How fast to run a 4x4: slower than you think
For most runners the center of the 4x4 pace band lands on their 10K race pace, and 5K race pace is the ceiling, not the target. Advice to run 4x4s "at 5K pace" or "at interval pace" puts you at the top of the band or beyond it for four minutes at a time.
The calculator starts from your race time. It converts it to VDOT (Jack Daniels' fitness score) and sets the work pace at 90–95% of the speed that VDOT predicts at VO2max, with 92.5% as the center. That band is our mapping, not a number from the original study, which trained on an inclined treadmill and reported heart rates, not speeds.
| Recent 10K | 4x4 range /km | Center /km | Your 5K pace |
|---|---|---|---|
| 60:00 (6:00/km) | 6:04–5:45 | 5:54 | 5:46 |
| 50:00 (5:00/km) | 5:06–4:50 | 4:58 | 4:49 |
| 41:20 (4:08/km) | 4:16–4:02 | 4:09 | 3:59 |
The center equals a pace you could hold for about 44 minutes in a race. So for a 50-minute 10K runner it sits right on 10K pace, and for a 60-minute 10K runner it is a little faster than 10K pace. Expect individual differences of roughly 3% of speed (our estimate, about 10 seconds per km), so heart rate has the final say.
The original 4x4 study and what it found
The 4x4 comes from a 2007 study by Jan Helgerud and colleagues at the Norwegian University of Science and Technology (NTNU), published in Medicine & Science in Sports & Exercise. The prescription:
- Work: 4 intervals of 4 minutes at 90–95% of maximum heart rate.
- Recovery: 3 minutes of active recovery at about 70% of max between intervals, moving rather than standing still.
- Dose: 3 sessions a week for 8 weeks.
The 40 subjects were healthy, moderately trained men, not a group of runners, split into four training groups doing the same total work. In the 4x4 group, VO2max rose from 55.5 to 60.4 ml/kg/min on average. The two interval groups (4x4 and 15 seconds on, 15 seconds off) improved VO2max more than steady running at 70% or 85% of max heart rate.
NTNU's public advice today is broader and counts 85–95% of max heart rate as on target; the result card shows that 85% floor. Figures such as "27 patients" or "+46%" that circulate with the 4x4 come from a different trial: Ulrik Wisløff's 2007 study of heart-failure patients.
Why the first interval feels wrong: heart-rate lag
Heart rate climbs more slowly than effort. In the first 4-minute interval it can take most of the rep to reach 90% of max, so runners who chase the number go out too hard, or decide the workout is not working.
- Start the clock with the effort. Do not wait for your heart rate before timing the 4 minutes. In the original study, participants were told to reach target intensity within 1–1.5 minutes and then adjust speed to hold it.
- Use pace for the first 1–1.5 minutes. Run near the fast end of your band, then settle to the center.
- Judge rep 1 by its end. NTNU counts the first interval as on target if you reach 90% within its 4 minutes; later intervals should get there within 1–2 minutes.
- Check at minute 3. Above 95% of max? Ease off 5–10 seconds per km. Still under 90% from the second interval on? Speed up a little.
Intervals 3 and 4 usually need a slightly slower pace to stay in the same heart-rate zone, because heart rate drifts upward (in a cycling study of the 4x4, riders had to keep lowering their effort from interval to interval to stay in the zone). At the end you should feel you could have done a fifth interval, which is how NTNU describes the right effort.
Get your max heart rate right first
Every heart-rate number on the card is a percentage of your max, so a wrong max shifts the whole workout. The calculator uses the HUNT formula, 211 - 0.64 × age, from a Norwegian study of 3,320 healthy adults (Nes and colleagues, 2013). For a 40-year-old that gives 185 bpm and a work zone of 167–176 bpm.
A formula gives an average. Its typical error is about 10.8 bpm, so many people's real max is 10 or more beats higher or lower. If you know your measured max, enter it and it replaces the formula.
- Test it in the field: after a thorough warm-up, run 3–4 hard minutes up a steady hill or on a treadmill and finish all-out; the highest reading is close to your max. Skip this if you have a heart condition or have not been cleared for hard exercise.
- Do not use a random peak: a number once seen on a climb, or a spike from a loose sensor, is not a tested max.
- Wear a chest strap for 4x4s: wrist optical sensors tend to lag behind a chest strap when intensity jumps, which is exactly what happens at the start of every interval.
4x4, Yasso 800s, the "Norwegian method" and "Norwegian HIIT" are different workouts
- Norwegian 4x4: 4 × 4 minutes at 90–95% of max heart rate with 3-minute active recoveries. A VO2max session of about 40 minutes with warm-up and cool-down.
- Yasso 800s: 10 × 800 m, each in your marathon goal time read as minutes:seconds, with equal-time jogs. A marathon-specific session that usually lands near 5K pace, faster than the 4x4 center. Get your times with the Yasso 800 calculator.
- The "Norwegian method": the double-threshold training linked to Marius Bakken and the Ingebrigtsen brothers, with two threshold sessions on the same day controlled by a lactate meter. The effort stays below what a 4x4 asks for. "Méthode norvégienne" in French running media usually means this.
- "Norwegian HIIT" with Tabata inside: some fitness-app and Japanese versions fill each 4 minutes with 20 seconds on and 10 seconds off. That is the Tabata format (8 rounds of 20/10), a different near-maximal workout; a 4x4 is one steady hard effort for the full 4 minutes.
If you already do one VO2max session a week, let the 4x4 replace it rather than add to it.
Treadmill, bike and incline walking
- Treadmill: set a 1% incline, which roughly makes up for the missing air resistance of running outside (Jones and Doust, 1996), and use the km/h or mph from the card. The original study also used a treadmill, at 5.3% incline, and did not report belt speeds, which is one more reason to treat the pace band as an estimate and heart rate as the check.
- Bike: go by heart rate only, since running paces do not transfer. Heart rate on a bike often tops out a few beats lower than when running, so raise the resistance until you reach the zone.
- Incline walking: a popular low-impact option. In online treadmill communities a common starting point is about 3–4 mph (5–6.5 km/h) at 8–12% incline, adjusted until heart rate reaches 90% of max. That range is shared experience, not a study figure.
Whatever the machine, the recovery stays the same: 3 minutes easy at about 70% of max, moving rather than stopped.