The Norwegian 4x4 Workout: What It Is and How to Do It

The Norwegian 4x4 is an interval workout: a 10 minute easy warm-up, then 4 rounds of 4 minutes hard at about 85 to 95% of your max heart rate, with 3 minutes easy between each round, then a cool-down. It was developed by the Cardiac Exercise Research Group at NTNU in Trondheim, Norway, as a way to build your VO2max, your engine.

I'm Swedish, so it costs me a little to say the Norwegians got something right. This is one of those things. But there are TWO "Norwegian" things floating around the internet, and you only need one of them.

What is the Norwegian 4x4 workout?

Here's the whole thing:

• 10 minutes easy to warm up
• 4 minutes hard, 3 minutes easy
• Repeat for 4 rounds
• Cool down easy

"Hard" means you can say about three words. Not a sentence. Not a TED talk. Three words. If you're chatting, you're not there yet.

Why does VO2max matter for longevity?

VO2max is the most oxygen your body can take in and use during hard exercise. Think of it as one number for your whole engine: heart and muscles working together.

And it's a BIG deal:

• In a meta-analysis of 33 studies, about 103,000 healthy adults, each step up in fitness (1 MET) was linked to 13% lower risk of death from any cause and 15% lower heart disease risk. The least fit had 1.7 times the death risk of the fittest.
• In women averaging 52, each step up meant about 17% lower risk of death.
• Elite fitness was linked to about 80% lower mortality than the lowest fitness, with no upper limit to the benefit.

Fitness also falls with age, and the fall speeds up: 3 to 6% per decade in your 20s and 30s, more than 20% per decade from your 70s, at every activity level. Training pushes that curve back up. (Most of this is observational, so it shows links, not proof of cause. Still. I know which side of that curve I want to be on.)

Does the 4x4 actually work better than steady cardio?

In the studies we have, it raised fitness more:

• Young men: in an 8 week study of 40 moderately trained men, only the interval groups raised VO2max more than steady training. The 4x4 group gained 7.2%, and the heart pumped about 10% more blood per beat. That study was men only, so keep that in mind.
• Heart failure patients averaging about 75: after 12 weeks, fitness rose 46% with intervals vs 14% with moderate steady training, and only the interval group's hearts improved in structure and pumping.
• Adults in their 70s: in Generation 100, about 1,500 adults aged 70 to 77 did twice-weekly 4x4s, moderate training, or their usual activity for 5 years. The interval group had the biggest fitness gains and better quality of life. There was a trend toward lower mortality, but it wasn't statistically significant. Honest summary: a trend favouring intervals, not proof.

So when someone tells you you're "too old" for high-intensity intervals.... the 4x4 was literally tested in people in their 70s and in heart patients averaging 75. Too old is a belief, not a fact.

How hard should the 4x4 feel, and what's my max heart rate?

Hard enough for about three words. In heart rate terms that's roughly 85 to 95% of your max.

Please stop using 220 minus your age if you're a woman. In a study of 5,437 women, peak heart rate followed 206 minus (0.88 x age). At 50 that's about 162 bpm, so 85 to 95% lands roughly between 138 and 154. If your watch has measured your real max, use that instead.

How we pace it in PRYME: 8 out of 10 (85 to 90% of max) for most of the cycle, and 9 out of 10 (90 to 95%) near the end. You don't start at the full 4x4 either. You build up from 2 or 3 shorter rounds to the full 4 rounds of 4 minutes. When you're a few weeks in and that third round feels doable instead of terrifying, you'll get why we build it.

Is the 4x4 the same as the elite "Norwegian method"?

No. Completely different animal.

The "Norwegian method" you hear about with the Ingebrigtsen brothers and Olympic triathlon champion Kristian Blummenfelt is built for full-time endurance athletes. It usually means 3 to 4 threshold interval sessions plus one very hard session a week, often two threshold sessions on the same day ("double threshold"), on top of 150 to 180 km of running a week. Pace is set by finger-prick blood lactate tests every 1 to 3 repetitions. The evidence mostly describes what elite athletes do. It hasn't been tested in everyday adults.

You are (I'm guessing) not running 150 km a week. You're lifting heavy three times a week, doing power work, and living a life. So you take the 4x4 from the health research and you leave the lactate meter to the Olympians.

How often should you do the Norwegian 4x4?

Once a week, if you also lift. Generation 100 used two interval days, but those people weren't doing 3 heavy lifts plus power work. Your lifts need recovery too.

Here's the week we build in PRYME, same for every age and life stage:

• One interval day, building to the full 4x4
• One easy session at full-sentence pace
• One optional long easy session
• Deload weeks with no hard rounds

Mostly easy, a little hard. Any machine works: run, bike, row or SkiErg. Fuel it with carbs and protein 1 to 3 hours before. Never do intervals fasted. For the bigger case on why every woman needs cardio, read [should women over 45 do cardio?](/blog/should-women-over-45-do-cardio), and for the VO2max deep dive, [VO2 max training for women 40, 50 and 60](/blog/vo2-max-training-women-40-50-60).

This isn't medical advice. If you have a heart condition or take blood pressure medication or beta-blockers, talk to your doctor first and go by effort (the three-word talk test) instead of heart rate numbers until you're cleared. Chest pain, fainting, palpitations or unusual breathlessness: stop and get urgent care.

Quick answers

What is the Norwegian 4x4? Four rounds of 4 minutes hard with 3 easy minutes between, after a 10 minute warm-up. It comes from heart research at NTNU in Trondheim.

How hard is the 4x4 supposed to be? About 85 to 95% of your max heart rate, or hard enough that you can only say about three words.

What's the best max heart rate formula for women? 206 minus (0.88 x age), from data in 5,437 women. That's about 162 at age 50. A measured max from your watch is better.

Can I do the 4x4 twice a week? If you lift heavy three times a week, one interval day is the design. More hard days tend to wear people down and stall progress.

Should I train like the Ingebrigtsens? No. Their double threshold, lactate-tested method is built for full-time endurance athletes, not for someone lifting heavy three times a week.

Sources. Kodama S, et al. Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women: a meta-analysis. JAMA. 2009. Gulati M, et al. Exercise capacity and the risk of death in women: the St James Women Take Heart Project. Circulation. 2003. Gulati M, et al. Heart rate response to exercise stress testing in asymptomatic women. Circulation. 2010. Mandsager K, et al. Association of cardiorespiratory fitness with long-term mortality among adults undergoing exercise treadmill testing. JAMA Network Open. 2018. Ross R, et al. Importance of assessing cardiorespiratory fitness in clinical practice. Circulation. 2016. Fleg JL, et al. Accelerated longitudinal decline of aerobic capacity in healthy older adults. Circulation. 2005. Helgerud J, et al. Aerobic high-intensity intervals improve VO2max more than moderate training. Medicine & Science in Sports & Exercise. 2007. Wisløff U, et al. Superior cardiovascular effect of aerobic interval training versus moderate continuous training in heart failure patients. Circulation. 2007. Rognmo Ø, et al. Cardiovascular risk of high- versus moderate-intensity aerobic exercise in coronary heart disease patients. Circulation. 2012. Stensvold D, et al. Effect of exercise training for five years on all cause mortality in older adults: the Generation 100 study. BMJ. 2020. Berglund I, et al. The Generation 100 study (HDL cholesterol, per protocol). Mayo Clinic Proceedings: Innovations, Quality & Outcomes. 2021. Casado A, et al. Does lactate-guided threshold interval training within a high-volume low-intensity approach represent the "next step" in the evolution of distance running training? International Journal of Environmental Research and Public Health. 2023. CERG, Norwegian University of Science and Technology (NTNU).