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.

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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.

    Privacy practices may vary, for example, based on the features you use or your age. Learn More

    The developer has not yet indicated which accessibility features this app supports. Learn More

    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.
    Languages
    English and 3 more
    • English, German, Polish, Spanish
    Age Rating
    4+
    Copyright
    • © 2026 Misty Logic