a bike session and it's going to be three hours of riding at zone two, and we might have some modern intensity exercise that's in the moderate zone training. And this might be like an Ironman type stimulus.

    We'd be asking for a zone three level for those types of effort. I'd actually describe them as either 70.3 or Ironman sort of pace. Again, it's very feel based. But with the athlete knowing where either the speed, power and heart rate tend to approximate. Again, I'm a big believer that the brain knows where those are at. It's prescribed first by feel monitor and see sort of what came of that session. You can really tell quite nicely when an athlete is, I guess, almost maybe inappropriately pacing because the heart rate will tend to rise in those sessions.

    Whereas at least in an experienced athlete, they just lock straight in. My experienced guys, with the knowledge that when they're asked to do those various different sessions at those various given paces, they lock straight into both the power and the speed and the heart rate and they just don't drift, if you know what I mean.

    They'll drift if they're prescribed at a level that's above, like into the level four is kind of thing which it should, but anything that's below that level two or level three type prescription at 70.3 or an Ironman type pace, they just lock straight into that based on their experience. Does that answer your question?

Christopher:    It does, yes. I guess, the problem though with heart rate is it's a lacking indicator. If you've just prescribed a bunch of 30 seconds on-30 seconds off intervals, then the heart rate is not going to be of any use for judging intensity of the work period.

Paul:    Right. Very good point. And you're spot on. That's one of the biggest limitations of any of the monitoring tools, internal monitoring tools that we have, is that we can't really get an insight into what's happening above your threshold due to that sort of drift. Again, it's good to monitor it, see where heart rate is going, but we're really not getting any insight into what's happening with those, the recruitment of those fast-twitch fibers.

    That's when we need to be using our GPS watches for running speed, for example, and our power meters for the powers that are achieved, say, for example, in those 30 seconds on-30 seconds off. We're we actually at 120% of likely VO2 max power, for example? Yeah. And then, again, with the feel based, if again the athlete knows that those feel like and then it's quite rewarding when, lo and behold, adaptation takes place and we can just five-watt increase from the last session or a drop in kilometers per minute or whatever.

Christopher:    At the risk of going off on a tangent, do you ever notice that sometimes all of these gadgets can maybe remove your innate intelligence and perhaps become a bit of a drag? When I first got back into formal coaching with Leslie and Simon, as fantastic work as I think they do, god, did I ever like drag my heels over Bluetooth? I really hate Bluetooth. Messing around with those little coin cells to try to make a heart rate monitor work.

    And then I've got a Stages power meter which is pretty good for the price but, my god, the coin cells just drive me bonkers. I'm like waiting for things to get the GPS locked and then for all the Bluetooth devices to pair and then, oh, it doesn't work so now I have to check all the coin cells and, oh, there's a software update for my power meter, fantastic, and then you're 45 minutes into the allotted time for your ride and realize you haven't actually done anything yet. Is that just me being particular?

Paul:    No. Everyone experiences that. That's why equipment selection is really, really key, at least at the pointy end of this sort of stuff. When you really want to know and it's all -- A lot of this stuff is really important for confidence as well, at least at the elite level. And probably everyone too. But again, if you're high end you might want to be selecting Stages. Sorry, Stages, but yeah, again, I have the same problems. I'm just switching those things. I've used that one so. Might want a higher end model, some of the SRM and equivalent et cetera where you're just not seeing those same sort of problems or bulletproof for a lot longer.

Christopher:    That's interesting.

Paul:    They certainly will. All equipment will fail but, yeah, in my experience, you tend to get a little bit more -- You get what you pay for type thing.


Christopher:    Okay. That's interesting because SRM were really the dominant player when Stages came onto the scene. I guess they intended to disrupt what -- They just had almost a monopoly with a very expensive device and the Stages meter was just so much cheaper which was the only reason I entertained buying a power meter for my mountain bike. I now have a few of them. They're old. So, for all I know, Stages have sorted out all of the problems that I'm experiencing on a daily basis and I just need to put my hand back in my pocket and buy a new one. But that is what you're seeing then even with the latest Stages devices, the SRM is still the king of that market.

Paul:    Yeah. I mean, I would also say SRM -- The patents expired with SRM so there's a number of other players that are out there that are using really the same sort of thing. I think Quarq is one and I think there's others.

Christopher:    Of course, Quarq, yeah. I have those too.

