Norwegian 4x4 Interval Training: Structure, Intensity, and Safety
April 16, 2024
Reviewed September 2026.
Norwegian 4x4 interval training is a structured way to build aerobic fitness, developed and studied at the Norwegian University of Science and Technology.
Norwegian 4x4 training uses four hard intervals, each four minutes long, with three minutes of active recovery between them. NTNU's published version includes a gradual warm-up and a cool-down. The hard intervals are controlled, not all-out sprints.
What the Protocol Trains
The protocol is one way to train cardiorespiratory fitness. It asks for repeated hard aerobic efforts with active recovery, so the main training variable is the ability to sustain and repeat a demanding pace.
If you have a heart condition, blood-pressure concern, diabetes, concerning symptoms, or a long break from vigorous exercise, ask your healthcare professional whether this intensity is appropriate before trying it.
How to Do a Norwegian 4x4 Session
- Warm-Up: Before diving into your workout, spend a few minutes warming up your muscles with some light jogging, jumping jacks, or stretching.
- Interval Time: Get ready to alternate between four minutes of intense exercise (like boxing, kickboxing, sprinting or cycling as fast as you can, at least fast enough where you can’t talk while doing it) and three minutes of active recovery (like walking, core work or slow jogging).
- Repeat: Keep going with this pattern for 4 sets, pushing yourself during the intense intervals and taking it easy during the recovery periods.
- Cool Down: Once you’ve completed your last interval, take 10-15 minutes to cool down with some gentle stretching and deep breathing.
Start with two intervals and build to four over several weeks. Keep the hard efforts controlled and repeatable.
References:
- Weston, K. S., et al. (2014). “High-intensity interval training in patients with lifestyle-induced cardiometabolic disease: a systematic review and meta-analysis.” British Journal of Sports Medicine, 48(16), 1227-1234
- Tuomainen, P., et al. (2014). “Cardiorespiratory fitness and risk of type 2 diabetes: a population-based cohort study.” Diabetes Care, 37(8), 2288-2295
- Myers, J., et al. (2017). “Cardiorespiratory Fitness and Cardiovascular Disease: The Past, Present, and Future.” Journal of the American College of Cardiology, 69(7), 952-964
How Forge Uses the 4x4
Forge does not run the Norwegian 4x4 as a standalone class. The protocol is woven into some training days in Women's Only Kickboxing and Women's Only Strength & Kickboxing and in Co-Ed Kickboxing, where the round structure already fits four hard intervals with active recovery between them. Check the class schedule for current times.
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