The Best Norwegian 4x4 Apps for iPhone

Updated October 2026 · Feature claims verified against App Store listings. Reviewed quarterly.

Every app below can time a Norwegian 4x4: 4 minutes hard, 3 minutes easy, four rounds. The differences show up in what they can tell you afterward — live heart rate, per-interval analysis, and whether your heart rate recovery is improving. Here's the honest breakdown, ourselves included.

Which Norwegian 4x4 app should you use?

  • Best for tracking heart rate recovery: Viking 4x4. The only app here that measures 60-second recovery after every interval and trends it across sessions.
  • Best free all-rounder: N4x4. Watch app, broad sensor support, reminders, and streaks with no subscription.
  • Best minimal free timer: Boreas. Clean, simple, basic Watch heart rate.

Viking 4x4

Price
First 4x4 free, then $6.99/mo or $29.99/yr
Apple Watch live heart rate
Yes — Watch app auto-launches
Other heart rate sensors
Via Apple Health
Per-interval report
Peak HR, HR at +60s, HRR-60
60-second HR recovery (HRR-60) per interval
Yes
Recovery trend across sessions
Recovery Score (last 12 sessions)
Reminders & streaks
No
Voice coaching
Yes
Apple Health sync
Yes

N4x4

Price
Free (no subscription)
Apple Watch live heart rate
Yes — Watch app
Other heart rate sensors
AirPods Pro 3, Garmin, WHOOP, Polar, chest straps
Per-interval report
Zone chart, time in zone, time to zone
60-second HR recovery (HRR-60) per interval
No
Recovery trend across sessions
Last session overlay; VO2 max trend from Health
Reminders & streaks
Yes
Voice coaching
Yes
Apple Health sync
Yes

Boreas

Price
Free
Apple Watch live heart rate
Yes (basic)
Other heart rate sensors
No
Per-interval report
No
60-second HR recovery (HRR-60) per interval
No
Recovery trend across sessions
No
Reminders & streaks
No
Voice coaching
Interval cues
Apple Health sync
Yes

Norwegian 4x4 Protocol

Price
$5.99
Apple Watch live heart rate
No
Other heart rate sensors
No
Per-interval report
No
60-second HR recovery (HRR-60) per interval
No
Recovery trend across sessions
Basic log
Reminders & streaks
No
Voice coaching
Timer alerts
Apple Health sync
Partial

Generic HIIT timers

Price
Free–$10
Apple Watch live heart rate
Varies
Other heart rate sensors
Varies
Per-interval report
No
60-second HR recovery (HRR-60) per interval
No
Recovery trend across sessions
No
Reminders & streaks
Varies
Voice coaching
Varies
Apple Health sync
Varies

Feature comparison as of October 2026. "Varies" reflects a category of apps rather than a single product.

Viking 4x4Our app

The one built around heart rate recovery. After every interval it measures how far your heart rate falls in 60 seconds (HRR-60), rates the session from Low to Elite, and charts a Recovery Score across your last 12 sessions — the most direct read on whether your heart is adapting. Free to download with your first full session free; unlimited training is a paid subscription. It doesn't do reminders or streaks yet.

N4x4

The strongest free option, and we'll say so plainly: broad sensor support, a Watch app, reminders, streaks, a Lock Screen Live Activity, and per-interval zone charts — with no subscription. Its listing doesn't describe 60-second heart rate recovery. If you want the most features for free, start here; if you want recovery as your progress metric, that's Viking 4x4's lane.

Boreas

A clean, solid free timer with basic Apple Watch heart rate, zone display, calories, and Health saving (4.8 stars). It times the protocol well; it doesn't analyze intervals or track recovery.

Norwegian 4x4 Protocol

A paid timer with basic session tracking, best known for a Tim Ferriss blog mention. No live heart rate analytics or recovery measurement.

Generic HIIT timers

For apps like HIIT Timer or VO2Max Timer, the 4x4 is one preset among many. Fine for casual use; none are built around the protocol or its physiology.

The honest bottom line: there are good free 4x4 apps now, and N4x4 is the most complete of them. Viking 4x4 is for people who want one specific answer — is my heart actually getting fitter? — measured the way cardiologists read it: how fast your heart rate falls after hard effort. If that's why you're doing the 4x4 to raise your VO2 max, your first full session is free.

SKÅL!

The 4x4 app that shows your heart getting stronger.

Download on theApp StoreFree download · First 4x4 free

Your first 4x4 is free · iPhone · Apple Watch companion