HRV and Recovery Explained: Why Your Own Baseline Matters

What HRV measures

Your heart does not beat like a metronome. The small variations between beats change with rest, effort, sleep and stress. RMSSD is a standard short-term measure of that variation; lnRMSSD is its natural logarithm, which makes day-to-day changes easier to compare.

Why nightly, not spot readings

Daytime spot readings change with posture, movement, breathing and caffeine. Measured during sleep, conditions are steadier, so nightly HRV is more comparable from one day to the next. ATS-1 uses nightly lnRMSSD and keeps daytime spot HRV out of its indices.

Why your own baseline

HRV differs a lot between people and between devices, so a single "good" number is not meaningful for an individual. ATS-1 compares each person with their own 28-day rolling baseline, using robust statistics. See the State Index.

From HRV to recovery speed

Recovery is how quickly a dip returns toward the person's usual level. ATS-1 estimates it from natural day-to-day changes in nightly HRV as a recovery rate and a half-life. See Resilience.

Device differences

Devices compute HRV with different algorithms, which is why ATS-1 requires the device model, firmware and algorithm version on every record, and flags sleep stages as low-confidence.

A wellness measure

ATS-1 is for research and general wellness only. It does not diagnose, treat, prevent or predict any disease, including any mental health condition. For questions about your own health, speak to a healthcare professional.

Questions

What is a good HRV?

For one person, the useful comparison is with their own baseline rather than a population number, because HRV varies widely between people and devices.

Keep reading

Resilience (recovery half-life)How ATS-1 measures resilience as recovery speed: an AR(1) model of nightly HRV gives a recovery rate λ = −ln φ and a half-life t½ = ln 2 / λ over 60 days.State IndexThe ATS-1 State Index: robust z-scores of HRV, sleep and affect against a 28-day personal baseline, using the median and MAD.Plane methodsHow ATS-1 collects each plane: nightly lnRMSSD, sleep timing, provenance, IEEE 1752.1 mapping, WHO-5 every 14 days and sampling rules.Early-warning signals explainedWhat early-warning signals are, why recovery slows near a shift, what group studies found, and why one person's signals are uncertain.

Take the next step.

What heart-rate variability is, why nightly lnRMSSD against your own 28-day baseline beats daytime spot readings, and how recovery speed is measured.

Resilience index Get the textbook

HRV and recovery, explained