Crescendo 4x4: Norwegian HIIT
VO2 max interval timer, 30 sec
Only for iPhone
Free · Designed for iPhone. Not verified for macOS.
iPhone
The Norwegian 4×4 protocol builds VO₂max like almost nothing else — four 4-minute pushes at 85–95% of max heart rate. The problem? Starting there feels like hitting a wall.
Crescendo removes the wall. You start with intervals as short as 30 seconds and climb a structured on-ramp, level by level, until the full 4×4 is yours. Progress is earned, never rushed — the app can even gently hold a level-up if your recovery data suggests you need it.
GUIDED SESSIONS
• Voice cues for every phase — works with the screen locked, music keeps playing
• Warm-up, four work/recovery cycles, cool-down: fully guided
• Date-anchored timing that never drifts
PERSONAL BY DESIGN
• Heart-rate zones from your real max HR — from Apple Health or set manually
• A conservative level-up gate that watches your resting HR and VO₂max trends
• Start where YOU are: from 30-second familiarization runs to the full protocol
APPLE WATCH + HEALTH
• Send any session to your Watch and run it from the native Workout app
• Watch-run sessions count toward your progress automatically
• Phone sessions save to Apple Health (your choice)
HONEST BY DEFAULT
• No account. No ads. No streak guilt.
• Your health data stays in Apple Health — we don't collect it.
High-intensity interval training is demanding. If you're unsure about your health, check with your doctor before starting.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
Your session now lives on the Lock Screen.
Start a workout and Crescendo appears on the Lock Screen and in the Dynamic Island — current phase, interval, target zone, and a countdown that stays right whether the app is open or not. Pause in the app and it holds. Finish or stop, and it clears itself.
Also in this release:
• The main Today buttons no longer shrink to unreadable text at large accessibility sizes — they wrap instead.
• If an update moves you up a level, the app now says so instead of doing it quietly.
• Translation fixes.
The developer, KRZYSZTOF ANDRZEJ OTRZASEK, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- KRZYSZTOF ANDRZEJ OTRZASEK
- Size
- 3 MB
- Category
- Health & Fitness
- Compatibility
Requires iOS 17.0 or later.
- iPhone
Requires iOS 17.0 or later. - Mac
Requires macOS 14.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
English and 3 more
- English, German, Polish, Spanish
- Age Rating
4+
- 4+
- Copyright
- © 2026 Misty Logic
