The single most critical variable in true Heart Rate Variability analysis is the uncorrupted calculation of individual R-R intervals (the exact time in milliseconds between successive heartbeats).
If the underlying hardware misses a millisecond, the mathematical reality of your autonomic state is corrupted. Because we do not smooth, dampen, or approximate your data, Hrv.live enforces strict hardware standards.
Polar H10 Chest Strap
The Polar H10 is universally recognized in clinical and sports science research as the gold standard for portable electrocardiogram (ECG) data transmission. It captures raw electrical signals directly from the heart muscle, delivering true millisecond accuracy. We confidently rely on the metrics generated by this sensor. The Mayo Clinic, FDNY, and individual NFL and MLB teams do as well.
Garmin / Wahoo ECG Chest Straps
While these secondary chest monitors utilize identical electrical tracking principles to measure R-R intervals and may interface with our Web Bluetooth API, variations in manufacturer firmware mean we cannot explicitly guarantee uncompromised data fidelity over long testing blocks.
Apple Watch, Whoop, Oura, Fitbit
These devices will not work with our live engine. Consumer wristbands and smart rings do not measure the electrical activity of the heart. Instead, they use optical sensors (Photoplethysmography, or PPG) to guess heart activity based on blood volume changes under the skin.
While optical tracking is fine for estimating historical averages while you sleep, it is fundamentally incapable of capturing the immediate, raw millisecond fluctuations required for live, time-domain biofeedback.
Disclaimer
hrv.live, rmssd.com, and Time Domain Labs tools are for informational and educational purposes only. Not a medical device. Not FDA cleared or approved. No medical advice is provided.
We do not diagnose, treat, cure, or prevent any disease or medical condition. RMSSD, pNN50, and RR interval data are measures of autonomic activity, not a medical diagnosis.
Do not use this information to make medical decisions. Always consult a qualified healthcare professional for medical concerns. If you have a medical emergency, call 911.
You assume full responsibility for use of this site and its data.