#293 - AMA #57： High-intensity interval training： benefits, risks, protocols, and impact on longevity
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Summary
In this episode of the Ask Me Anything podcast, we cover the topic of High Intensity Interval Training (HIIT) and how it relates to longevity. We cover what exactly is it, when is it beneficial, and when it's not, as well as the best protocol to use for HIIT. We also discuss the importance of broadening your portfolio of exercise training, and how to increase your VO2 max.
Transcript
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Hey everyone, welcome to a sneak peek, ask me anything or AMA episode of the drive podcast.
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I'm your host, Peter Atiyah. At the end of this short episode, I'll explain how you can
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access the AMA episodes in full, along with a ton of other membership benefits we've created,
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or you can learn more now by going to peteratiyahmd.com forward slash subscribe. So without
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further delay, here's today's sneak peek of the ask me anything episode.
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Welcome to ask me anything episode 57. I'm once again joined by my co-host Nick Stenson.
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In today's episode, we dive deep into the topic of HIT, high intensity interval training. This is a
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topic we get asked about a lot, and it seems that there is a lot of confusion around both the
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semantics of this and perhaps more importantly, the data. So in today's AMA, we cover what exactly
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HIT is and what the different types are. When is HIT beneficial and when is it not, especially if
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you're looking through the lens of longevity, the importance of broadening your portfolio of exercise
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training, and we talk about the best protocol if you're going to use HIT. Throughout this conversation,
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we also speak about VO2 max and what a person can do to increase their VO2 max, which is something
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we know is a very important metric for longevity. And of course, how does HIT training factor into
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that? If you're a subscriber and you want to watch the full video of the podcast, you can find it on
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the show notes page. And if you're not a subscriber, you can watch a sneak peek of the video on our
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YouTube page. So without further delay, I hope you enjoy AMA number 57.
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Peter, welcome to another AMA. How are you doing?
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Awesome. Well, today's episode is going to be exercise related, but kind of on a topic that we
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get asked about a lot and we haven't really covered, which is HIT or high intensity interval training.
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And it's something that people see everywhere. It's marketed a lot. People talk about it. And so
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we see a lot of questions come through around people who are wondering more about it. What are
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the different types? How does interval training fit in? Where can it be used? Where is it limited?
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What's the quote unquote best protocol? And I think we gathered a lot of those questions,
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which we'll cover today. And through it, I think we'll also hopefully talk a lot about how someone
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can increase their VO two max as well, which is something that we've talked a lot about the
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importance of VO two max. And a lot of people who are thinking about their longevity, it's something
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that they'll want to increase. So we'll hit on that. And then also no surprise to people. We'll also,
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I'm sure talk about the importance of having a broad exercise program and training, and not just
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specifically focusing on one thing. So we have a lot to do with that said, anything you want to add
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before we hit the first question? No pun intended. I think that's great. I think there's a lot to
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cover here. This was a subject matter that we had been kicking down the road a little bit because
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we couldn't wrap our head around the right way to present it. And I feel like it really kind of came
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together in the last couple of weeks. I feel much better about this subject matter. So I'm glad we waited
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until we had the data that we've got, the studies that we've been able to look at. And then obviously
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the implications so that we make this much more rooted in what do you need to do as opposed to
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making sure you understand every molecular pathway of hit. Yeah, I think that's correct. And I think
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it would help to start off with just talking about the word hit because hit is such a commonly used
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word when people talk about exercise. Can you maybe set the stage of where it even comes from?