Paul:    Again, in my experience, those ones tend to be a little bit more solid. But, yeah, I mean, everything's got its challenges and it's probably luck in the draw too. You might get it done every once in a while. But, yeah, those tend to be pretty good from the guys that I'm working with and I'm using and it's pretty consistent and reliable data that's coming in. Again, for those that aren't aware, just these automated uploads that often through Garmin Connect or whatnot. As soon as they're in the door it's just automatically being uploaded straight to me.

    We have a good system that's going on. But every once in a while, an athlete will just say, "I'm not sure what happened. My heart monitor or my power meter, seems something's going on. So, I got to get it worked on." Yeah, it's a little bit annoying and you just have to trust that the athlete knows by that time what's going on and the session is going well.

Christopher:    You're making me laugh because you're reminding me of the old post bike routine which is you get in the door and you knock your children out of the way to get to the refrigerator and then once you've been in the fridge you go over to your laptop so that you can upload your data whilst you're eating whatever you recovered from the refrigerator. I'm joking. Don't do that anymore. Promise.

Paul:    No. Exactly. Because you're fat-adapted so you're a lot more in control of your emotions. You're not hangry anymore. That's right.

Christopher:    Tell me about the importance of carrying out the session exactly as prescribed. This is something that causes me quite a lot of stress as well. When you see someone give -- I mean, you have to quantify. Unless you want to say, oh, this is a fartlek workout, and maybe you can talk about that. But when you say 30 seconds on-30 seconds off, maybe that's easy to do as a triathlete on the road. And I bet there are some places where it's still quite difficult to do that as a triathlete on the road because as soon as the road goes downhill, it's really hard to hit, say, I don't know how many watts you're getting. To pedal really hard downhill I think is quite tricky no matter what.

    As a mountain biker, it becomes even more challenging. The thing that's dictating my power output is not so much what you wrote in my TrainingPeaks but what I see on the trail in front of me, right? So, how important is it then that you implement these workouts exactly as prescribed?

Paul:    I mean, you can get away with one or two not being perfect but maybe it's just the type of people that are attracted--

Christopher:    Let me ask you a different question. Has anyone ever done that experiment? Say, fartlek, which is -- Let me ask you what is fartlek so that I don't mess up the definition.

Paul:    It's a Swedish term meaning speed play and it's basically random high intensity interval training. It's like, I think I'm going to feel like I'm going to go hard now so go hard. And you're usually doing this with a group and people are chasing you kind of thing and it's just you're having a little bit of fun with high intensity interval training. But just as you feel.

Christopher:    Right. And this lends itself very well to mountain biking because, "Oh, look, there's a difficult uphill technical section here. Let's smash it to get over this." And then the other side of that, there'll be a rest period. Has anyone ever done a study like that where they've compared something like fartlek to a more rigid quantified strategy like the 30-seconds on-30 seconds off?

Paul:    Yeah. It's a really good point. I think stretching my memory at the moment, I'm not sure if there's an actual formal study. There may have been. And probably someone is going to email me after this and remind me of the study that was done, which is cool. Please do.

Christopher:    And if you think there's something -- So, we make really comprehensive show notes now. I say we. I mean, Elaine makes really comprehensive show notes now. She does a fantastic job. Everything that we've mentioned during this interview will be linked in the show notes. If you think of a study later on, we can absolutely link that later.

Paul:    I guess, what I'm thinking on that is the problem with the fartlek session is it's almost like it would be -- It's an awesome one to do in that early sort of stage, almost would recommend that one. Remember we went back and said do you do this early on in the piece in terms of when you're just starting back into training? Maybe after your off season?


    This will be the perfect one to kind of do at that certain stage, just start digging into the higher intensity sort of bandwidths. But as you get along to -- You're dealing with a 20 plus hour training week, at least to triathletes that's a higher level, in my opinion, you want to be a little bit more precise with your targeting. The HIIT sessions prescribed when they're short intervals, long intervals, you're trying to get certain time at VO2 max.

    Remember, again, we were talking about that VO2 max and the importance of that one. Well, the length of time that you can actually achieve at that VO2 max is one of the factors that many feel is actually important. I guess, eliciting the ultimate sort of performance, ultimate raise of your VO2 max and in turn capacity to perform. You might not be as precise with a feel based sort of method in targeting that. You may but you're taking a chance, I guess. With my type A type athletes, they're pretty precise and rarely missing an interval even.

Christopher:    Yeah. Let me ask you this. How many of those athletes perform the workouts on a stationary bicycle indoors? And in particular, indoors when they could be outdoors? I realize that for some people it's just not possible to ride outdoors because it's icy or dangerous for some reason. But are there any guys out there and girls that are using the stationary bicycle just so that they can implement these sessions correctly when they could be outdoors riding their bike?

