Key takeaways
The session is 4 × 4 minutes at 90 to 95% of max heart rate with 3 minutes of active recovery, about 40 minutes total
In Helgerud 2007, 4×4 training raised VO2max by about 7.2% in eight weeks; steady groups did not change significantly
Once a week is enough for most people; expect noticeable change in 6 to 8 weeks
4 × 4 minutes hard, 3 minutes easy in between. Developed and studied by researchers in Trondheim, Norway, it is one of the best-researched sessions for raising VO2max, used by everyone from heart patients to elite athletes.
The research
- Helgerud et al., 2007: 40 moderately trained men trained three times a week for eight weeks with one of four programmes matched for total work: long slow running, threshold running, 15/15-second intervals, or 4×4 minutes at 90–95% of maximum heart rate. Only the two interval groups improved VO2max — by about 5.5% (15/15) and 7.2% (4×4) — alongside a rise in stroke volume. The steady groups didn't change significantly.
- Wisløff et al., 2007: in patients with heart failure after a heart attack, supervised 4×4 training on a treadmill improved peak oxygen uptake and heart function much more than moderate continuous training. (Patients trained under medical supervision.)
The session
- Warm up 10–15 min easy, finishing near the work intensity.
- 4 × 4 min at 90–95% of max heart rate. Heart rate lags: it should reach the zone by minute 2–3. Breathing is hard; you can say a few words, not sentences. Effort ≈ 8–9 out of 10.
- 3 min active recovery between reps at about 70% of max: jog or walk briskly. Keeping moving clears lactate and keeps heart rate up; standing still makes the next rep harder.
- Cool down 5–10 min easy.
Total: about 40 minutes.
Pacing it right
- The last rep should be the hardest but the same speed as the first. If you can't finish rep 4, you started too fast.
- For runners, 90–95% HRmax is roughly the pace you could race for 10–20 minutes — faster than threshold pace.
- On a treadmill, a 1–2% incline mimics outdoor effort; uphill reps outdoors are kinder on the legs.
- Heat and fatigue push heart rate up: on a hot day, run by heart rate or perceived effort, not pace.
How often
- Once a week for most people, twice for trained athletes in a VO2max-focused block.
- Keep the rest of the week mostly easy: see 80/20 training.
- Expect noticeable change in 6–8 weeks, if you recover well (resting heart rate, HRV and recovery).
How to progress
Track the same session over weeks. If heart rate in rep 4 is lower than before at the same speed, or the same heart rate comes at a higher speed, you're fitter. Then raise the speed slightly (e.g. +0.2–0.5 km/h) or the incline. Variations for advanced athletes: 5×4, 6×3 or 5×5 minutes.
Safety: if you have a heart condition, high blood pressure, or have been inactive, get medical advice before hard intervals.
Frequently asked questions
What is the Norwegian 4×4 workout?
It is four 4-minute intervals at 90 to 95% of your maximum heart rate, with 3 minutes of easy jogging or brisk walking between them. With a warm-up and cool-down it takes about 40 minutes.
How often should I do 4×4 intervals?
Once a week for most people, or twice for trained athletes in a block focused on VO2max. Keep the rest of the week mostly easy so you recover well.
How hard should 4×4 intervals feel?
Hard: about 8 to 9 out of 10, breathing heavily and able to say only a few words. The last rep should be the hardest but run at the same speed as the first; if you cannot finish rep 4, you started too fast.
Sources
- Helgerud J, et al. Aerobic high-intensity intervals improve VO2max more than moderate training. Med Sci Sports Exerc, 2007.
- Wisløff U, et al. Superior cardiovascular effect of aerobic interval training versus moderate continuous training in heart failure patients: a randomized study. Circulation, 2007.