Dan's Newest Favorite Workout - Norweigian 4x4s

I have a new favorite workout.

Norwegian 4x4s.

It’s a simple interval protocol:

4 rounds of:

• 4 minutes hard (about 85–95% of max heart rate)

• 3 minutes easy recovery
  
  

I’ve been doing two Norwegian-style interval sessions per week since October and I feel awesome.

These workouts take me 30–40 minutes total (warm-up + cool-down included) and I don’t feel totally wrecked afterwards.

If anything - I feel energized.

What the research says Norwegian 4x4s can do:

1) Raise VO₂ max - fast.
The NTNU crew (the Norwegians who popularized this) found 4x4-style intervals improved VO₂ max more than steady “long slow distance” or threshold work in about 8 weeks. In broader HIIT research, intervals often match or beat steady cardio for VO₂ max - with less total time.

2) Make your heart a stronger pump.
Intervals don’t just make you feel fit. They can improve stroke volume (how much blood your heart pumps per beat). In some studies - even in clinical populations like heart failure - interval training improved VO₂ peak and heart function measures more than moderate steady work.

3) Improve metabolic health.
In overweight adults and people with metabolic syndrome, aerobic intervals improved fitness and moved risk markers in the right direction. Same calorie burn, better results. The variable wasn’t “more work” - it was intensity.

4) Upgrade blood vessel function.
HIIT has been shown to improve vascular function (how well your arteries respond and dilate). Better blood flow, better delivery, better system performance.

5) Hard… but repeatable (which is why it works).
4x4 isn’t a death sprint. It’s controlled intensity. You spend real time in that 85–95% zone - breathing hard, focused, but not redlining. Hard enough to trigger adaptation, controlled enough to do it again next week.

This is how you build a foundation that supports everything else: Rucking, strength, adventure, and longevity.

How to start Norwegian 4x4s (without getting hurt):

The biggest mistake with 4x4s is treating them like a test.

They’re not a test. They’re training.

The goal is a hard but repeatable effort - not cardio that takes you to the shadow realm.

If you’re still getting back in shape, or trying intervals for the first time -here’s the safest way to start:

Step 2: 2-week on-ramp (2x/week)
Warm up: 10 minutes easy.
Then 6 rounds of 1 minute hard + 2 minutes easy.
Cool down: 5–10 minutes easy.
“Hard” means you’re breathing heavy, but your form stays tight.
You should finish thinking: I could do more… but I won’t.
This is the way.

Step 3: 4x4 “Lite” (next 2–3 weeks)
Warm up: 10–15 minutes easy.
Then 4 rounds of 3 minutes hard + 3 minutes easy.
Cool down: 5–10 minutes easy.
The first interval should feel almost too easy.
If you blow up in round 2, you went too hard.

Step 4: Full Norwegian 4x4
Warm up: 10–15 minutes easy.
Then 4 rounds of 4 minutes hard + 3 minutes easy.
Cool down: 5–10 minutes easy.
Intensity cue (no heart rate monitor needed): during the 4 minutes you can only speak 3–5 words at a time.
Not a full-on sprint.
A controlled effort you can repeat next week.

Simple rules so you don’t get wrecked:

Max 2x/week. More isn’t better. Better is better.

Increase one thing at a time (speed OR incline OR duration - not all three).

If something hurts, change the tool (bike instead of run) - don’t quit the habit.

Recovery is the metric. If you’re trashed for 72 hours, it’s too much.

Play the long game.

We start a new training block next week on the Wild Gym app, and it includes an optional Norwegian 4x4 progression.

This is a great opportunity to build a habit that moves the needle on your energy, your fitness, and your longevity.

But you’ve gotta start slow… and commit to the long-term.

P.S. If you’re Norwegian 4x4 curious, check out the Wild Gym App. There’s a no-obligation 14-day trial, and you can cancel anytime.