The Norwegian 4x4 workout, step by step

What is the Norwegian 4x4 workout?

The 4x4 is an interval session built from four hard efforts of 4 minutes each. Norwegian researchers in Trondheim used it in a soccer study in 2001.^[2] In 2007 the same group tested it against steady running.^[1] The 2007 paper is the one most people mean when they say "the Norwegian 4x4."

VO₂max is your aerobic capacity, the most oxygen your body can use when you go all-out. The studies below tested the 4x4 as a way to raise it.

Here is the session as the Trondheim studies ran it.

1. Warm up for 10 minutes at about 70% of your max heart rate.^[3]
2. Run 4 minutes at 90 to 95% of your max heart rate.^[1]
3. Recover for 3 minutes at about 70% of your max. Keep moving.^[1]
4. Repeat until you have done four hard intervals and three recoveries.
5. Cool down for 5 minutes.^[3]

The 2007 study gives the hard minutes and the recoveries. A 2013 study from Trondheim added this warm-up and cool-down to its 4x4, and its hard intervals ran at 90% of max. The whole session took 40 minutes.^[3]

Where should your heart rate be in each interval?

The 2007 target was 90 to 95% of max heart rate.^[1] Say your max is 190. Then the hard minutes run from 171 to 181 beats a minute, and the recoveries come down to about 133.

Diastra's VO₂max band starts at 92% of max and runs up to your max. With a max of 190, the band starts at 175. The study's 90 to 95% target starts a little below that line and ends above it. Heart rate climbs through the first part of each interval, so it usually reaches the band only in the later minutes. Type your age below to see where your own VO₂max band starts.

The band is a heart rate range. The research measures time near VO₂max with a mask that reads the oxygen you breathe. These are two different measures, and time above a heart rate line runs longer than time near VO₂max. One study put 12 highly trained runners through four 3-minute intervals. Their heart rate stayed above 90% of max for about 9 minutes. Their oxygen use stayed above 90% of VO₂max for about 5 and a half minutes.^[7]

The band is also only as good as the max it comes from. A study of 3,320 healthy adults found that a max predicted from age alone had a typical error of about 11 beats a minute.^[8] This guide shows how to find the max your own workouts have already shown.

What did the 2007 study find?

Forty healthy, moderately trained men took part.^[1] The researchers split them into four groups. One ran long and slow at 70% of max. One ran steady at 85% of max. One ran 15-second bursts at 90 to 95% of max with 15 easy seconds between them. The last group ran the 4x4.

Every group trained three times a week for 8 weeks. Every plan used about the same total amount of oxygen.^[1]

The two interval groups came out ahead. The 4x4 group raised VO₂max by 7.2%, and the 15-second group raised it by 5.5%. Both interval groups gained clearly more than the slow group and the steady group.^[1]

The study also measured how much blood the heart pumped with each beat. That rose by about 10% after the interval training.^[1] Hard intervals train your heart to pump more blood with every beat. The changes in VO₂max matched the changes in blood per beat, and the authors saw a close link between the two.

What did the other Norwegian studies find?

The 2001 study tested the 4x4 in soccer. Nine elite junior players aged about 18 ran it twice a week for 8 weeks.^[2] They jogged for 3 minutes between the hard efforts. Their VO₂max rose from 58.1 to 64.3 mL/kg/min. That unit means milliliters of oxygen for each kilogram of body weight each minute. They covered 20% more ground in matches after the training block. The ten players in the control group showed no change.

Later work in Trondheim asked how little was enough. The group trained 26 inactive men aged 35 to 45 three times a week for 10 weeks.^[3] None of them had exercised regularly for at least two years. One group ran the full 4x4, and the other ran a single 4-minute interval. VO₂max rose 13% in the 4x4 group and 10% in the single-interval group. The gap between the two groups was small enough that it may have been chance.

Does the 4x4 work for women and older adults?

In 2023 researchers from the 2007 group ran two more trials with well-trained young adults. One trial split 48 men aged about 23 into three interval groups. The other split 81 women aged about 22 the same way. Every group trained three times a week for 8 weeks.

