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Learn · Signal quality

ECG and PPG can both measure pulse timing. They do it differently.

For resonance-breathing biofeedback, the useful question is whether a device provides dependable beat-to-beat timing throughout a quiet guided session.

Chest-strap ECG

Chest straps detect the heart's electrical activity close to the source and can provide individual beat timing with less smoothing. RHz recommends Polar H10 and similar ECG straps for the strongest timing quality.

Optical PPG

PPG devices detect pulses optically. Their fit, motion sensitivity, processing, and broadcast behavior can affect the data available to RHz. WHOOP 5.0 has been tested for use with RHz, but connection alone does not guarantee actual beat-to-beat intervals. When a device sends only heart rate, RHz estimates intervals instead; this is not equivalent to measured HRV.

Choose for the workflow you want

If you already own a monitor, check that it broadcasts actual beat-to-beat intervals. For RHz, Polar H10 is the recommended option. Whatever compatible sensor you use, follow its fitting instructions and keep sessions still and consistent.

Continue learning

Review the setup guide, compare ECG and PPG sensors, or return to the RHz overview.

Ready to begin?

Install RHz on Android, connect a compatible monitor, and start with a guided breathing session.