Apple Watch uses photoplethysmography (PPG) to measure heart rate intervals, which correlates strongly with gold-standard ECG measurements for HRV analysis. While not medical-grade, it's sufficiently accurate for detecting meaningful changes in autonomic nervous system function during daily life.

We primarily use RMSSD (Root Mean Square of Successive Differences) as it's most sensitive to parasympathetic nervous system activity and can be calculated reliably from short measurement windows. We also track SDNN and other time-domain metrics for comprehensive assessment.

Research shows that controlled breathing can influence HRV within 30-60 seconds. Our real-time monitoring typically shows measurable changes within the first minute of guided breathwork, with more significant improvements over 3-5 minute sessions.

HRV biofeedback has extensive clinical validation for stress reduction, anxiety management, and performance enhancement. While Wellobit itself is a consumer wellness app, our approach is built on the same scientific principles used in clinical HRV biofeedback devices.