Every so often, a new type of workout seemingly takes the fitness world by storm. The latest in this long line of buzzy fitness fads: the Norwegian 4×4 workout, a high-intensity interval training (HIIT) method that’s become the exercise trend du jour. Developed by researchers at the Norwegian University of Science and Technology in the 1990s, the Norwegian 4×4 blew up recently thanks in part to Rhonda Patrick, PhD, a biochemist and the creator of the Found My Fitness podcast and newsletter.
In an August 25 YouTube video provocatively titled “This Workout Reverses 20 Years of Heart Aging,” Dr. Patrick talks with host Tim Ferriss about the Norwegian 4×4’s benefits. Even if you hadn’t heard of the workout before, the video’s title—and the bold assertion baked in—might have piqued your interest. To help you learn more about it (and confirm whether that big heart claim is legit), we’ve compiled everything you need to know about the Norwegian 4×4.
What does the Norwegian 4×4 entail?
Like other HIIT workouts, the Norwegian 4×4 consists of brief spurts of high-intensity exercise interspersed with active recovery periods, but it’s distinguished by a “longer work interval” of four minutes (compared to other HIIT workouts with shorter bursts of, say, 20 to 30 seconds), McDonald says.
It starts with a 10-minute warm-up at a low to moderate intensity to raise your heart rate. “You want to prepare your body for what’s going to be a very strenuous workout, especially on the cardiovascular system, ahead,” Tyler McDonald, NASM-CPT, CNC, a certified personal trainer specializing in tennis, and a senior brand marketing manager for the National Academy of Sports Medicine, tells SELF.
Then, you segue into the first work interval by exercising for four minutes at the highest intensity you can maintain for that amount of time. Choose any exercise you want, from running and cycling to swimming and rowing). “You can also adapt this to an assault bike or a kettlebell circuit or something of that nature,” McDonald says. Some people even start off with brisk walking, Dr. Patrick says in the YouTube video, “so it’s all tailored to the individual.” Whatever exercise type you choose, aim to hit around 85% to 95% of your maximum heart rate, Jeswin Jacob, DO, a sports medicine physician in the University of Pittsburgh Medical Center’s orthopedics section, tells SELF.
Follow that with three minutes of light exercise to lower your heart rate, Dr. Jacob says. Repeat this four-minutes-on, three-minutes-off regimen a total of four times (hence the “4×4” in the name). Finally, end with a 5- to 10-minute cooldown.
The entire workout (including the warm-up and cooldown) takes around 40 minutes, according to McDonald. Brief but demanding, it could be a smart choice for those “who have limited workout time and want to get an efficient workout in,” Dr. Jacob says.
What health benefits does it have?
There are two main perks associated with the Norwegian 4×4: better heart health and a higher VO2 max. (VO2 max is a measure of how much oxygen your body consumes during intense exercise and is a key indicator of your fitness level and cardiovascular well-being. What’s more, a high VO2 max has also been linked to a longer lifespan.)
By pushing your aerobic limits, the Norwegian 4×4 extends your “ability to sustain physical activity,” McDonald says. “It makes your heart a lot stronger and better at pumping blood through your body,” he explains. In turn, these heart health improvements can help lower your resting heart rate, cardiovascular disease risk, blood pressure, and cholesterol levels.
Research backs these claims. In a 2018 study (referenced by Dr. Patrick in the YouTube video), researchers assigned healthy but sedentary middle-aged men to exercise training four to five days per week for two years. Each exercise session had to span at least 30 minutes, and at least one 4×4 workout was mandated per week. By the end of that time, participants’ VO2 max had improved and their cardiac stiffness—a major risk factor for cardiovascular events—was down. Notably, the same benefits were not observed in a control group assigned to balance and flexibility training (think yoga and stretching) three times per week for two years.
While the study didn’t directly reference the 20-year figure cited by Dr. Patrick, it did note that the protocol seemed to “reverse the effects of sedentary aging on the heart,” resulting in “considerable cardiovascular benefits” overall (potentially including a lower risk of heart failure).
Even compared to other HIIT workouts, the Norwegian 4×4 may be particularly effective for VO2 max due to the fact that the longer work intervals demand more stamina. One 2016 study found that the 4×4 method was better at boosting the metric than a 10×1 HIIT workout (one that consists of 10 sets of one-minute work intervals)—a finding attributed to the enhanced “stroke volume,” or the amount of blood the heart pumps per beat.
