Topic Guide
Heart Rate Variability — Complete Guide
HRV is the most useful number on your wearable. It reflects how your autonomic nervous system balances rest and stress, and it responds within hours to sleep, training, alcohol, and illness. This page collects everything we have written about HRV — start with the foundational article, then drill into the specifics that matter to you.
Start here — foundational reading
Article · 5 min
What Is HRV and Why It Matters
The big picture — what HRV measures, why higher is generally better, and how it powers 6 health indices.
Article · 7 min
HRV Accuracy: Garmin vs Polar vs Fitbit vs Withings
Which wearable measures HRV most accurately? Independent research compared against ECG ground truth.
Article · 4 min
How Stress Affects Your HRV
Acute vs chronic stress signatures in your HRV trend, and what to do about each.
Core concepts
Glossary
Heart Rate Variability (HRV)
Plain-language definition with examples and reference ranges by age.
Glossary
RMSSD
The actual HRV metric your wearable reports — what it stands for and how to read it.
Glossary
Autonomic Nervous System
The system HRV actually reflects — sympathetic vs parasympathetic balance.
Glossary
Stress Score
How wearables turn HRV into the daily stress number you see in your app.
Calculators & tools
Device-specific guides
Comparison
Polar vs Garmin
Two heavyweight HRV tracking ecosystems compared — algorithm, accuracy, ergonomics.
Comparison
Polar vs Fitbit
Athlete tools vs everyday health — two very different HRV philosophies.
Comparison
Fitbit vs Garmin
Smoothed wellness vs detailed sport metrics — pick the right HRV view for your goals.
Devices
All Supported Wearables
Polar, Fitbit, Withings, Strava, Garmin — what each provides for HRV tracking.
MyBodyAI normalizes HRV from any wearable against age- and sex-matched references — switch devices freely and keep one continuous trend.
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