Paul:    Absolutely. I feel like that the indoor stationary trainer and the stationary trainer is just a tool that either the cyclist or the triathlete needs to have at their disposal for that exact reason. It just, again, allows for the precise targeting of those high intensity sessions especially the ability to do these sessions when the weather is poor. Yeah, you just, for various different reasons. Sometimes also you have shorter sessions that you just want to hit the high intensity sort of stimulus. It's maybe only an hour or an hour and a half and that might be a great -- It might just be a lot easier to jump on your trainer and hit those targets and then walk to the next session or into recovery.

    I also forgot to answer your question as well with respect to the undulating terrain for a cyclist. It tends to help to actually find a gradient, a decent gradient and actually perform like a 30 on-30 off on that on that hill. It's just a lot easier to get the power and to have the power be consistent. Because the power output kinetics or dynamics, they alter when you're going downhill. As you know, right, all of a sudden you're spinning out kind of thing and you just can't really--

Christopher:    You can still get rounded by dragging your brake. That always makes me cringe.

Paul:    No. That would be just kind of ridiculous. Yeah, you need to know your surroundings, know your own context, what are going to be some good areas in your neighborhood that you can get this high intensity session in outdoors. If you're a city dweller, well, then trainer is probably definitely going to be the thing that you're going to want to have. But if you are living out in the sticks a little bit more then, yeah, know your terrain and know the different spots to be able to do some of these sorts of HIIT workouts and do the HIIT phase, the workouts on the uphill.

Christopher:    I think what it is, the reason I'm hung up on this, as you can probably tell that I have quite a lot of ambivalence over what is it I want? Do I want to perform at the highest level or do I just want to go out and ride my bike and have fun? Both of those things are valid pursuits and at the moment I'm sort of torn between the two. And I see the stationary bicycle, I think I gave it to a friend five years ago, and it was almost like letting go to cigarettes. It was one of the things that I was using to self-medicate was exercise. I didn't feel very good. But I've always felt a bit better after I exercise.

    And so the stationary bicycle was an important tool that I could take anywhere. You can just whip out and self-medicate for 60 minutes or maybe even 30 minutes so you'd feel so much better. And letting that go was kind of an important milestone in my progression as a human. But now I realize that maybe I have to bring it back for the performance component.

Paul:    Totally. Well, I mean, it's just the right tool at the right time. Yeah, you don't want to do all your sessions on that but once or twice a week, it can be very beneficial to just hit those signals that you're after if you're not getting those on the road or in the trails for certain reason depending on your context.

Christopher:    One of the things I wondered about and I wondered if there's anything in the book about this, I certainly haven't encountered it in the training course yet, and that is the behavioral science of high intensity interval training. For some people, I think, myself included, it's not always easy to go out and do a really hard workout just because that's what it says on the calendar.


    If you were to ask me to go do a bike race at that time or a hard group ride or something you'll probably find I have no trouble whatsoever. But just going hard for the sake of going hard or going hard for the sake of what it says in your calendar is really quite difficult. And so is that just something, a personal problem for me yet again, right? And so the people at the highest level are really not having this trouble. They can just go out and smash it on demand assuming that you're not over reaching or over training them too hard. Or does everyone have this problem? How do I motivate this thing? How do I get this going? Does everyone have that problem?

Paul:    I think everyone does, right?

Christopher:    I'll tell you what, I've got this monkey on my back. There's a really good book called Chimp Paradox. Steve Peters, I think, is the name of the author.

Paul:    I always recommend the book.

Christopher:    Yeah, it's a good book. And so you've got this monkey on your back that's screaming. It's telling you some version of the you're not good enough story. What is point of this? You're not going to get any faster? Nobody cares about the results, anyway. What are you doing? This is hurting me. Slow down. So, you've got this monkey on your back that's screaming at you like this and then the only thing you've got on the other side of that equation is, "But that's what Paul put in my TrainingPeaks so I must go at 500 watts for 30 seconds just as he prescribed."

Paul:    Yeah. I guess, where I was going to go with this was, it's mainly the observations of one of my athletes, Scott. He's this really great up and coming age group triathlete and I enjoy reading his comments on TrainingPeaks. He gets into these sessions. He's a 20 plus hour trainer. He's a four-hour half Ironman guy and he'll be doing these sorts of sessions and he'll feel like he just did not think he could get up for these sessions but he always gives it a try. And then, lo and behold, he always talks through on his TrainingPeaks comments and he says how he really warmed into it and then couldn't believe how his body just absolutely woke up and exploded into these on set two, three and four, for example.

