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  "path": "/index.php?topic=298353.msg740985#msg740985",
  "publishedAt": "2026-02-20T23:10:35.000Z",
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  "textContent": "Important distinction: wrist-based HRV relies on photoplethysmography (PPG), which estimates inter-beat intervals from blood flow rather than directly measuring cardiac electrical activity like ECG. That inevitably introduces more noise and wider margi...",
  "title": "Re: Study: Garmin smartwatch measures certain health metric with large margins of error"
}