Rhythm Experimental

Rhythm (experimental) — a picture of your beat-to-beat timing

Rhythm draws a picture of how regular your heart's beat-to-beat timing was during quiet rest — a Poincaré scatter plot with a few plain descriptive numbers. It works on every strap, including a WHOOP 4.0.

Read this first. Rhythm is a visualisation, not a verdict. It is not an ECG, not a diagnosis, not a medical device, and it cannot detect, rule out or monitor any heart condition. Variation in beat-to-beat timing is normal and often completely benign. It exists to show you your own data honestly, nothing more.

It's off by default and sits behind a consent screen you have to read and accept.

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Turning it on

1. Go to Settings → Rhythm.
2. Tap "Turn on Rhythm."
3. Read the "Before you turn on Rhythm" consent screen. It lays out, point by point, that this is experimental, will sometimes be wrong, that irregular timing is often benign, that it's not a substitute for a clinician, and that everything stays on your device.
4. Tick the single checkbox to confirm you understand, then accept. If you back out, Rhythm stays off and nothing is computed or stored.

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Reading the picture

After a quiet resting window (Rhythm only looks during stillness — movement is discarded, not flagged), the Rhythm screen shows:

• The beat-to-beat scatter — each point is one interval plotted against the next. A tight comet shape reads as steady; a diffuse, round cloud reads as more varied. You can literally see it.
• Descriptive stats — SD1, SD2, and the SD1:SD2 ratio (the long and short axes of that cloud), plus how many beats were read.
• A plain categorical read — one of:
  • Rhythm — steady ("Your rhythm looked steady")
  • Some occasional extra or skipped beats
  • Your rhythm varied more than usual
• A confidence line — e.g. "Building — one short window" — so a thin night reads truthfully.

No single window ever produces an alarm. There's no red, no urgency, no condition name, and no notification — by design.

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How to read it honestly

• It is a picture, not a verdict. It cannot tell you why a rhythm looked irregular, and an "irregular" read is not evidence that anything is wrong — just as a "steady" read is not reassurance that your heart is healthy.
• Beat-to-beat timing looks "irregular" for lots of harmless reasons: normal variation, the occasional extra or skipped beat that most healthy people have, breathing, movement, or simply an imperfect optical reading. It's structurally prone to false positives, which is exactly why it stays descriptive.
• It is not a substitute for a professional. If you ever feel faint, have chest pain, shortness of breath, palpitations that worry you, or any symptom that concerns you — contact a qualified professional or your local emergency service straight away. Do not rely on NOOP.

Privacy

All processing happens on your own device. No heartbeat data is ever sent anywhere. The feature stores nothing until you've opted in, and you can turn it off at any time.