    It's just a bit of, I guess, to go back to the original question, I think it's just, or original point, I think we all do sometimes experience these feelings based on our days and how it's unrolling and overall stress. But it's interesting how we become alive and the central nervous system becomes a little bit more activated. You'd be surprised at what the body is actually capable of and what the body actually enjoys even sometimes.

    The general rule of thumb for my athletes is that they at least always give the session a try. But if they're still feeling real crap after two and three, set two and three, they have the ability to pull the set and that's actually why I actually prescribed -- Very often I prescribe it as two to four 30 on-30 offs, a certain number of 30 on-30 offs. And they know that they're going to get an A plus from Paul if they do their four but they well and truly also are going to get an A plus if they pull at after just two because they know they're listening to their body, if that makes sense.

Christopher:    Okay. Yeah. I certainly have enjoyed that technique or found that technique to be useful where, okay, can you do one? All right. Let's see if we can do one. Or I can do one. Can you do another one? Yeah, I can do another one. And then that's how you do it. You don't think about, "Oh, I'm going to do eight of these." You think, can I do one? And then make another decision once you've done one.

Paul:    That is so the psychology of interval training. Absolutely, yeah, you shouldn't be thinking really about doing four sets of these. Just do the one. And then just do the next one. So, yeah, that is the psychology of HIIT training. But go out there and do one and see how that feels for you, the listener.

Christopher:    Let me ask you the most important question last, the question I realized I should have asked you at the beginning and that is how much better can you expect somebody to get through high intensity interval training? Can you give us -- I know there's nothing you can say in general terms but can you give us a story about a triathlete, say, who came to you and they did power test and you saw some numbers and then they did a coaching program with you that included high intensity interval training and then you repeated the test and then you saw better numbers. Is there a story like that that come to mind so you can give us a feel for what might be possible?

Paul:    Yeah, for sure. I'll give you two stories and they revolve around the science and application of high intensity interval training in my context. I started in this field in 2000 at the University of Queensland in Australia, did my PhD in the area. The key study that I did was in a group of 40 well trained cyclists. My overarching question was exactly as you put it. What is the effect of high intensity interval training on their performance?


    They were all coming in their off season. And we didn't really know as much at that time what the effect would be. And we did a variety of different sessions, VO2 max sessions, sprint interval training and we had a control group. Both the VO2 max training guys doing VO2 max type HIIT workouts as well as the sprint interval training workout guys well and truly beat out the individuals that are just doing sort of their MAF kind of training and going about their training week by upward of seven, 3% to 7% . So, 7% on the VO2 max group.

    That was measured over a 40-kilometer time trial in the laboratory. Everything sort of, I guess, rose from there for me in terms of my understanding and, hence, today with the book. Now, let's go to the application of that. In comes Kyle Buckingham who's a world top ten Ironman triahtlete that I worked with. When he came to me first, he had, I guess, not a lot of VO2 max type intervals in his program. Yeah, high intensity interval training per se.

    A lot of the moderate intensity stuff that's very important for specifically targeting Ironman performance, but he lacked that, I guess, that top end VO2 max type sort of training. Same sort of story. We applied this and, yeah, he, I guess, listed an outstanding performance. He won Ironman South Africa last year and, yeah, a number of other top ten results. Yeah, just, I guess, both the science based, definitely know it works, working with Kyle and others definitely know it works.

    It's often a piece of the puzzle, the training program puzzle that is missing and that's the reason why, I guess, the importance of understanding it as either a coach or, of course, an athlete if you care about your performance. Plug for my book and course in that context.

Christopher:    Yeah, absolutely. I think of this is a trap that a lot of older athletes fall into. And the reason I think that is from reading Joe Friel's book. As people get older, it's the high intensity component that tends to fall away from activity. It's enormously tempting for me. It's just too good to be true, the MAF thing, the 140 beats things. It's too good to be true. You mean, I can just go grab the dogs right now and ride my mountain bike in the woods for 90 minutes without having my heart rate go over 140 and get faster? It's like having my cake and eating it. It's just too good to be true. And I think it is too good to be true.

Paul:    It is. I mean, it has its place. It's an important piece as well but there's a lot of different pieces of the puzzle and HIIT is one of the very important ones.

Christopher:    Right. It's not an either-or.

Paul:    No, definitely not. You need to have the full blend of all of them.

Christopher:    Well, the name of the training course that I've been doing -- I'm 21% through it although I know I need to go back to chapter two because I flunked the exam pretty badly. I did really well on the chapter one quiz but chapter two, not so much. I know I need to go back and do that again. The name of the training course is Science and Application of High Intensity Interval Training. I will, of course, link to that in the show notes. Does the book got the same title?

