Rhonda: And this kind of relates to something I was gonna ask you about, which is interval training for maybe elderly and maybe infirm, so people that are more sick, how they can incorporate interval training into their lifestyle.

And also then like contraindication. So you mentioned like maybe some people, is there some people that high intensity interval training is not good for and how would you know sort of all of those?

Dr. Gibala: Yeah, so and this, I always make the point here, I'm a PhD scientist, I read the literature, I'm not a medical doctor, I'm not a cardiologist.

I read work like that, I try and stay informed on it. And certainly for my book, I interviewed people like Dr. Paul Thompson, noted cardiologist who writes many of the guidelines around this very issue. But first point I always make is that interval training, as we've talked about a lot, comes in many different flavors.

So second point is that many more people than we initially think can perform and benefit from interval training. And there's just now, there's hundreds and hundreds of studies that have looked at interval training in individuals with cardiometabolic disease, cardiovascular disease, heart disease, type 2 diabetes, older individuals, people with metabolic syndrome.

And a lot of this is not new. You can find studies going back to the 70s and 80s, some of the pioneering work looking at interval training in individuals with heart disease. So the notion that people could, you know, individuals with cardiometabolic diseases could engage and benefit from interval training is certainly not new.

But there remains immense debate. And I think it's, we're all reading the same science. And some people, again, I'm talking about the field broadly, some want to see the science get to a certain level before they recommend changes, and where that level is, is different. So for example, high-intensity interval training, my read is, is much more ingrained in Europe and certainly in Scandinavian countries.

It's, you know, much of the pioneering work around high-intensity interval training in cardiovascular disease was done in Norway in the work of Ulrich Wissloff, and that goes back to the calculator that we talked about earlier. But there, I think it's much more generally accepted and integrated into cardiac rehab training, where I think in North America, it's not, right?

And so that's not necessarily good or bad. I think it's the experts, the cardiologists, the people who write the guidelines, looking at the evidence and saying, you know, some are more, like I say, there's different viewpoints on that. In terms of risk, and again, I'm not an MD or a cardiologist, but in, there's no doubt that more vigorous intensity exercise can transiently increase risk of an event during the exercise bout itself.

I think there's fairly strong evidence for that, and you know, in preparing for our interview, I was reading some of the latest guidelines, expert guidelines around that, making that point. You know, and especially in more deconditioned individuals, people might already have some silent underlying risk factors, and so we can't ignore that or downplay it or say that everyone can do interval training and it's fine, but the absolute risk still remains low when you look at events per hours engaged in actual exercise.

You know, both moderate and vigorous type effort, whether it's continuous or intermittent, the absolute rates remain relatively low, but statistically, there's definitely an increase in risk that's higher with vigorous exercise during the event itself. Now, of course, after the event, relative risk is much lower than individuals who would remain sedentary.

So, you know, I think the old adage of the greatest risk to your health is just remain sedentary is absolutely true, right? And so when I, it's a striking phrase that Dr. Thompson used when we interviewed him for the book was, you know, if your choice is between doing HIIT and doing nothing, do HIIT. If the choice is between HIIT and moderate and you're 60 and you've been pretty inactive, you might have some underlying factors and time is not a worry, do moderate or at least engage in some moderate as some preconditioning before you start with the more intense stuff.

And then on the, you know, who is absolutely contraindicated, you know, atrial fibrillation. There are some very clearly defined no-goes that if you have certain conditions that you shouldn't be engaging vigorous intensity. Exercise unstable angina would be another example.

Rhonda: Yeah. It sounds like a lot of the, I mean, things that you would talk to your cardiologist about, you would already have a cardiologist if you would know that you had that sort of disorder.

Dr. Gibala: The last point I would make is, you know, in talking to many physicians and cardiologists, you know, we think an exercise stress test sort of gives you that green light or red light to engage in exercise. And certainly in our studies, where individuals had elevated risk, people with type 2 diabetes and that, everyone does a 12 lead ECG stress test before they're recruited into the study.

But you know, I naively thought, okay, the person doing the stress test, the cardiologist reading it, is going to come back and say, green light, good to go in your study, red light, unable. What we found was a lot of yellow lights. Maybe, you know, this person might be contraindicated or there's a change here that might elevate risk.

And so of course we defer to safety. And so even those yellow lights, generally those individuals were not then recruited into the study, which is no doubt influencing outcomes. But I always wonder, I'm like, so are these people just going to sit around then and continue doing nothing? And is that in itself raising their risk?

So it's, you know, even, you know, the standard, you know, recommendation, see your doctor, get clearance before you change or engage in exercise, it's not always 100% guarantee one way or the other in terms of you may deal with a sudden adverse event. We might see it in a 20-year-old in my lab tomorrow. You can't absolutely rule out these things.

Rhonda: I think also mentioning the walkers, the interval walkers versus continuous walkers was really good because, you know, it also kind of highlights the fact that you don't have to go to your 80% max heart rate for interval training. And perhaps people that are older, people that might have some underlying conditions, people that are untrained and are starting later in life, great.

It's never too late to start. They can start by, you know, by doing, you know, intervals that are not necessarily all out or even submaximal, right? I mean, just going a little bit above what your steady state being able to talk normally sort of conversation is.

Dr. Gibala: And, you know, I don't think that, you know, my sense is that many of your listeners are already aware of this, but I think still for a lot of people or certainly the general public, they hear the word HIIT or interval training and they think, oh my goodness, it's this as hard as you can go, all out, breakneck pace, and that's not for me.

And I think that's a disservice. And again, hopefully this more encompassing term of interval training, it's just this idea of hills and valleys, right? And the other point to that is, I'm not name dropping here, but just, you know, many people have thought about this for a long time. I also interviewed for the book, Carl Foster, who has done a lot of work around this.

And when he first heard, you know, as a scientist in the 80s, that there was a group in Germany that was doing interval training in cardiac patients, he saw one of the scientists at a conference and he said, oh, how many people you killed this week with that crazy stuff? And he was relaying that story to a cardiac nurse when he got back to his institution.

And the nurse, he said, sort of tapped him on the cheek and said, oh, Carl, you're so silly. And she said, look at this patient in the parking lot who's coming for his cardiac rehab session. They already engaged in interval training because they have such low exercise capacity, they can't get to a continuous moderate pace.

So what they do is they innately interval train. They get out of their car, they take a few steps, they take a break. They take a few more steps, they take a break. It's a bit like climbers on Everest, right? And so, again, that's a more empowering message, I think. You're just starting out, that's okay. You can train like elite athletes have trained.

We just have to set the workout at an approximate level that's suitable for you, rather than, you know, oh my goodness, people are destined to be a failure because very few can engage in continuous moderate exercise for a period of even 20 or 30 minutes because their capacities are so low. So it's a bit of, you know, the behavioral colleagues talk about message framing.

I think there's a lot of that we can do with interval training. So for those individuals who just think it's this all out crazy stuff, I'd never do it, it's a reframing of it for them.

Rhonda: Yeah.