Intervals
Norwegian 4x4
The VO2max classic: 4 × 4 minutes hard.
Main set: 4 × (4 min @ 90% + 3 min @ 35%)
About this workout
The 4x4 was brought into Norwegian elite sport in the 1990s by Jan Helgerud and Jan Hoff at NTNU in Trondheim, which has studied it for years. The classic protocol is 4 intervals of 4 minutes at 85–95% of maximum heart rate with 3 minutes of active recovery. In a 2007 study, moderately trained men who did it 3 times a week for 8 weeks raised their VO2max by 7.2%, though a group doing 15/15 intervals improved almost as much.
It isn't the "Norwegian method" of threshold training, which is a different approach. Fartlek's version sets the reps at 90% effort with 3 easy minutes between them; once or twice a week is plenty. The 2007 study.
The workout
| Block | What to run | Cue |
|---|---|---|
| Warm-up | 2 min @ 30% + 2 min @ 40% + 2 min @ 50% + 1 min rest | Smooth jog with steady pickups |
| 4-minute intervals | 4 × (4 min @ 90% + 3 min @ 35%) | Hard but even — no fade on rep 4 |
| Cool-down | 2 min @ 30% | Ease down, breathe |
How each effort should feel
Efforts are a percentage of your all-out effort, set by feel (RPE), not by pace. From Fartlek's effort guide:
- 30% Very easy. Walking pace or the gentlest jog.
- 35%, 40% Easy. Relaxed jog, easy to chat.
- 50% Comfortable. Easy running, full sentences.
- 90% Very hard. A word or two, tops.
Pete's tip
Run each 4-minute effort at a pace you could hold for all four, breathing hard but controlled. Jog the recoveries, don't walk them. Even reps beat heroic first ones.
Pete, Fartlek's AI coach
What it trains
Stamina. Maintain intensity over sustained efforts.