How Norwegian 4x4 Intervals Improve VO2 Max
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In this clip from Dr. Rhonda Patrick's appearance on The Rich Roll Podcast, she explains why VO2 max is a useful measure of cardiorespiratory fitness and why vigorous intervals can complement steady aerobic work. The Norwegian 4x4 protocol uses four hard four-minute intervals separated by three minutes of active recovery, creating sustained time near a high aerobic intensity without requiring an all-out sprint.
Randomized training studies support this approach. In 48 well-trained men, eight weeks of 4x4 intervals increased VO2 max by 6.5%, more than two sprint-interval protocols. A separate study in inactive men found that both one four-minute interval and a full 4x4 session improved VO2 max after ten weeks, showing that meaningful adaptations can occur across different starting volumes. [1] [2]
A practical target is to let heart rate rise across each interval while keeping the pace sustainable enough to complete all four rounds. In a study of 39 active adults, the standard 4x4 session produced about 13 minutes within 85% to 95% of maximum heart rate. Dr. Patrick presents this as a focused way to train the upper end of aerobic capacity alongside easier endurance work, strength training, and recovery. [3]
This clip is excerpted, with permission, from Dr. Rhonda Patrick's appearance on The Rich Roll Podcast. Thank you to The Rich Roll Podcast for allowing us to share it.
- ^ Hov, Håkon; Wang, Eivind; Lim, Yi Rui; Trane, Glenn; Hemmingsen, Magnus; Hoff, Jan, et al. (2022). Aerobic High‐Intensity Intervals Are Superior To Improve V̇O 2Max Compared With Sprint Intervals In Well‐Trained Men Scandinavian Journal Of Medicine & Science In Sports 33, 2.
- ^ 10.1371/journal.pone.0065382
- ^ Acala, Justin J.; Roche-Willis, Devyn; Astorino, Todd A. (2020). Characterizing The Heart Rate Response To The 4 × 4 Interval Exercise Protocol International Journal Of Environmental Research And Public Health 17, 14.
Dr. Rhonda Patrick: Yeah. Vigorous intensity exercise is great for that reason, but it's also great because it is a way of improving our cardiorespiratory fitness, our cardiovascular health. And so, cardiorespiratory fitness is a measure of— it's usually measured in terms of VO2 max, as you know, and it's the maximum amount of oxygen that you can take in during maximal exercise. And cardiorespiratory fitness is really a marker. I personally think it's now, you know, emerging data over the last 5 years or so has proven that is probably the strongest marker we have of longevity today. You know, there's a lot of people out there looking at XYZ biomarker, your epigenetic age, you know, lots of different aging clocks, or your blood glucose levels, lots of different things that you can look at.
Dr. Rhonda Patrick: But it turns out that cardiorespiratory fitness really is the prominent marker for longevity. So if you're someone that's doing endurance exercise, like if you're an elite athlete, you know, these people are training like,
Rich Roll: What, 30 hours a week?
Dr. Rhonda Patrick: Yeah, on average.
Rich Roll: Yeah.
Dr. Rhonda Patrick: On average. For the majority of people that are really just sort of interested in health and fitness and perhaps, you know, don't have a lot of time to work out a lot, you know, they're barely trying to meet the minimum requirement of 2.5 hours a week of moderate-intensity exercise, let's say. Uh, they're really limited by time constraints, let's say, but they want to improve their VO2 max, they want to improve their cardiorespiratory fitness.
Rich Roll: So, what kind of exercise should they engage in to improve their cardiorespiratory fitness?
Dr. Rhonda Patrick: So, if you're doing something like 30 hours a week, that is something where you're splitting your time between doing cardiovascular endurance training, but also some high-intensity interval training. You're doing some vigorous-intensity exercise along with that as well. So, you're kind of covering all the bases. But for people that are not doing such long hours of training, there have been studies that have shown that even people that are meeting the 2.5 hours of moderate-intensity exercise per week, if they're only doing this sort of zone 2 training, where they're not really going into that vigorous zone, up to 40% of people have a hard time improving their VO2 max, and they're called non-responders.
Rich Roll: And so, why is that? Why are they not responding to cardiovascular, just simple endurance training, 70% max heart rate, let's say, or below?
Dr. Rhonda Patrick: So, about moderate-intensity exercise. And it's not really known why, but it's thought that the stress isn't great enough to cause the adaptations to allow them to improve their VO2 max. And so, when you take those non-responders and then have them engage in vigorous-intensity exercise, then they're able to improve their cardiorespiratory fitness. Again, coming down to that adaptation where you're putting a greater stress on the cardiovascular system, and therefore, your body is responding to that stress with a variety of different beneficial, you know, response pathways.
Dr. Rhonda Patrick: And so VO2 max, I would say, again, as a marker of longevity, one of the best ways you can improve that is by engaging in vigorous-intensity exercise. So that would be kind of the long-winded answer to the different types of, you know, endurance versus kind of more vigorous-intensity exercise, and why I think there's differences, but also, you know, there's some overlap as well.
