How Vigorous Interval Training Improves Heart Fitness

Steven Bartlett: The question is, how do you improve your cardiorespiratory fitness?

Dr. Rhonda Patrick: Do you lift weights? Do you go for runs? Do you bike? What is really good at improving cardiorespiratory fitness? That's a question that many exercise physiologists have answered over the last couple of decades.

You want to engage in what's called vigorous-intensity exercise. This is the kind of exercise where you're not able to have a conversation while you're doing it. Your heart rate is going up to around 80 percent of your maximum. You're not able to really talk. I would say it's something that can be done in intervals. You can do high-intensity interval training, with intervals where you're getting your heart rate up and doing vigorous exercise, followed by recovery periods where you're resting, lowering your heart rate, and not doing maximal exercise.

I say this because multiple studies have shown that some people who engage in moderate-intensity exercise, the kind of exercise where you're breathy but can still have somewhat of a conversation, cannot improve their cardiorespiratory fitness.

Steven Bartlett: Like the StairMaster.

Dr. Rhonda Patrick: Like the StairMaster. Exactly. Even among people who engage in that type of exercise for two and a half hours a week, following the physical-activity guidelines, 40 percent cannot improve their cardiorespiratory fitness. I don't want it to be a coin toss. If I'm doing that kind of exercise, I don't want a 50 percent chance of not improving my cardiorespiratory fitness. I want the sure thing.

You take those people and have them engage in high-intensity interval training, and they're able to improve their cardiorespiratory fitness. That's because you're putting a stronger stress on your cardiovascular system, so the adaptations are greater. Part of the adaptation is that you're able to bring in more oxygen and carry it to your muscles and other tissues better. That's your cardiorespiratory fitness.

The bottom line is engaging in it even once or twice a week. I would say the most well-researched protocol is called the Norwegian 4x4. You do a longer, four-minute interval. It's best done on a stationary bike or maybe a rowing machine. You're going as hard as you can while maintaining that intensity for four minutes. Then you go down to light exercise and recover for four minutes, letting your heart rate come down. You do that four times, so it's a four-by-four. That is probably one of the most robust ways to improve cardiorespiratory fitness.

But there are other ways, including one minute on and one minute off. You do one minute as hard as you can maintain for that entire minute. You're not going all out, but you're going as hard as you can and maintaining it for the entire minute. Then you rest for a minute. You do that 10 times, so it's a 20-minute workout.

Steven Bartlett: For the several million people listening right now, if you had to prescribe them all something to do, and it was the minimum they had to do, what exactly would the workout look like and how frequently would they do it each week?

Dr. Rhonda Patrick: I would say the minimum effective dose would be once a week.

Steven Bartlett: Okay.

Dr. Rhonda Patrick: It would probably be the one minute on, one minute off. If you want the upper end of robust effects for improving cardiorespiratory fitness, you can still improve it with something like a Tabata.

Steven Bartlett: What's a Tabata?

Dr. Rhonda Patrick: You do a 20-second interval and go more all out because it's a shorter time. Then you recover for 10 seconds.

Steven Bartlett: So it's 20 seconds on and 10 seconds off.

Dr. Rhonda Patrick: You do that eight times. If you repeat it twice, it's essentially a 10-minute workout. That's also something that can improve cardiorespiratory fitness. But I would say, and I'll tell you why, there is the minimum of one minute on and one minute off, but the Norwegian 4x4 is the gold standard.

That's because it's not only improving cardiorespiratory fitness. This is probably one of the most exciting pieces of evidence I've seen with respect to exercise and aging. Being part of an exercise protocol was shown to reverse the structural changes that occur with age in the heart by 20 years.

What do I mean by that? People who were 50 years old and sedentary were not going to the gym or engaging in physical activity, but they didn't have diseases such as type 2 diabetes or cardiovascular disease. I would argue that being sedentary is a disease, but putting that aside, they didn't have any diseases. They were in midlife.

This was done by Ben Levine at UT Southwestern in Dallas. He took these 50-year-olds and put them on a fairly intense exercise routine for two years, or a stretching routine as the control. The exercise routine was progressive. They started lighter and worked their way up. You don't want people who have never exercised to start with a Norwegian 4x4. That's going to be tough.

Toward the end of the first six months, these people were exercising about five to six hours a week. That included one or two sessions of the Norwegian 4x4. It also included a lot of moderate- to vigorous-intensity cycling or running and some strength training. They did this for two years.

Their hearts were examined. As we age, our hearts shrink and get stiffer, and that plays a role in cardiovascular disease. That's the number one killer in the United States. It also affects cardiorespiratory fitness. Why does the heart stiffen with time? It has a lot to do with being exposed to glucose. When you're eating a lot of refined sugar and refined carbohydrates, you have a lot of glucose in your system. This causes a chemical reaction called glycation. You get advanced glycation end products that react with collagen in the heart and myocardium, causing it to stiffen. The heart then can't respond to stress as well. It's stiff, and that plays a role in events such as heart attacks.

Exercise is one of the best things you can do to move glucose out of your vascular system and into your muscles. That's one of the things it does, and it helps prevent that stiffening of the heart. Essentially, after two years of this exercise protocol, the structure of these 50-year-olds' hearts was bigger and less stiff. It made their hearts look like those of 30-year-olds. That's amazing. You can take someone in midlife, put them on a two-year training protocol, and reverse the aging of their heart by 20 years.

Steven Bartlett: You've convinced me to give the Norwegian 4x4 a try. Specifically, how do I do it? I warm up, then do four minutes of hard exercise and take a break. The exercise in those four minutes can be any number of things, but do I just have to get to 80 or 85 percent of my exertion level?

Dr. Rhonda Patrick: As I mentioned, it's best if you're doing cardiovascular exercise.

Steven Bartlett: Like the assault bike.

Dr. Rhonda Patrick: You could do an assault bike. You can do a rowing machine or a stationary bike as well.

Steven Bartlett: Could I run?

Dr. Rhonda Patrick: You can, but I think it's better on a bike or an assault bike. You can run, though. Whatever you like to do, you go as hard as you can for those four minutes while maintaining it for the full four minutes. It's far from all out, but you're not really having a conversation while you're doing it.

During the four minutes of recovery, if you're running, you go down to walking. If you're on the rowing machine or assault bike, you go very slowly. You let your heart rate come down. You let your muscles and cardiorespiratory system recover somewhat. After that four-minute recovery, you return to four minutes of intense exercise. You do that four times.

It's not easy. People don't have to go extremely hard at first. Even if you start those four minutes at an intensity where you can still have a conversation, you're still going harder than you're used to pushing yourself. For people who haven't engaged in high-intensity training before, that's a good idea. You can't just start doing it right out of the gate. You want to work your way up.

During those four minutes, put in as much effort as you can. Then do your recovery and repeat it four times. Work your way up as you do it. One week, two weeks, a month, or two months later, try to reach the point where you're pushing yourself hard enough during those four minutes that you're not really able to have a conversation.