Norwegian 4x4 workout

Live heart-rate zone coaching for every interval, with your Apple Watch or any Bluetooth monitor. First workout free, then a one-time purchase. No subscription.

Focus on your effort. The app does the rest.

Norwegian 4×4 is a guided interval workout that calculates your target heart-rate zone, runs the interval timer, and, with an Apple Watch or Bluetooth heart rate monitor, prompts you to stay in zone through every interval. You focus on the workout. It guides you though the protocol.

The workout is simple and always the same shape: warm up (customize length), then four hard 4-minute intervals with 3 minutes recovery between them, then cool down. You always know how hard to push and how much time is left.

What you get

• Live zone coaching with an Apple Watch or Bluetooth heart rate monitor: push harder, in the zone, or reduce effort, updated every second
• A clean guided timer for the full 4×4 session
• After each workout: heart-rate recovery, peak heart rate, and time in zone
• A fitness trend that follows your recovery over recent sessions, so you can see progress
• Haptic and sound cues on every phase and zone change, so you can train without watching your wrist
• Run the whole session from your Apple Watch, no phone needed
• Connect any Bluetooth heart rate monitor: Garmin DualHRM, Whoop band, and more.

Records to Apple Health Pick your activity and each session saves to Apple Health as that workout type. Workouts recorded on your Apple Watch count toward your rings, and you can review every session in the app's history.

Evidence-based The Norwegian 4×4 is one of the most studied interval workouts for building aerobic fitness. The app calculates your zones from your age or a heart rate you set yourself.

Private by design No account. No ads. No analytics. Nothing leaves your device.

One price, no subscription Your first workout is free. After that it is a one-time $4.99 purchase. No subscription, ever.

Requirements Heart-rate tracking and zone coaching require an Apple Watch or Bluetooth heart rate monitor. On iPhone alone, the app runs as a guided interval timer.