Norwegian 4x4 Timer
Norwegian 4x4 Timer app icon

Train your VO2 max

A dead-simple iPhone interval timer for the Norwegian 4x4 protocol. Or any custom interval workout you want to build.

Coming soon to the App Store

Home screen showing warm-up, work, rest, interval, and cool-down settings above a workout timeline chart
Set it up once
Live workout screen with a countdown ring reading 3:58 remaining during work interval 1 of 4
Run the workout
Settings screen with sound and vibration toggles and separate transition sounds for work and rest
Pick your alerts

The app in a nutshell

Costimizable intervals

Warm-up, work, rest, cool-down, and the number of sets are all configurable, and they persist between launches.

Sound and vibration alerts

Alerts fire at every transition; even when the app is in the background or the screen is locked. Work and rest sets each get their own tone, so you know which phase is starting without looking.

Local-first privacy

Get started immediately with no sign-up or account required. Your settings and workout history stay completely private and local to your iPhone.