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Basics

Start-here explainers, the core concepts and vocabulary behind reading your nervous system as a recovery instrument.

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Austin Spaeth July 9, 2026 Basics

Autonomic BP Indices: Kérdő, Robinson & Kvas

Four derived indices squeeze extra meaning from a simple blood-pressure-plus-pulse reading. The Kérdő vegetative index reads autonomic balance (near zero is balanced, positive leans sympathetic, negative leans parasympathetic). The Robinson index (rate-pressure product) estimates the heart's workload. The Kvas index and BCE both gauge circulatory efficiency, where lower is better. None of these are routine clinical tests (they are older physiology formulas), so their real value is watching your own trend, not one number.

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Alex Moliski / Unsplash Basics

Jul 9, 2026 · Austin Spaeth

Blood Pressure Basics: Systolic, Diastolic & Pulse

The three numbers on a blood-pressure reading each tell a different story: systolic is the peak as your heart contracts, diastolic is the resting pressure between beats, and pulse is how fast it all repeats. Here is what each one means and how a recovery-focused reading differs from the clinical chart.

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Mikhail Seleznev / Unsplash Basics

Jul 9, 2026 · Austin Spaeth

How to Measure HRV Accurately at Home

The secret to at-home HRV isn't an expensive device: it's consistency. Same time, same posture, same length, every day. Here's how to take readings you can actually trust, why the trend matters more than any single morning, and how to stop fooling yourself with noise.

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Zach Kessinger / Unsplash Basics

Jul 9, 2026 · Austin Spaeth

HRV Frequency Domain: VLF, LF, HF & Total Power Explained

Your heartbeat rhythm can be split into frequency bands, each reflecting a different piece of autonomic regulation. Here's what HF, LF, VLF and total power actually mean, why the mix matters more than the total, and how to read the LF/HF ratio without over-trusting it.

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Edwin Rodriguez / Unsplash Basics

Jul 9, 2026 · Austin Spaeth

HRV Histogram Metrics: Mode, AMo50, MxDMn and CV

Mode, AMo50, MxDMn and CV are the geometric HRV metrics: four different reads on the shape of your heartbeat-interval histogram. They're the raw ingredients behind the Baevsky stress index. Here's what each one describes and how to grade it.

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Priscilla Du Preez / Unsplash Basics

Jul 9, 2026 · Austin Spaeth

LF Peak, HF Peak, Coherence & Resonance Breathing

Frequency-domain HRV isn't only about how much power sits in each band: it's about where the power concentrates. Here's what the LF and HF peaks mean, why paced breathing pulls them into place, and how resonance-frequency breathing at about six breaths a minute maximizes your HRV.

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Rusty Watson / Unsplash Basics

Jul 9, 2026 · Austin Spaeth

Mean Arterial Pressure & Pulse Pressure, Explained

Systolic over diastolic is only the start. Two derived numbers, mean arterial pressure and pulse pressure, often say more about how well your circulation is actually perfusing your organs, and both are quietly informative in POTS and orthostatic intolerance.

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Max Nguyen / Unsplash Basics

Jul 9, 2026 · Austin Spaeth

PNS Index, SNS Index & Stress Index: The Balance Trio

Three numbers the app shows side by side to describe autonomic balance: the PNS index (your rest-and-recover side), the SNS index (your fight-or-flight side), and the Baevsky stress index. Here's what each one means and how they move together.

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Dan Burton / Unsplash Basics

Jul 9, 2026 · Austin Spaeth

Resting Heart Rate & Mean RR: Your Simplest Autonomic Signal

Resting heart rate is the plainest read on your autonomic load, and a creeping baseline is often the first sign of a bad stretch. Here's why position changes the number, how mean RR is the same information seen from beat-to-beat space, and how to read a rising resting HR in POTS recovery.

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Sarah Brown / Unsplash Basics

Jul 9, 2026 · Austin Spaeth

RMSSD and pNN50: Your Two Vagal-Tone Metrics, Explained

RMSSD and pNN50 are the two time-domain numbers that track vagal tone, the parasympathetic 'rest and digest' side of your nervous system. RMSSD is the cleanest day-to-day recovery signal you have. Here's what each one means and how to read them.

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Clay Banks / Unsplash Basics

Jul 9, 2026 · Austin Spaeth

RR Intervals & the Tachogram: The Raw Data Behind HRV

Every HRV number you'll ever see is built from one simple series: the time in milliseconds between your heartbeats. This is the plain-language explainer for RR intervals, the tachogram that plots them, and why a healthy trace looks like rolling waves rather than a flat line.

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Tom Nazaret / Unsplash Basics

Jul 9, 2026 · Austin Spaeth

The Autonomic Score & Grade Bands: One Number, Explained

Every colored tint in the app traces back to one system: a 0–100 readiness score and a ladder of grade bands from Excellent down to Crash, plus a violet Warning flag for readings that are suspiciously high. Here's how raw metrics become a single number, and how to read it without over-trusting it.

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Eneko Uruñuela / Unsplash Basics

Jul 9, 2026 · Austin Spaeth

What Is SDNN in HRV? Your Total Variability, Explained

SDNN is the broadest single HRV number: the standard deviation of the gaps between your heartbeats. Here's what it measures, why short readings run lower than the figures you see quoted, and how to read it as a recovery signal.

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The Autonomic Nervous System & Dysautonomia: A Complete Guide Basics

Jul 2, 2026 · Austin Spaeth

The Autonomic Nervous System & Dysautonomia: A Complete Guide

Your autonomic nervous system runs everything you never think about: heart rate, blood pressure, digestion, temperature. When it stops regulating properly, that's dysautonomia. Here is how it works, what goes wrong, and why it's measurable.

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What HRV Actually Is, And Why It Matters for POTS Recovery HRV

May 28, 2026 · Austin Spaeth

What HRV Actually Is, And Why It Matters for POTS Recovery

Heart rate variability is one of the clearest windows into your autonomic nervous system. Here is what it measures, why it drops in POTS and post-viral illness, and how to read it without obsessing.

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The Orthostatic Stand Test: How to Do It at Home (and What the Numbers Mean) POTS

May 21, 2026 · Austin Spaeth

The Orthostatic Stand Test: How to Do It at Home (and What the Numbers Mean)

The lying-to-standing heart rate test is the single most useful at-home measurement for POTS. Here is how to run it consistently and how to read the rise and recovery.

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Turn Months of Data Into a Five-Minute Doctor Conversation Recovery

May 14, 2026 · Austin Spaeth

Turn Months of Data Into a Five-Minute Doctor Conversation

Appointments are short and symptoms are hard to describe from memory. Here is how to use your own tracked data to walk in with a clear, specific summary your clinician can act on.

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Vitaly Gariev / Unsplash POTS

May 9, 2026 · Austin Spaeth

How POTS Is Diagnosed: The 30-BPM Rule, the Tilt Table & What to Expect

POTS is diagnosed by a sustained heart-rate rise on standing without a big blood-pressure drop, symptoms lasting months, and other causes ruled out. Here is what the criteria mean and what the tests feel like.

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