Crescendo 4×4 Support

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What is the Norwegian 4×4?: A research-backed interval protocol: four 4-minute pushes at 85–95% of your maximum heart rate, with 3-minute recoveries between them. It’s one of the most effective known ways to build VO₂max — and one of the hardest to start cold. That’s the problem Crescendo solves.
How does the on-ramp work?: You start at whatever level fits you — down to 30-second intervals — and each level slightly extends the work phase. Complete a few sessions at a level and you earn the next one, until you reach the full 4×4. You pick your starting level during setup and can change your level any time in Settings.
Do I need an Apple Watch?: No. The full experience runs on iPhone with voice guidance. If you do have a Watch, you can send any session to it and run it from the native Workout app with heart-rate targets on your wrist.
Do I need to connect Apple Health?: No — it’s optional. Health connection personalizes your heart-rate zones from your real data; without it, you enter your max heart rate manually (or accept the age-based estimate).
Will the voice cues work with the screen locked?: Yes. Cues keep firing with the screen locked, and they duck (not stop) your music or podcast.
Is Crescendo 4×4 free?: Yes — free, with no ads, no account, and no subscription.
Is this safe for me?: High-intensity interval training is demanding by design. If you’re unsure about your health, check with your doctor before starting — and start at the bottom of the on-ramp; that’s what it’s for.
Is my data private?: Yes. No account, no tracking, no server. Health data is read and written only with your permission and stays on your device. See the privacy policy.
I found a bug / have a suggestion.: Please tell us. Solo studio, but every message is read. Send a message.