Heard the words “Norwegian 4x4” while refilling your water bottle at the gym or on social media recently?
You’re not imagining things - this high-intensity interval training method has become the talk of fitness circles in the last month, after biochemist Dr Rhonda Patrick described it as the “gold standard” for boosting cardiovascular fitness on her episode of Diary of a CEO at the end of July.
Since then, it’s been flooding our feeds, thanks to the claims that it not only levels up your cardio but also makes your heart younger in the process.
The great news is that the Norwegian 4x4 isn’t a fitness fad. Used as a training method in over 200 clinical studies, it’s one of the most researched interval workouts out there. In fact, a landmark two-year study found that following it consistently could reverse two decades’ worth of heart ageing in sedentary adults.
It’s all thanks to the workout’s effects on VO2 max, which is a measure of how efficiently your body uses oxygen during exercise, and has been closely linked to greater longevity.
If this is all starting to sound a bit technical, don’t worry. If you’ve ever completed a one-minute-on, one-minute-off spin class or sweated your way through a Tabata session, you’ve already tapped into the same training principles used in the Norwegian 4x4. But it’s the very specific structure of the workout, coupled with its extensive research-backed results, which make it stand out from your average HIIT circuit.
So, is it really a session we should all be trying? We asked two expert personal trainers to break down exactly how it works, why we’re all talking about it, and whether it’s worth adding to your weekly routine.
And if viral fitness challenges are your thing, we’ve got expert-led takes on the 75-hotter, Operation 66 and Winter Arc challenge. Plus, be sure to read up on our review of the best fitness trackers before you invest yourself (spoiler: they come in handy for the Norwegian 4x4).
The Norwegian 4x4 Workout is Trending, But Is It Really The Key To Longevity?
What is the Norwegian 4x4 workout?
If “Norwegian 4x4” sounds Viking-esque, let me reassure you that the reality is far less intimidating. It’s undoubtedly high intensity, but it’s also a safe and structured method designed to get you working just below your all-out max.
Formulated in the 1990s by exercise physiologists Dr Jan Hoff and Dr Jan Helgerud, the workout is built around specific heart rate zones. “The Norwegian 4x4 involves four cardio intervals of four minutes, each completed at 85-95% of your maximum heart rate,” explains personal trainer and Castore ambassador James Stirling. “You then recover for three minutes between each round, keeping your heart rate at around 70%.”
The great news is that “the workout can be adapted for running, cycling, swimming, rowing or traditional gym workouts,” adds Andy Carr, master trainer and head of fitness at Snap Fitness UK, which means that although the time and intensity of the workout are prescribed, you can choose whichever kind of cardio works best for you. You just need to make sure you can keep doing it at a high intensity for four minutes, which, when you’re pushing hard, is much longer than you think.
What are the benefits of the Norwegian 4x4 workout?
There are two major benefits to the Norwegian 4x4: its efficiency and its impact on your VO2 max.
You see, research since the Dallas Bed Rest Study back in 1966 has consistently shown that a sedentary lifestyle is one of the main contributors to poor cardiovascular health and premature heart ageing. In fact, the original study found that just three weeks of bed rest could age someone’s heart by the equivalent of 30 years. Fast forward to today, and with more of us hunched over laptops for eight-hour stretches, moving less and lacking the time to exercise, the health of our hearts is an area of growing concern for doctors and researchers.
That’s where the Norwegian 4x4 comes in. Taking just 25 minutes to complete, it’s an evidence-based “versatile option for those who want a quick and efficient workout to fit around their schedule,” explains Carr. Adaptable for indoor and outdoor cardio, it’s also a workout you can do year-round, making it perfect for when the darker nights close in and a run on the road doesn’t appeal.
You might be wondering why you can’t just go for a steady run or spend 45 minutes on the Stairmaster to tick off your cardio. You absolutely can - these workouts offer plenty of benefits for your overall health, from improved body composition to muscle strength, bone health and mental wellbeing. It’s just that, when it comes specifically to heart health and cardiovascular fitness, some studies suggest the high-intensity intervals used in the Norwegian 4x4 are more effective than both sprint training and steady-state cardio for long-term health and longevity.
Are there any risks to the workout?
It’s important to remember that the Norwegian 4x4 isn’t an entry-level workout.
