Your Elite HIIT Coach.
In Your Pocket.
4 rounds. Real-time heart rate coaching.
The scientifically-proven Norwegian 4×4 method—simplified.
Works seamlessly with Apple Health
HIIT is powerful.
But doing it right is hard.
Timing is everything
Constantly checking your watch breaks your flow
Which zone am I in?
Knowing whether to push harder or ease off is key
Progress lost
No tracking means no improvement
Meet your coach.
Always watching. Never judging.
You're in the zone
Glance at your phone. Instant feedback. Push harder or ease off—you always know.
Lock it. Pocket it. Keep going.
All your metrics on the lock screen. Switch to music. Take a call. Your coach keeps tracking.
See your transformation
Every workout saved to Apple Health. Watch yourself improve, week after week.
Trusted by elite athletes.
Validated by science.
The Norwegian 4×4 method: 4 rounds of 4-minute high-intensity intervals at 85-95% max heart rate, separated by 3-minute recovery periods.
Designed to maximize cardiovascular adaptation in under 50 minutes.
Three steps to elite fitness.
Enter your age
We calculate your personalized heart rate zones
Connect your Heart Rate Monitor
Real-time monitoring begins
Press start
Perfect every interval, stay in the right zone
Your data.
Your device.
Every heart rate reading, every workout—it all stays on your iPhone.
No cloud. No selling your information.
Read our privacy commitment →Ready to transform your fitness?
Download Norwegian 4×4 Trainer and start your first workout today.
Download on the App Store