Most apps tell you to breathe at 6 breaths per minute.Your biology is unique.RHz uses high-fidelity HRV analysis to discover your personal Resonance Frequency—the exact Hz where your heart, lungs, and nervous system achieve maximum coherence.
Resonance · Readiness · Recovery · Resilience
External Heart Rate Monitor Required
Tested: Polar H10 (ECG) · Whoop 5.0 (PPG). Other devices may connect but results cannot be guaranteed—e.g., Garmin watches broadcasting HR may pair but produce unreliable HRV data.
iOS Version Coming Soon
Understanding Heart Rate Variability is the first step to optimizing it.
Your heart does not beat like a metronome. The time between each beat varies—sometimes by tens of milliseconds—and that variation is called Heart Rate Variability (HRV).
A higher HRV signals that your nervous system is flexible, responsive, and in a state of recovery. It is one of the most reliable indicators of cardiovascular fitness, stress resilience, and recovery capacity used by elite athletes and researchers worldwide.
A lower HRV indicates that your body is under load—whether from training, poor sleep, illness, or psychological stress. It means your sympathetic nervous system (the "fight-or-flight" response) is dominant, and your parasympathetic (rest-and-recover) branch is suppressed.
Rigid, equal intervals — metronome-like — sympathetic dominance
Natural variation in beat timing — parasympathetic tone — recovery mode
The gold-standard millisecond metric for short-term HRV. Reflects vagal tone and parasympathetic activity. Higher values generally indicate better recovery capacity.
Captures total variability across a full session. Reflects overall autonomic nervous system activity and is widely used for tracking training load and long-term adaptation.
The frequency-domain fingerprint of autonomic balance. RHz uses Astrophysics-Grade spectral analysis to map the precise power distribution across your HRV frequency bands.
Most breathing apps default to 6 breaths per minute—a population average. But research consistently shows that individual resonance frequencies span from approximately 4.5 to 7 BPM. Breathing at the wrong rate may feel calming, but it misses your biological peak.
Expansion
Protocol Status
Target Frequency
6.0 BPMGeneric App Default — One Size, Every User
Published biofeedback research shows the natural resonance range spans roughly 4.5 to 7 breaths per minute across individuals. The 6 BPM default is the statistical midpoint— not your personal optimum.
Your resonance frequency could sit anywhere in this range. RHz identifies yours to 0.1 BPM precision using the Lomb-Scargle spectral algorithm.
"Research consistently shows that individual resonance frequencies vary significantly. Training at a frequency even 0.2 BPM from your personal resonance produces a measurably weaker HRV response."
Based on resonance frequency biofeedback research — Lehrer & Gevirtz
Resonance breathing is not just slow breathing. It is a precise physiological feedback loop between your lungs, blood pressure, and heart.
Slow inhalation expands the chest and reduces intrathoracic pressure, directly modulating heart rate through mechanical coupling.
Blood pressure sensors (baroreceptors) in your aortic arch and carotid sinus detect the shift and relay signals to the brainstem via the vagus nerve.
At your specific resonance frequency, each breath maximally stimulates the vagus nerve—amplifying the HRV oscillation rather than simply calming it.
Heart rate, blood pressure oscillations, and respiration lock into a single coherent cycle—producing a peak HRV amplitude that is physiologically optimal.
The Key Insight
Breathing off-frequency produces a weak, incoherent HRV response.
At your exact resonance frequency, the same effort produces a surge—not a trickle.
A discrepancy of even 0.1 breaths per minute can be the difference between "relaxed" and "synchronized."
HRV is not just your heart rate—it is the space between beats, measured in milliseconds. A high RMSSD reflects strong vagal tone, robust recovery capacity, and a nervous system ready to adapt. RHz captures every interval.
When you breathe at your specific resonance frequency, you stimulate the vagus nerve with maximum efficiency—triggering a measurable surge in HRV amplitude that generic fixed-rate breathing apps fundamentally cannot achieve.
RHz uses the Lomb-Scargle Periodogram—the same algorithm astronomers use to detect periodic signals in stellar data—to map the precise power spectrum of your heart's response and identify your resonance peak.
✓ ECG Chest Strap — Best Accuracy
Tested: Polar H10
Directly measures the electrical depolarization of the heart's ventricles, pinpointing the exact millisecond of the R-wave. True beat-to-beat data with the timing precision required for accurate Lomb-Scargle spectral analysis.
⚠ PPG Optical Sensor — Reduced Accuracy
Tested: Whoop 5.0 · Others may connect but are unverified (e.g., Garmin watches)
Optical sensors estimate pulse via blood flow. During resonance breathing, large blood pressure swings introduce Pulse Arrival Time (PAT) jitter—a 2–3 beat propagation delay that can reduce spectral analysis precision. Results may vary.
Three steps from pairing to precision.
Connect a compatible Bluetooth heart rate monitor via BLE or ANT+. RHz displays live signal quality and raw beat-to-beat intervals before your first session begins.
A fully guided 20-minute session systematically tests your body across a range of breathing frequencies. The Astrophysics-Grade Lomb-Scargle algorithm maps your HRV power spectrum and identifies your resonance peak to 0.1 BPM.
Your personal frequency is locked in. Every future session paces you at your exact target. The Dynamic Resonance Engine monitors HRV in real time and adjusts pacing if your resonance drifts—keeping you optimized throughout.
A guided 20-minute "Sweep" stress-tests your body across different frequencies to find your mathematical resonance peak—not a generic starting point.
Continuously monitors your HRV in real-time. If resonance drops, it dynamically adjusts your pacing frequency to keep you optimized throughout the session.
Jump straight into an indefinite session. The app analyzes your historical data to start at your most effective frequency and auto-adjusts on the fly.
A biofeedback coach that filters out moment-to-moment noise and shows you exactly how well you are trending toward resonance—in real time.
You own your data. Export raw beat-to-beat RR intervals and calculated HRV metrics to CSV or JSON at any time for external analysis or research.
REAL-TIME SIGNAL ACQUISITION
Compatible with standard Bluetooth Heart Rate Monitors. Tested with the Polar H10 (ECG) and Whoop 5.0 (PPG). Other devices may connect but are unverified.
Your biometric data is among the most sensitive information that exists about you. RHz uses a hardened local persistence layer. Your physiological data is processed and stored entirely on-device and is never transmitted to any external server—ours or anyone else's.
Android Beta Coming Soon. Connect a compatible Bluetooth ECG heart rate monitor and complete your first Sweep in 20 minutes.
iOS Version Coming Soon
Hardware Required. An external Bluetooth Heart Rate Monitor is required. Tested devices: Polar H10 (ECG) and Whoop 5.0 (PPG). Other devices (e.g., Garmin watches broadcasting HR) may connect but HRV accuracy is not guaranteed.