That said, all HIIT workouts will benefit VO2 max and heart health to some extent—so, as Dr. Jacob says, don’t make the mistake of thinking the Norwegian 4×4 is the only one worth doing.
Who is the Norwegian 4×4 best for?
Thanks to the outsized effect on VO2 max, the Norwegian 4×4 is excellent at building endurance, according to McDonald. (On the flip side, “it may be inferior” for strength and explosive power, Dr. Jacob says.)
Because of this emphasis on endurance, McDonald says, the Norwegian 4×4 is most well-suited to “those people who are really trying to maintain maximum performance for a very long duration of time—your marathon runners, your triathletes, your long-distance swimmers.” McDonald uses it to help the tennis players he trains develop the skills necessary to play a full match at a competitive level.
By contrast, “I would not suggest it for the beginners or even just your everyday gym-goer,” McDonald says. “Smaller-interval HIIT or Tabata-type workouts will be just as beneficial.” If you’re not persuaded by this argument (or just want to try the Norwegian 4×4 for the sake of joining in on the trend), check in with a healthcare professional first, especially if you have a health condition. “People with heart or lung conditions need to get medical clearance from their doctor, as there is high demand on the heart and lungs during this routine,” Dr. Jacob says. “Don’t go into it just assuming your heart can handle this,” McDonald adds.
If you do get the green light, start slow, “with a shorter-intensity interval and increased time for your warm-up period,” Dr. Jacob says. “Those who are new to the workout [specifically] should begin with caution due to increased risk of injury as well.”
What should you keep in mind as a newcomer?
Don’t skip (or skimp on) the warm-up.
Diving right into the first exercise interval might be tempting, but you’ll regret bypassing this initial step, according to Dr. Jacob. Not only does warming up help prevent injury, research shows it also makes your workout more effective, as SELF previously reported. While any kind of warm-up is helpful, one that takes the form of a lower-intensity version of the actual workout—like a light jog if you’re planning to sprint on the treadmill—will deliver the best results. “It does help prepare the body a lot better,” McDonald says.
Avoid going too hard too soon within an individual workout…
Since the goal is to “sustain high intensity for the full four-minute interval,” McDonald says, it’s crucial to find a middle ground between pushing yourself so you reap the benefits and pacing yourself so you don’t burn out early on. If you’re running on the treadmill, for example, “you don’t want to just all-out sprint that first 30 to 60 seconds and then fade down in the back half,” he says. While it might take some trial and error, finding the right tempo will pay off.
…or within the broader routine.
If you’re eager to see results, you might be tempted to do the Norwegian 4×4 as much as possible (say, on a daily basis), but maintaining that sort of fast clip is neither sustainable nor advisable. “Working out too frequently every day or not resting can lead to overtraining,” not to mention a high risk of injury, Dr. Jacob says. In fact, HIIT workouts are only recommended two to three times a week, according to Harvard Health.
Don’t take it too easy during the recovery intervals.
“Those three-minute periods in between the high-intensity workout [intervals] should not be a walk in the park,” McDonald says. Just because they’re technically breaks from the high-intensity stuff doesn’t mean you should take advantage of them by coming to a full stop. Instead, McDonald says, “you want to keep your body moving at a decent pace” to maintain an elevated heart rate.
Make hydration a priority.
During the Norwegian 4×4, “you burn a lot of calories and you sweat a lot,” McDonald says. To make up for these pronounced fluid losses, make sure you’re drinking water or another beverage on a continual basis so you don’t become dehydrated (and if you feel thirsty, it’s already too late). Downing seven to 10 ounces every 10 to 20 minutes is a solid rule of thumb, according to both the American Council on Exercise and the National Athletic Trainers’ Association, as SELF has previously reported. “You want to make sure you’re properly fueled for your performance and recovery,” McDonald says.
Wear a heart rate monitor.
Donning a device like a heart rate monitor isn’t always practical, but “definitely try to use one when possible,” McDonald says. Tracking your heart rate in real time will help you make sure you’re reaching the target intensity zone. Otherwise, “you could train underneath the targeted heart rate or even above,” potentially hurting the effectiveness of your workout, Dr. Jacob says.
Listen to your body.
It’s easy to try to tough it out to the end of a workout despite a flurry of warning signs, especially when the exercise interval is so deceptively short, McDonald says. Toxic gym culture glorifies pushing through discomfort, as epitomized in sayings like “No pain, no gain” and “Go hard or go home.” “But if your body can’t do it, your body can’t do it,” McDonald says—and no workout is worth endangering your health over.
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