“The main risk is general overexertion,” says Carr. “Four minutes is quite a long period to sustain high intensity activity, so if you go too hard too often, and don’t give your body sufficient time to recover, you could find yourself fatigued.”
For this reason, Stirling doesn’t advise the workout for beginners. “Before you attempt the 4x4 workout, make sure you have a base level of fitness and start with fewer intervals.”
Stirling adds that for those prone to injuries, it may be best to try the intervals on a bike, rowing machine or elliptical, rather than running, to avoid too much impact.
It’s also why proper warm-ups and cool downs are particularly important for those trying the 4x4 workout, and it’s important not to rush through these to get to the main session. “It’s very important to listen to your body,” adds Carr. “If you’re still feeling tired and achy from a previous session, more rest is important. If you notice any sharp pains or a noticeable feeling of fatigue, these are signs to reduce your intensity or stop.”
For women in particular, there may be concerns about the effect that the Norwegian 4x4 could have on our hormone health. In recent years, high-intensity workouts have fallen out of favour, with many of us choosing gentler forms of movement to reduce the stress on our nervous system.
But for personal trainer Aimee Victoria Long, the key is in finding balance. “The answer isn’t to choose one over the other, but to consider blending them,” she explains. “For most women, one Norwegian 4x4 session each week is more than enough, layered on top of a foundation of low-intensity movement, such as Pilates and walking, which are fantastic for hormone balance, regulating the nervous system and creating consistency.”
What do you need to know before giving it a go?
The key to doing this workout properly and safely is understanding your heart rate. Specifically, your maximum heart rate (or HRmax), which you can estimate by subtracting your age from 220. So, if you're 30, your HRmax would be around 190.
Why does this matter? Because “training above your threshold can be dangerous,” warns Carr, as it places too much stress on your cardiovascular system, which can lead to dizziness, nausea, chest pain and in the most extreme cases, arrhythmias or heart attack.
It’s why the experts recommend wearing a heart rate monitor if you’re going to try the method, in order to remove the guesswork. “Most heart rate monitors estimate your HRmax automatically, which makes it easier to track intensity,” says Stirling.
That said, you can go old-school and use perceived effort - you just have to be prepared to tune in to your body. “In terms of a feeling, working out at 85-95% of your maximum intensity will leave you out of breath and struggling to talk,” explains Carr.
For some women, it may also help to be aware of where they are in their cycle, adds Long. “Using the follicular phase when energy is often naturally higher to push harder, with workouts like the Norwegian 4x4, can work for some. You could then consider easing back during the luteal phase when your body may benefit more from restorative training.”
Our verdict
As a Health Writer who’s tested more than her fair share of viral workouts, I’d say the Norwegian 4x4 workout is one of the few you should pay attention to. It’s less of a trend and more of a training principle, rooted in published scientific research, and focusing on measurable factors proven to improve cardiovascular fitness.
But it is hard, and that shouldn’t be forgotten. This is the kind of workout that should be built up to over time, and even then should be carefully planned into your week. Take the experts’ advice and combine one to two sessions of the Norwegian 4x4 with lower-impact, gentler forms of movement, such as Yoga and Pilates, to help your body recover.
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How many times a week should I do the Norwegian 4x4 workout?
“The experts who formulated the workout recommend a minimum of two sessions a week, which ensures you have enough recovery time whilst providing your body with enough stimulation to see cardiovascular improvements,” says Andy Carr, master trainer and head of fitness at Snap Fitness UK.
That being said, “even completing the workout once a week, when used in addition to your usual workouts, can lead to additional fitness benefits,” he explains, reminding us that all movement is beneficial, even if the two sessions feels difficult due to fitness level or time.
For women specifically, personal trainer Aimee Victoria Long agrees that one session a week is ideal for creating a balance between cardiovascular fitness and nervous system regulation. “The Norwegian 4x4 works beautifully as a supplement rather than the core of a programme,” she says. “For most women, one interval session like this each week is more than enough, layered on top of a foundation of low-intensity movement.”
“Balance your sessions with strength training, steady-state cardio, and mobility work,” adds personal trainer and Castore ambassador James Stirling. “Not every session has to be high intensity, and the combination of workouts supports recovery, prevents burnout and helps to avoid injury.”
