The science-backed method from NTNU researchers — shown to raise VO2max about 10% in 8 weeks (Helgerud 2007).
Audio guidance included • Works on all devices
The Norwegian 4×4 protocol is a high-intensity interval training (HIIT) method developed by researchers at the Norwegian University of Science and Technology. It was originally designed to improve cardiovascular fitness in cardiac rehabilitation patients but has since been adopted by elite endurance athletes worldwide.
Peer-reviewed studies show this protocol raises VO2max (maximum oxygen uptake) more than traditional steady-state cardio — about 10% over 8 weeks in trained runners (Helgerud 2007), with larger relative gains in less-trained and clinical populations.
Originally developed for cardiac patients, it's proven safe and effective for improving heart function, blood pressure, and overall cardiovascular health.
In about 40 minutes, 2-3 times per week — 16 of those minutes at hard effort — you can achieve better results than hours of traditional cardio training.
Works with any cardio activity: running, cycling, rowing, swimming, elliptical, or even walking uphill. Choose what works for you!
Start with light cardio to gradually increase your heart rate and prepare your body.
Work at 90-95% of your maximum heart rate (85–95% is also commonly prescribed). You should be breathing hard and unable to hold a conversation.
Reduce intensity to 60-70% max HR. Keep moving but allow your heart rate to come down.
Complete 4 work intervals with 3 recovery periods between them.
Finish with light activity and stretching to help your body recover.
The Norwegian 4×4 protocol is anchored to 90–95% of your maximum heart rate during work intervals (the original Helgerud 2007 protocol; 85–95% is also commonly prescribed). Hitting the right zone is the single biggest factor in whether you actually drive VO2max adaptations.
Use the Tanaka formula — it is more accurate than the older 220 − age rule, especially for adults over 40:
Max HR ≈ 208 − (0.7 × age)
Example for a 35-year-old: 208 − (0.7 × 35) = 184 bpm. The 4×4 work zone (90–95%) is then 166–175 bpm.
Don't have a heart rate monitor? Use perceived exertion: during the 4-minute work interval you should rate the effort 8–9 out of 10 — breathing hard, unable to hold a conversation, but not all-out sprinting.
Both are high-intensity interval workouts but they target different adaptations:
| Norwegian 4×4 | Tabata | |
|---|---|---|
| Work interval | 4 min @ 90–95% max HR | 20 s all-out |
| Rest interval | 3 min active | 10 s passive |
| Total work time | 16 min | 4 min |
| Session length | ~40 min | ~10 min |
| Primary adaptation | VO2max, aerobic capacity | Anaerobic power, sprint capacity |
| Beginner friendly | Yes (with HR scaling) | No — extreme intensity |
For pure cardiovascular fitness and endurance, the Norwegian 4×4 has more peer-reviewed evidence. Tabata is excellent supplemental work for athletes who already have an aerobic base.
The 4×4 was originally developed for cardiac rehabilitation, so it scales down well. If you are new to HIIT, modify the standard protocol like this for your first 2–3 weeks:
Progress one interval per week until you reach the full 4×4 at full intensity.
The protocol is modality-agnostic — pick the activity you can sustain at the right heart rate zone:
The Norwegian 4×4 was studied extensively at the Norwegian University of Science and Technology (NTNU) in Trondheim. In a Circulation 2008 pilot study of 32 metabolic-syndrome patients, Tjønna et al. measured a 35% VO2max rise with the 4×4 versus 16% with moderate continuous training over 16 weeks. In heart-failure patients (Wisløff et al., Circulation 2007, n=27), the 4×4 raised VO2peak 46% versus 14% for moderate training over 12 weeks.
Subsequent work by Helgerud, Wisløff, and others has replicated the findings in healthy adults, endurance athletes, and clinical populations. The protocol is now part of the standard cardiac rehabilitation toolbox in Norway and increasingly worldwide.
References: Tjønna AE, et al. Aerobic interval training versus continuous moderate exercise as a treatment for the metabolic syndrome. Circulation. 2008;118(4):346–354. Wisløff U, et al. Superior cardiovascular effect of aerobic interval training versus moderate continuous training in heart failure patients. Circulation. 2007;115(24):3086–3094. Helgerud J, et al. Aerobic high-intensity intervals improve VO2max more than moderate training. Med Sci Sports Exerc. 2007;39(4):665–671.
The Norwegian 4×4 is a high-intensity interval training method developed at the Norwegian University of Science and Technology (NTNU). It consists of four 4-minute intervals at 90–95% of maximum heart rate (85–95% is also commonly prescribed), separated by three 3-minute active recovery periods at 60–70% max HR. A full session runs about 40 minutes: a 10-minute warm-up, 16 minutes of hard intervals with recoveries between them, and a cool-down.
Most studies use 2–3 sessions per week with at least 48 hours between sessions. Two sessions per week is enough to drive significant VO2max improvements; three is the upper end before recovery becomes the limiting factor.
Use the Tanaka formula: 208 − (0.7 × age). It is more accurate than the older 220 − age estimate. For example, a 35-year-old has an estimated max HR of 184 bpm, so the 90–95% work target is 166–175 bpm. The most accurate method is a supervised graded exercise test.
No. The protocol works with running, cycling, rowing, swimming, the elliptical, stair-climbing, or even walking uphill. A heart rate monitor is recommended but not required — perceived exertion (RPE 8–9 out of 10 during work intervals) works as a proxy.
They target different adaptations. Norwegian 4×4 (16 minutes total work) is built for VO2max and aerobic capacity and is well-tolerated by most fitness levels. Tabata (4 minutes total work, 20s on / 10s off) is much shorter and more anaerobic — superior for sprint power but less effective for endurance VO2max gains. For cardiovascular fitness, the 4×4 has more peer-reviewed support.
Yes, with modifications. The protocol was originally developed for cardiac rehabilitation patients. Beginners should start at 80–85% max HR rather than 90–95%, choose low-impact modes like cycling or walking uphill, and reduce to 2 or 3 work intervals for the first 2–3 weeks. Always consult a doctor before high-intensity exercise if you have cardiovascular risk factors.
Calorie burn depends heavily on your body weight, modality, and effort, so we don't show a single figure that would be wrong for most people. The lasting benefit is the EPOC (excess post-exercise oxygen consumption) effect — your metabolism stays elevated for several hours after a hard 4×4 session.