Paul:    Yes, it does, for sure. And, yeah, our website is HIITscience, which I'm sure you'll link too. You can get the book or the course from that site.

Christopher:    I also realized that I didn't mention the name of the book that I've been reading that Josh Turknett recommended. It was Make it Stick: The Science of Successful Learning by Peter Brown. Obviously, it's not working because I didn't remember the name of the book to mention it when I mentioned it in the first place. It's really good. That's the kind of -- I would have cringed at the quizzes a little bit before I read that book and then I realized that they were really important tools. It's really nice to see those things coming together.

    One last question for you. If I don't want to try and figure out this out by myself and I want a coach, how do you go about finding a coach? Do you have room to coach some additional athletes? Or, if not, where can people find a coach that's done your training course, read your book, is up to speed on your science so that they can apply some of these techniques in a training program?

Paul:    Unfortunately, I am too full at the moment personally.

Christopher:     I knew you were going to say that.

Paul:    Yeah. There's so many -- Yeah, we get asked so much and it's really -- This is one of the goals that we're -- If I can just actually throw a plug in here. If there's anyone out there that is an investor or knows people that are investors, this is our next phase where we want to get little bit more into actually creating, I guess, accredited HIIT science instructors. So, people that have actually, coaches that have actually taken the course and actually understand these sorts of principles.

    And then the other one is the integration with technology as well. Actually, creating tools that actually make the prescription of this a little bit easier and actually having dynamic plans based on the IP that's within the HIIT science, I guess, philosophy that you can read about there.


    If there are, yeah, investors or links to investors out there, we'd love to hear from you. We are currently seeking those at the moment to try to fill that void that you just identified, Chris.

Christopher:    Well, that's fantastic. That's exciting. It sounds like we should stay tuned and I'll need to invite you back. I hope it won't be another two years before you come back and talk to us again. There's so much more that we could go into like heart variability also. Is there anything you want to say about that quite quickly?

Paul:    I mean, chapter nine deals with heart rate variability completely.

Christopher:    Oh, it does. That's great.

Paul:    You're coming to that. You're going to become an expert if you continue on, Chris.

Christopher:    Okay. That's exciting.

Paul:    Yeah. Chapter eight and chapter nine are really phenomenal. Again, kudos to Martin Buchheit for leading that, the initiatives throughout those ones. That's basically looking at the load, actually quantifying the load of training, and then looking at the response, the individual response to load. And that really comes down to the heart rate variability assessment. That's all in there. Yeah, again, that's a whole other podcast, of course, as you know.

Christopher:    I feel bad that we didn't really give Martin much credit but it's a joint effort for the two of you, the book and the--

Paul:    We call him the man with three brains, really. He is an absolute genius. He is, I don't know if you know, football or soccer, but there's a team in Europe called Paris Saint-Germain Football Club and it's one of the premier leagues. He's the head of performance for Paris Saint-Germain. He does HIIT science in his spare time. The man just does not sleep. I worry about the fella's health but he is an absolute genius and we're so blessed to have him leading this initiative with HIIT science and thanks for being to pause there and just, I guess, give full credit to Martin.

Christopher:    He's heavy thick accent kind of maybe trip up in the beginning and then I realized, again, that this might be an important part of my learning because it forced me to slow down and really pay attention to what he was saying.

Paul:    I got to say, one of the things you said, people say they always speed me up at 1.5 and then they slow down to 0.5 with Martin.

Christopher:    And I think that's what it is. It's important. This is also in the Science of Making it Stick. They've done experiments where they try and teach people using a ridiculous font like Comic Sans or something and it forces people to slow down and pay very close attention to what's being said. And maybe Martin is actually--

Paul:    That's good because there's some genius in those words so it's a really good thing to do.

Christopher:    Yeah, fantastic. So, the Science and Application of High Intensity Interval Training is the name of the training course and the book. Is there anywhere else you'd want to send people online that I should link in the show notes, Paul?

Paul:    It's HIITscience and we're on all the socials, So, just check us out there and, yeah, there's loads of free stuff too. If you actually click through the learn more and sign in there, there's I think about five lessons that are actually free now. You can actually get a feel for it. Go through that and please provide us your feedback. We'll continue to try to make it better.

Christopher:    That's fantastic. Well, thank you so much for your time, Paul. I really appreciate you.

Paul:    I appreciate the platform to expose everything we're doing. Thanks so much, Chris.

Christopher:    Thank you.


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