The non-profit guide to HRV
Heart rate variability, measured and explained.
Lessons, answers and tools on the gaps between your heartbeats, each claim linked to its source, so you can read your own numbers and know what they say about your sleep, stress and recovery.
- lessons with quizzes
- 20
- questions answered
- 70
- terms explained
- 60
- studies and standards cited
- 325
Who this site is for
Everyone should be able to read their own HRV, simply to understand their body and health. People who look after others' health need it too.
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Everyone
Lessons and plain answers explain what moves your own HRV, from sleep and alcohol to training and a cold coming on, so you can read your body calmly instead of chasing a score.
Why everyone should understand their own HRV -
Doctors and health professionals
Sourced pages set consumer wearable HRV beside clinical Holter measures, so you can answer patients’ questions in a minute and point them to reading that keeps their expectations realistic.
HRV for doctors and health professionals: what your patients' wearables are telling them -
Health coaches
Baselines, 7-day averages and clear limits of scope give you a steady way to bring HRV into talks about stress, sleep and recovery, so clients stay curious rather than anxious.
HRV for health coaches: using it in conversations about stress, sleep and recovery -
Fitness instructors and trainers
Trial evidence on HRV-guided training and in-browser tools for raw RMSSD show what to track and what to ignore, so you can plan sessions on more than a readiness score.
HRV for fitness instructors and trainers: what to track and what to ignore
Find an answer
Ask any HRV question. Each answer starts with the short version and shows the studies behind it.
HRV in one picture
Two hearts at the same 60 beats a minute. One beats almost evenly; the other speeds up and slows down with each breath.
The gaps barely change.
The gaps rise and fall with each breath.
Understand it
Short lessons with quizzes that build step by step, from your first heartbeat to reading research, so you can judge your own data and the claims made about it.
- Level 1 Foundations Understand what HRV is and where it comes from.
- Level 2 Reading your numbers Read your own readings and trends with confidence.
- Level 3 Using HRV well Use HRV for training, stress and sleep, and spot misleading claims.
- Level 4 Analyst Follow a heartbeat from the sensor to every HRV number, and read a study or a device test with a critical eye.
Measure it
Tools that run in your browser. Nothing leaves your device unless you save it, so you can check a reading in private.
Reference guides
Long reads on the topics people ask about most, each with its sources.
From the blog
Longer pieces for the people who use HRV, from everyday readers to clinicians and coaches.
How we work
- Sourced. Every health statement links to its study or guideline.
- Private. Tool readings stay on your device.
- Non-profit. An educational project with nothing to sell. Why it exists