4x4 HIIT vs Intervalla

Transform your cardiovascular fitness with the Norwegian 4x4 HIIT protocol - the scientifically-backed method used by elite athletes and researchers to dramatically improve VO2 max and heart health. WHAT IS 4x4? Four intervals of 4 minutes at high intensity (85-95% max heart rate), separated by 3 minutes of active recovery. That's it. WHY IT WORKS Developed by Norwegian exercise scientists, this protocol has been proven in clinical studies to: - Increase VO2 max faster than traditional cardio - Improve cardiovascular health - Boost endurance and athletic performance - Deliver maximum results in minimum time SIMPLE TO USE - Clear visual timer with audio cues - Tracks your intervals automatically - Works with any activity: running, cycling, rowing, or body weight exercises - No complicated setup - just hit start PERFECT FOR - Runners looking to improve race times - Athletes building aerobic capacity - Anyone wanting efficient, science-backed cardio - People with limited time for training The Norwegian 4x4 protocol is one of the most researched and effective HIIT methods available. Stop guessing. Start training with proven science. Download now and take the first step toward your best cardiovascular fitness.

Free. No ads. No account required. Intervalla is a precision interval timer built for serious training. Whether you follow the classic Tabata protocol, push through an AMRAP session, or design your own custom intervals — this app keeps you on pace with a clean, distraction-free interface. THREE TRAINING MODES • Tabata — 20s work / 10s rest with configurable rounds • AMRAP — As many reps as possible in one timed block • Custom — Set your own work, rest, rounds, warm-up and cool-down LIVE HEART RATE Connect any Bluetooth Low Energy heart rate monitor (Polar, Garmin, Wahoo, etc.) and see your BPM in real-time. Switch to HR mode for a live sparkline graph that tracks your intensity throughout the session. After your workout, get a full summary with avg/max/min BPM and time in each heart rate zone. WORKS WITH YOUR SCREEN LOCKED Put your phone in your pocket and train. Audio cues play reliably in the background, and your heart rate monitor stays connected — even with the screen off. DESIGNED FOR FOCUS • Circular progress ring with phase-specific colors • Distinct audio cues for work, rest, and transitions • Lock controls to prevent accidental taps mid-workout • Dark interface that's easy to read mid-workout SAVE YOUR FAVORITES Save up to 5 custom presets and start any workout with a single tap. Three built-in presets included to get you started immediately. AUDIO THAT WORKS Plays through the silent switch on iOS — never miss a cue. Different tones for work start, rest start, countdown, and workout complete. SHARE WORKOUTS Create a workout and share it with friends, training partners, or your community. One link opens a ready-to-run timer. COMPLETELY FREE No ads, no subscriptions, no account required. Just open and train. Built with care in Norway.