The men's 4x4 group raised VO₂max by 6.5%.^[4] The women's 4x4 group raised it by 7.3%.^[5] In both trials the 4x4 raised VO₂max more than two kinds of short sprint intervals.

These two trials set the hard minutes by speed. Each person ran at about 95% of the speed where they reached VO₂max in a lab test.^[4][5] The researchers in the men's trial changed the speed through the weeks so heart rate kept reaching 90 to 95% of max.^[4]

Older adults who reported hard training kept more of their fitness. Generation 100 was a five-year study of adults aged 70 to 77 in Trondheim. One of its groups trained twice a week with supervised intervals at about 90% of peak heart rate.^[6] A later analysis followed 500 people in the study who reported the same kind of training for all five years.

Peak oxygen use is the most oxygen their lab test measured. Women who reported hard training held their peak oxygen use level. Women who reported moderate training lost 4.6%. Men lost 3.1% with hard training and 7.7% with moderate training.^[6] That analysis sorted people by the effort they reported. Its hard group took in intervals and any other hard exercise.

Why does your heart rate lag at the start of each interval?

Your legs change speed in a second. Your heart rate takes longer to catch up, so it climbs through the first part of every interval. The 2023 trial with men aimed for 90 to 95% of max within 3 minutes of the start of each interval.^[4]

The lag leads to a common mistake. A runner glances at the watch early in the interval and sees a number well under the target. The runner speeds up to chase it, and heart rate keeps climbing anyway. A few minutes later the pace is too fast to hold, and the last interval falls apart.

The fix is to run the start of each interval by feel. Start at a pace that feels hard and steady, and let heart rate rise on its own. Check the number in the second half of the interval, and change the pace only then.

The wrist sensor also reads least clearly while heart rate is changing fast. A jumpy number early in the interval is one more reason to wait. The second half of the interval gives the cleaner read.

How do you run a 4x4 on a treadmill, a track or a hill?

On a treadmill. The 2013 study ran every session on a treadmill set at an incline.^[3] Set the incline first and leave it there. Then set a speed for the hard minutes and lower it for the recoveries. A small incline also brings the treadmill closer to running outside. Trained runners on a 1% incline used about the same oxygen as they did on a level road at the same speed.^[9]

On a track. Run the start of each interval by effort and the rest by heart rate. Jog the recoveries, and keep jogging even if it is slow. Aim for four even intervals. A fast first interval often leaves the last ones short of the band.

On a hill. Find a steady climb you can run up for 4 minutes. Run up hard, then jog or walk back down for the 3-minute recovery. A hill brings your heart rate up at a slower pace. The way down gives you the recovery without stopping.

A clean session looks the same on a heart rate chart on any surface. You see four distinct peaks at about the same height. The fourth peak reaches at least as high as the first. The low points between them stay level and do not creep upward.

How often should a runner do the 4x4?

The studies ran it two or three times a week. The 2007 men, the inactive men in 2013 and both 2023 trials did it three times a week.^[1][3][4][5] The soccer players did it twice a week.^[2]

Easy running builds the aerobic base the hard sessions stand on. The 80/20 guide shows how to keep a week mostly easy around a few hard sessions.

How long until VO₂max goes up?

Four of the trials lasted 8 weeks, and all four found clear gains by the end.^[1][2][4][5] The 2013 study measured its gains at 10 weeks.^[3] One session moves nothing you can measure. A few weeks of sessions show up as small changes that are easy to confuse with a good day.

A Cooper test before and after a block of training is one simple way to check. The 4x4 is one tool among several. The guide to improving VO₂max covers the rest, including the easy volume that makes the hard sessions work.

How Diastra handles a 4x4

Diastra finds your max heart rate in your own workouts, a guided test or a number you type. It draws your VO₂max band from that max. It holds you in your band on the Apple Watch with a tap when you drift out, and it credits only the minutes that held. Diastra also shows over the weeks whether your training is working ("Getting fitter. Holding steady. Slipping."), even when the answer is no.