ECG vs PPG for HRV biofeedback comes down to one practical question: how much do you trust the timing?

Why this comparison matters

A lot of breathwork products talk about calm, vagal tone, or HRV without saying much about sensor quality. But if the promise involves beat-to-beat feedback, the sensor path matters. ECG and PPG are not interchangeable when you start caring about timing fidelity and repeatable HRV comparisons.

Where ECG usually has the advantage

Chest-strap ECG gives you a stronger foundation for HRV biofeedback because it is closer to the heart signal itself. That makes it a safer default for guided resonance sessions, especially when the app is comparing breathing rates or trying to identify a better personal target instead of simply animating a pacer.

• ✓Better timing fidelity for beat-to-beat workflows
• ✓More appropriate for users who want stronger measurement confidence
• ✓A better match for guided resonance sweeps and follow-up sessions

Where PPG can still be useful

Optical sensors are more convenient and more common. That matters. For broad wellness use or simpler pacing workflows, PPG may be good enough. The tradeoff is that when you want tighter HRV comparisons, optical timing can be less dependable than chest-strap ECG.

What this means for RHz

RHz is intentionally positioned around external monitor quality rather than treating every heart rate source as equivalent. That is why Polar H10 is the recommended setup, why the app is framed as local-first and measurement-aware, and why the landing page leans toward users who want more than a generic calm timer.

This page is also a useful SEO wedge for users comparing device classes before they commit to any one product ecosystem.