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Yeah, this is something I was kind of curious to learn about as we were getting ready to prep for
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this because I learned a little bit of this stuff when I was writing Outlive and it actually didn't
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make the final cut in the spirit of half the stuff you end up writing in the first draft is on the
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cutting room floor. So it was kind of fun to go back to some of this stuff. But this stuff gets
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documented as far back as the 1800s, which in some ways seems like a long time ago, in some ways is
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not obviously, but given the relative paucity of time that we have serious training, I would say
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that this is a long time. And basically what it comes down to is some documentation of athletes
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having altered their tempo between running and walking for their training. But it wouldn't really
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be until kind of the early 1900s that it would be codified more seriously. You would originally go back
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to kind of the Finnish Olympic runners that first employed this type of training. And anyone who's
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done any running or interval training might be familiar with the term fartlek, F-A-R-T-L-E-K,
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which I believe was coined in the 1930s. It comes or is derived from the Swedish language. And I think
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it refers to playing or speed play or something like that. So when I was actually growing up, we referred
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to it as speed play. So alternating fast and slow. I would suspect that a bunch of people listening to
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us are probably familiar with a type of interval known as Tabata training. So a Tabata interval is a
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very specific type of interval. This was first described in the 1990s, where a guy by the name
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of Tabata was the first author on a paper that first presented this. I think it was in the mid-90s.
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Interestingly though, the protocol seems to have been developed by a guy named Irsawa. And the
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interval was eight sets of 20 seconds on a bike all out interval with 10 seconds of rest. So you're
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20 seconds on, 10 seconds off, eight times, which gives you a four minute duration. And anyway, so I
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didn't learn about a Tabata probably until 10 years later when it was something that one of my cycling
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coaches employed many, many years later. So that's kind of the, the very, very short abbreviated version
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of how these interval trainings have come along. Another follow-up to that is there seems to be a
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lot of different programs, classes, gyms that call themselves hit training. And we see a lot of
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questions from people who are confused by this. And so I think it'd be helpful is, can you speak a
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little bit about what hit training actually is? And is there a way for people listening or watching
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to be able to differentiate between the different types of forms that they may see out there?
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Yeah. Hit definitely has a bit of a brand issue. By the way, when we're saying hit, I should clarify
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it's H-I-I-T. So high intensity interval training. And I think part of the problem with everything we're
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about to discuss today, at least a big part of it stems from the fact that there's no uniform
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definition in what constitutes hit. Now, what I'm going to try to suggest today is that we be a little
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bit more specific and we differentiate between, for example, high intensity interval training or hit
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versus sprint interval training or sit or things like Tabata training, which kind of are a bit of a
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subset of sit. The reason for that is they produce very different metabolic effects. They're obviously
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carried out at very different intensities. And by extension, they have some sort of different pros
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and cons. So given that the majority of the literature is on what is called hit, we're going
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to kind of start with that. But again, if you remember nothing else from this podcast, remember
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that when someone is talking to you about hit, ask them to stop using the language and just be
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specific, which is what is the effort level? What is the duration of work? What is the duration of
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rest? How often do I repeat it? How many times do I do it? It's really getting specific. That's going
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to be relevant. And obviously that's what we want to cover today. Nevertheless, hits are typically defined
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as sub-maximal efforts. So sub-maximal would be generally 80 to 95% of a person's maximum heart rate.
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But I will just tell you right now out of the gate, I think that definition is not that helpful.
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Because for example, when I do my zone two, I'm doing it at 80% of my max heart rate, not because
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I'm targeting that, but because that's the heart rate I end up being at when I'm in zone two. Well,
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that's clearly far from sub-maximal. And conversely, 95% of max heart rate is truly a huge effort.
