HIIT vs. Moderate Intensity Exercise - Which Is Better for Your Health? | Dr. Martin Gibala

**Dr. Martin Gibala** (0:00)
So many people are struggling to meet the physical activity guidelines. We should all be doing about 150 minutes a week of moderate to vigorous physical activity intensity.

**Dr. Gabrielle Lyon** (0:10)
People struggle with time, so where would that be acceptable?

**Dr. Martin Gibala** (0:13)
There's a number of people, for you given the option, an hour of traditional continuous, or you can do 10 minutes of really vigorous. Which do you like? I really don't like that sprint training in the moment, but I certainly like it when I'm done in 10 or 15 minutes, and I would much prefer that to doing an hour or 90 minutes of the traditional approach. The studies also show that more vigorous physical activity will lead to greater improvements in VO2 max, and that's not only in healthy individuals, this is in individuals with many different chronic conditions.

**Dr. Gabrielle Lyon** (0:48)
Talk to me about where high-intensity interval training could be applied to the regular person.

**Dr. Martin Gibala** (0:56)
It all comes back down to do you have metabolic flexibility or not? One of the best ways to improve that is to boost your mitochondrial capacity, right? Boost your health.

**Dr. Gabrielle Lyon** (1:05)
We're entering a new era where people are very interested in female-specific exercise. Are there some differences?

**Dr. Martin Gibala** (1:12)
There might be some subtle differences there, but overwhelmingly, it's...

**Dr. Gabrielle Lyon** (1:26)
Dr. Martin Gibala, welcome to the show.

**Dr. Martin Gibala** (1:28)
Nice to see you again.

**Dr. Gabrielle Lyon** (1:30)
Now, one reason out of many I wanted to have you on the show is that high intensity interval training, sprint interval training, all of these modalities, what we're really after are outcomes, and you are arguably one of the world leading experts in these various types of exercises.

**Dr. Martin Gibala** (1:50)
Well, it's great to be back. You're too kind with your opening remarks there, but happy to get into it, and I really appreciate the opportunity.

**Dr. Gabrielle Lyon** (1:57)
So we're going to talk really basics, and then we can get into some of the more controversial aspects, because as we think about evolving science, one of the criticisms that we've heard over and over again is that there just is just not a lot of large data sets, highly powered studies, but before we get into that, let's just talk about what it is, high intensity interval training.

**Dr. Martin Gibala** (2:20)
Yeah, so to me, interval training is just alternating periods of higher intensity activity with recovery, so that can be all out rest or lower intensity exercise. High intensity, it really depends, are you talking in a performance context or in a health context? And so in a health context, exercise prescription, we talk about light, moderate, vigorous intensity exercise. And so vigorous intensity exercise is that high intensity range. And so we can use different metrics. The WHO, World Health Organization, would say on a to 10 scale, vigorous exercise is a 7 or 8 out of 10

**Dr. Gabrielle Lyon** (3:05)
That's defined differently for everybody.

**Dr. Martin Gibala** (3:07)
Correct. Moderate is a 5, right? We also have other RPE scales, classic 6 to 20 scale. Their vigorous is a 14, 14 to 17 If we're talking heart rate ranges, you know, in the American College of Sports Medicine would have authoritative guidelines. We're talking a heart rate of about 77% of your maximum or above. And there's also percentages of VO2 max as well. The point being, there's no single best indicator of what counts as hit. People can use RPE, people can use heart rate, people can use measurements of VO2 max. And so all of those are anchored to some maximum physiological threshold, your VO2 max, your heart rate max.
Now, if you're an athlete, you don't talk like that. Or coaches and athletes will talk about three fundamental domains, moderate, heavy, severe. And so once you get into the severe domain, that is high intensity exercise. And in the severe domain, it's generally not exercise, it's sustainable, it's non-steady state exercise. And so athletes and coaches talk about, this is really important, I think, metabolic thresholds. So things like your lactate threshold, your ventilatory threshold. And so high intensity exercise, if you're an athlete, is your second lactate threshold, your maximal lactate steady state, your critical power. And so importantly, those are physiological measures, metabolic characteristics, that then they will anchor heart rate RPE2 for them. And so I think this is the real problem when we start talking about zone training, that it's so variable for everyone. And so unless you happen to actually know your lactate threshold, your fat max, you're sort of just guessing.