The Norwegian 4×4 Interval Method

If you’ve ever heard someone say “the best cardio is the one you’ll actually do,” the Norwegian 4×4 is a strong contender. It’s simple, repeatable, time-efficient, and—when done correctly—very effective at improving VO₂max (your body’s ability to use oxygen at high effort), a key marker of aerobic fitness.

Here, I’ll cover:

• where the 4×4 came from (and what’s myth vs reality),
• exactly what it is,
• how to do it correctly,
• and what research shows it can improve.

---

A quick history of interval training:

Intervals have been used for generations in endurance sports. What researchers at the Norwegian University of Science and Technology and the Cardiac Exercise Research Group did was standardize a very usable version—4 minutes hard, 3 minutes easy, repeated 4 times—and then study it extensively in athletes and clinical populations.

NTNU’s CERG group has published widely on interval-based training and helped popularize the 4×4 format in performance and rehabilitation settings. They also emphasize that 4×4 isn’t uniquely Norwegian, but the “Norwegian Protocol” label stuck because it was so strongly promoted and studied there. (Norwegian SciTech News)

---

What is the Norwegian 4×4?

At its core, the 4×4 is a high-intensity interval training (HIIT) session designed to keep you near a very high aerobic demand long enough to trigger adaptation—without going all-out from start to finish.

NTNU’s CERG outlines it like this:

• Warm-up: ~10 minutes at 60–70% HRmax
• Intervals: 4 × 4 minutes at 85–95% HRmax
• Active recovery: 3 minutes at 60–70% HRmax between intervals
• Cool down: ~5 minutes easy (NTNU)

Total time: usually 35–40 minutes including warm-up and cool down.

---

Why 4 minutes? Why 4 rounds?

Four-minute work bouts are long enough for most people to reach near-maximal oxygen uptake during each interval. Repeating them four times provides enough total “quality time” at high oxygen demand to drive improvements in aerobic capacity.

This is one reason the 4×4 format appears frequently in HIIT research: it reliably places people in the target intensity range (85–95% HRmax) for a meaningful duration. (PMC)

---

How to do the Norwegian 4×4 correctly

1) Pick the right “tool”

Choose a modality where you can hold steady effort and control intensity:

• treadmill (incline helps),
• bike/air bike,
• rower,
• running outdoors (best if you have a track or proof of pacing),
• stairmill.

If you’re new to intervals, bike/rower often feels safer on joints than sprinting.

2) Warm up like you mean it

Do 8–12 minutes easy, then add 2–3 short “pickups” (10–20 seconds) to prepare your heart and legs. CERG’s warm-up guidance sits around 60–70% HRmax. (NTNU)

3) The intervals (the part people mess up)

You want “hard but controlled.” Two common ways to hit it:

Heart-rate method (best if you have a monitor):

• Aim to spend most of each 4-min interval around 85–95% HRmax. (NTNU)
  Because HR lags, it’s normal to reach the top end in minute 2–3.

Effort method (works without tech):

• RPE ~8/10: heavy breathing, can’t talk, but you can maintain it for the full 4 minutes without crashing.

4) Recovery (don’t stop moving)

Active recovery means easy movement, not standing still. The goal is to drop intensity while staying warm and ready for the next repeat—again around 60–70% HRmax in CERG’s outline. (NTNU)

5) Cool down

5–10 minutes easy.

---

Common mistakes (and how to fix them)

Mistake #1: Going too hard on interval 1
If interval #4 is a survival shuffle, you sprinted the first rep. The goal is repeatable power.

Fix: pick a pace you can hold for all four rounds, then progress gradually.

Mistake #2: Recovering too much (or not enough)
If you stop completely, your legs tighten and pacing falls apart. If you recover too hard, interval quality drops.

Fix: keep recovery truly easy, but moving.

Mistake #3: Doing it too often
4×4 is potent. Many people progress faster doing it 1–2 times/week consistently than doing it 4 times/week for two weeks… then quitting.

---

How often should you do 4×4?

For most people:

• 1–2 sessions per week is plenty when combined with easier Zone 2 work and strength training.
• If you’re already conditioned and recovering well, some plans use 2–3 times/week blocks—but volume and life stress matter.

HIIT reviews in clinical and general populations frequently include the 4×4 format and show it can improve aerobic capacity efficiently, but it’s typically programmed with recovery and moderation in mind. (PMC)

---

The evidence-based benefits (what we actually know)

1) Increases VO₂max effectively

A landmark treadmill study comparing training intensities found that high-intensity interval training improved VO₂max significantly, with a 4×4-minute interval group showing meaningful gains over the training period. (PubMed)

2) Improves central cardiovascular function (e.g., stroke volume)

In that same line of work, interval training produced improvements consistent with better cardiac pumping capacity (including stroke volume changes in the interval groups). (PubMed)

3) Strong results in cardiac rehabilitation research (when appropriately supervised)

The 4×4 format has been tested in clinical populations, including:

• Coronary artery disease (CAD): high-intensity interval work was reported superior to moderate training for improving aerobic capacity in a controlled trial. (PubMed)
• Heart failure: a randomized Circulation study reported stronger cardiovascular effects from aerobic interval training than moderate continuous training. (PubMed)
• Reviews note that the 4×4 protocol is commonly used in cardiac populations and often compares favorably to moderate training for improving VO₂peak. (PMC)

Important note: these outcomes depend on screening, appropriate intensity prescription, and supervision when needed—especially in higher-risk groups.

4) It’s time-efficient

You get 16 minutes of true hard work plus warm-up/cool-down. That’s appealing for busy schedules—and one reason the method has spread widely beyond Norway. (NTNU)

---

Who should be cautious (and how to scale it safely)

CERG’s own guidance is clear: interval training should not be “run until you drop,” and people with known disease risk or uncertainty should consider medical input and, when appropriate, exercise testing. (NTNU)

Beginner-friendly ramp (2–4 weeks)

If you’re not used to high-intensity work:

• Start with 3×3 minutes at a controlled hard effort, 2–3 minutes easy between
• Or do 4×2 minutes hard / 2 minutes easy
• Then build toward the full 4×4

---

The bottom line

The Norwegian 4×4 is popular because it hits a sweet spot:

• long enough intervals to drive VO₂max improvements,
• structured recovery to keep quality high,
• simple enough to repeat for months.

Do it hard but controlled, 1–2 times per week, and pair it with easy aerobic work and strength training for a complete program.

---

References

• CERG/NTNU: protocol description and intensity targets (warm-up, 4×4 at 85–95% HRmax, active recovery at 60–70%). (NTNU)
• Helgerud et al. (2007): high-intensity aerobic intervals (including 4×4) improved VO₂max and cardiovascular measures vs other intensity models. (PubMed)
• Rognmo et al. (2004): CAD trial reporting high-intensity interval exercise superior to moderate intensity for aerobic capacity outcomes. (PubMed)
• Wisløff et al. (2007, Circulation): aerobic interval training vs moderate training in heart failure patients. (PubMed)
• Acala et al. (2020): characterizing HR response to the 4×4 protocol (85–95% HRmax target commonly used). (PMC)
• Ito (2019) review: 4×4 frequently used in CAD/CHF research with favorable outcomes vs moderate training in many studies. (PMC)
• NTNU Norwegian SciTech News (2024): context on popularity, history, and ongoing debate around 4×4 claims. (Norwegian SciTech News)