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These efforts cover very different energy systems. But again, the purpose of hit is generally
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to put you in your maximum aerobic training zone, but clearly the duration of the interval
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and clearly the intensity will speak to how much anaerobic training you're getting in there
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as well. We'll unpack this a lot more, but let me just move on and now talk about sprint interval
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training. So sprint interval training in some ways I think is easier to understand because it is
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supra maximal. So these are efforts that would exceed the output of your VO2 max. So again,
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if we think about what VO2 max is, VO2 max is the maximal consumption of oxygen. So this is typically
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performed at a very high level, but not a peak level. So an all out 30 second sprint does not
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produce maximal O2 uptake. It's typically going to need to be a duration that's longer than that
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so let's just assume you've achieved the level of VO2 peak or VO2 max. You would then say, well,
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what was my power at that level or what was my speed at that level? And then sprint interval training
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is done at an effort that exceeds that. So it's a higher power or a higher speed. Now here's what's
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interesting. It's not necessarily a higher heart rate. And the reason for that is that if you imagine
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what your heart rate is doing at a VO2 max, you've taken a while to get up to that speed or that power,
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whatever it is you're using, and you're holding it for a couple of minutes, it really gives your
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heart rate a chance to peak. So when I'm doing VO2 max intervals on the bike, which I'm only doing
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once a week, I'm almost hitting max heart rate by the end. I'm probably within five beats of max
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heart rate. That's actually a higher heart rate than if I'm doing 20 second all outs on a Tabata
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because in that short period of time, and again, the sprint interval protocols are typically 10
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second, 20 second all outs. In fact, I think they're defined as up to 60 seconds, but you can't do
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anything all out at nearly that duration. You typically don't get your heart rate as high. And so
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they're typically done pegged to a power level or a speed level that is in excess of your peak VO2 max.
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Hopefully that kind of provides the right amount of clarity on maybe some of the distinction between
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hit and sit. Yeah. And I think we'll get to, like you said, a lot of the other stuff on the details
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with the later upcoming questions. Maybe one other thing I want to say, Nick, though,
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do you remember when I had Alex Hutchinson on the podcast two years ago, three years ago now,
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there's something very interesting that Alex Hutchinson wrote about in his book Endure,
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which is around the science of endurance. And I find this to be completely true for me,
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which is the only effort in which you can truly go all out is an effort up to about 10 seconds.
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And that might sound crazy because I'm sure there are people listening to this. You say,
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what are you talking about, man? I do 60 second all out bursts. I do 20 second all out bursts,
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30 second all out bursts. I don't think you do. I think if you're doing anything over 10 seconds,
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you are consciously or subconsciously applying some governor to that activity that keeps you from
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absolutely blowing up. And I know this, Alex goes through the science of this, but I can just tell
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you personally that there's a very big difference in how hard I'm able to push when I do a 10 second
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on 20 second off repeat versus a 20 second on 20 second off or 20 second on 10 second off repeat.
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And I'm very attentive to how much am I pushing without a limit and anything above 10 seconds,
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I seem to be just holding back slightly. So keep that in the back of your mind. When people talk about
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the term all out, that's a very misleading term. Real quick. You want to know a fun fact about the
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Alex Hutchinson podcast? Sure. It was the very first podcast we've ever done on video outside of
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one or two random ones before, but when we made the switch to video, Alex was the first person that
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we did that with. Very interesting. Another thing real quick, before we move on, you mentioned max
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heart rate. So I think kind of how you defined all out was really good. Can you let people know how
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they would know their max heart rate as well? Because I think it is going to be a metric that
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if anyone's kind of looking at this, they're going to want to know to really fully understand how this
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works. Yeah. Max heart rate is a pretty literal term. It's the maximum achieved heart rate. Now
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there are different ways to predict it. The most simple formula that is generally used is the 220
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minus your age formula. So if you're 50, your maximum heart rate would be expected to be 170 beats per
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minute, but a lot of factors play into it. And I don't think that the formula is sufficient.
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And therefore, I think the only way to really know it is to actually push yourself in sub-maximal
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efforts until you get to maximum heart rate. So this will typically be seen if a person does a VO2 max
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test and certainly will be seen if a person does a stress test if they're pushed to failure. But
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nevertheless, it is a good heart rate to know if you want to base any of your training on heart rate.
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I don't personally pay attention to it because everything I'm doing is either based on RPE or
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watts. And I'm using the watts to drive the sort of training interval. But some people do use heart
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rate. I don't think there's anything wrong with that, but I don't think it's as robust, frankly,
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as speed or Mets or watts. Moving on, I think it'd be helpful to just maybe cover why we probably see
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so many questions about HIIT. And I think the reason is you often see it touted as like a more
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efficient way to exercise or a more effective way to exercise. So do you maybe want to talk about why
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people are out there kind of making that claim as it relates to HIIT?
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