Rich Roll: And what do we know, again, another, like, what do we know or not know about the impact of vigorous exercise versus endurance exercise on moving the needle on cardiovascular health?
Dr. Rhonda Patrick: I mean, they're both good for cardiovascular health, right?
Dr. Rhonda Patrick: You know, like, what I was mentioning was the cardiorespiratory fitness aspect, and the reason I was mentioning that is because almost half the population isn't responding to that if they're just doing the sort of moderate-intensity exercise where they're doing 70% of their max heart rate for 2.5 hours a week. I like to mention that because it seems a sizable part of the population really does need a little bit more stress for their body to adapt, for whatever reason. I don't know that that's well understood, but what is understood is that it does occur. And so, you know, I do think, again, you don't want to compare apples to oranges. So, like, a lot of times we'll look at what these endurance athletes are doing, and they're doing a lot of zone 2 exercise, right?
Dr. Rhonda Patrick: But they're doing a lot of it. So, I don't think you can compare someone who's doing over 10 hours a week—
Rich Roll: Oh, no, no. Yeah, I mean, yeah, nobody should really look at that as a benchmark to decide what they're going to do.
Dr. Rhonda Patrick: And, you know, those people, their zone 2 is very unlike the average person's zone 2 because they've been doing it for so many years and they've built this huge base. Like, their kind of, like, pace that they're able to maintain would be, you know, beyond the threshold of an average person. So, they're putting a— even though cardiovascularly they can handle it, putting an additional strain on their ligaments and their muscles and things like that. It's very different from the average person.
Rich Roll: Before we move on to microplastics, I think a good place to end this section of the podcast is to kind of explain specifically what vigorous exercise is, or high-intensity training. Like, what would a routine be for somebody who's never done this before, or where can somebody find examples of routines, uh, to begin this?
Dr. Rhonda Patrick: Okay, so there's a lot of examples of what a high-intensity interval routine would be depending on, like, what kind of interval you're looking for, what kind of outcome you're trying to improve, whether that's improving your cardiorespiratory fitness, your VO2 max, or you wanting to really get that BDNF increase, because there are studies that have really been shown to do, to do both of those things.
Dr. Rhonda Patrick: So I would say in terms of the VO2 max improvements, what's been shown to be the most beneficial is the Norwegian 4x4 protocol that I mentioned, because for whatever reason, the longer intervals of going as hard as you can for a longer period of time, this is not all out, it's as hard as you can go and maintain for that duration of 4 minutes, right? And so, it's gonna be different for everyone, but you kind of have to pace yourself, and you do that—
Rich Roll: And is that something you do on a treadmill, or a stationary bike, or a rowing machine?
Dr. Rhonda Patrick: You can do it on any of them. I've been doing it on a rowing machine, but it was actually, I think, you know, stationary bikes are what some of these other studies have shown as well. People can do running on a treadmill.
Dr. Rhonda Patrick: I mean, it really, you can kind of pick what you want, but the idea is you want to do 4 minutes at the intensity, at the highest intensity that you can maintain for that 4 minutes, which is not all out. You do recovery for 3 minutes at a very low intensity, and then you do that and you repeat it 4 times. So you do it 4 times. It's called the Norwegian 4x4. That's been shown to be one of the best ways to improve cardiorespiratory fitness. In that study where the heart aging was reversed by 20 years, those people did it once a week.
Rich Roll: Hmm.
Dr. Rhonda Patrick: And so, you can do that once a week, that's great. I do it on a Concept2 rower, but you can do it on a bike, you can do it, you know, whatever it is that works well for you that you will be consistent in doing that.
Dr. Rhonda Patrick: Now, I should also point out, if you've never really done high-intensity interval training before, you're gonna start out probably going a lot slower for your interval, and that's fine because you're basically—
Rich Roll: You're gonna have to because your capacity to recover during the rest aspect of the interval is not gonna be, you know, that great, right? So if you go too hard on the first one, you're not gonna make it through the rest of the set.
Dr. Rhonda Patrick: Exactly, yeah. And so for people that are interested in— there's, like I said, there's a lot of different protocols out there for vigorous-intensity exercise improving a variety of different parameters.
Dr. Rhonda Patrick: I do have a free guide called How to Train According to the Experts, and it's really according to all the experts that I've interviewed on my podcast in terms of, like, the different protocols for training and what they have been shown to improve. It's all evidence-based. People can find that out at howtotrainguide.com, and that's just a free guide.
Rich Roll: That's awesome.
Dr. Rhonda Patrick: It's got all the different protocols. And then there's another protocol for the BDNF, so that would be what you can do to increase your brain-derived neurotrophic factor. There's also a variety of protocols that have been shown to do that. One of 'em is going at least 80 to 85% your max heart rate for 20 to 30 minutes. And, um, that I believe was running, but I, you'd have to check.
Dr. Rhonda Patrick: I have a, a free guide on that, and that, that guide is called bdnfprotocols.com. And it's a variety of different protocols that have been, you know, shown to increase brain-derived neurotrophic factor. If people are really specifically looking for that type of protocol, which is something, like I said, I myself am interested in looking at.
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