Notes · 03
Fire your readiness score.
A product feature — not a clinical biomarker.
Wearable grade
“82”
Opaque mix of noisy signals
Honest build
Baselines
Raw RMSSD + RHR · your range
We will not claim
biological age
diagnosis
longevity score
autonomic balance
low HRV = low electrolytes
HRV / PRV can be a corroborating tracer of stress (heat, hard sessions, under-replaced fluid) — never a deficiency diagnosis by itself.
What the evidence actually says
0
mortality link · genetically-predicted low HRV · UK Biobank MR (n=412,891)
>2×
RMSSD spread · healthy same-age adults · 8M devices
14 / 10
readiness scores / brands · none prospectively validated
Four things the literature is clear on:
- What it measures isn’t HRV. Optical wrist and ring sensors read pulse-rate variability — a vascular signal offset from the heartbeat by pulse-transit-time — not ECG HRV. Close at rest; it decouples with motion, heat, and in chronic illness, stiffer older arteries, and darker skin.
- More HRV doesn’t buy years. Low measured HRV tracks worse outcomes, but that’s a mirror, not a lever: in UK Biobank, genetically-predicted low HRV showed no link to mortality. HRV reflects your systemic state; it doesn’t set it.
- The grade is a sealed box. Readiness / recovery scores run on undisclosed weightings a firmware update can change overnight, and they sample HRV during wearable sleep stages that don’t match a sleep lab — noisy input before the math even starts.
- There is no “normal” to grade you against. Across 8 million devices, healthy 30-year-olds of the same sex differ in RMSSD by more than 2×. The only honest reference is your own multi-week baseline — the exact thing a proprietary grade hides.
A readiness score is a product feature in a lab coat. Watch your own raw baseline; ignore the grade.
Sources: Topol, The Big Holes in Wearable HRV & Readiness · UK Biobank HRV Mendelian randomization (PMC10558565) · HRV in 8 million wearables · 14 readiness scores, 10 brands, none published