Pulse, Morphology &
Optical HRV

Mean heart rate over the recording, from detected pulse-peak intervals. On long recordings the displayed value is the median of per-epoch HR.

Share of the recording that survived both the per-pulse quality gate and the motion gate — the best at-a-glance trust indicator.

Mean per-pulse quality, combining template correlation, amplitude and the local motion index. A separate axis from event confidence.

Share of detected pulses passing the SQI threshold — the quality side of the analyzability budget, before the motion gate.

Fraction of raw pulse intervals replaced during cleaning, gated against a robust running median of accepted intervals.

The average foot-to-foot interval (ms) — the optical analogue of the mean NN interval; the reciprocal of mean HR.

Ratio of pulsatile (AC) to steady (DC) optical signal — how strong the pulse is at the sensor. Low PI flags weak contact or vasoconstriction and predicts noisier HRV.

Share of pulses occurring during high-motion spans (motion index > 0.5) and down-weighted. The inertial gate is what separates true pulse variability from movement artifact.

Average of the 0–1 motion index across the recording — an overall restlessness summary.

Effective accelerometer sample rate recovered from the inertial stream — surfaced for provenance and diagnosing thin motion data.

Effective gyroscope sample rate. Gyro-only sessions still drive the motion gate but cannot resolve posture.

The primary parasympathetic (vagal) marker — valid even on short windows. Tracks ECG rMSSD at rest but runs slightly higher under motion.

Overall HRV — total autonomic variability. Withheld on ultra-short windows where it is not interpretable.

rMSSD on a log scale — the right-skew correction that makes day-to-day readiness changes roughly linear.

Percentage of successive interval pairs differing by more than 50 ms — a vagally-mediated measure.

Dispersion perpendicular to the line of identity — instantaneous beat-to-beat variability, tied to rMSSD.

Dispersion along the line of identity — longer-term variability, related to SDNN.

Balance of short- to long-term variability.

Area of the fitted Poincaré ellipse — a single geometric summary of overall dispersion.

Ratio of low- (0.04–0.15 Hz) to high-frequency (0.15–0.40 Hz) power. Historically read as sympatho-vagal balance, contested — treat as directional.

Absolute power in the very-low, low and high bands plus normalised units (LFnu, HFnu). HF aligns with respiratory sinus arrhythmia; VLF needs an overnight-length record.

Short-term fractal scaling of the interval series (4–16 beats). α1 ≈ 1 marks healthy correlated dynamics. Sensitive to record length and editing.

Regularity of the interval series — lower means more repetitive dynamics. A node-computed complexity descriptor on optical PPI.

Time from pulse foot to systolic peak (crest time) — a direct timing fiducial that lengthens with vascular stiffening.

Full width of the pulse at 50% of its systolic amplitude — a direct timing measure related to vascular resistance.

Timing of the dicrotic notch relative to the foot — marks the systolic–diastolic transition. Emitted only when a notch is detected.

Whether a dicrotic notch and following diastolic peak are resolvable on the downslope — gates the reflection indices below.

Relative height of the reflected (diastolic) wave vs the systolic peak — an arterial-reflection / stiffness proxy. Typically negative in young arteries.

Reflected (diastolic) peak as a fraction of the systolic peak — rises with arterial stiffening.

Ratio of the early-systolic b wave to the a wave of the acceleration-PPG — the most age/stiffness-correlated SDPPG index; strongly negative in young compliant arteries, rising toward 0 with stiffening.

Composite of the five SDPPG waves (a–e), a published vascular-aging proxy that rises with arterial age. Emitted only when all five fiducials resolve.

Rate of cyclic bradycardia–tachycardia oscillations per hour — the autonomic fingerprint of repetitive apnea/arousal, from pulse intervals alone. A screen, not a diagnosis; corroborated against oximetry in the Integrator.

A 0–100 readiness headline blending vagal HRV against your recent baseline. An internal composite, not externally validated.

A resting HR-ratio fitness estimate — a population proxy, not a cardiopulmonary exercise test.

Body/limb position class from the gravity vector, with left/right lateral split by magnetometer heading when available. Off-data windows resolve to unknown, never fabricated.

Relative magnetic heading of the limb (deg), gravity-component removed. Uncalibrated for true north — used only to separate left- from right-side lateral posture.

A calibration-free quality flag: set when the field magnitude wobbles in a still window or sits >25% off baseline. Informational only — it does not alter beat SQI here.

Mean agreement between PpgDex’s pulse intervals and the device’s — high agreement confirms the optical detector tracks the same beats as Polar’s firmware.

Average absolute difference (ms) between self- and device-derived mean pulse intervals — the agreement metric in raw milliseconds.

A flagged interval where the motion index stayed above 0.5 across consecutive beats. Emitted as a low-prior quality event so consumers can exclude the span.

Spans with collapsed perfusion or no resolvable pulse are excluded from HRV rather than filled. Unparseable timestamps surface as null (Clock Contract), never “now.”