Readiness score

The recovery-score convergence: nearly every wearable vendor now compresses activity, training load, vitals, sleep, and HRV into a single daily "how hard should you go" number — Oura and Whoop pioneered it, Garmin has Body Battery/training readiness, and with Series 12 / Ultra 4 Apple joins in (apple-watch): a 0-10 score mapped to four recommendations (Recover / Pace yourself / Ready / Go for it). Apple's differentiator is intraday updates — the score responds to a hard workout or shifted daytime vitals instead of freezing at the morning calculation. rob-ter-horst's open question: are these scores stable and meaningful, or noisy derivatives? Enabled by raised sampling rates (HR every 5 s, HRV every 5 min) — the score is only as good as the measurement stream feeding it.

First real-world data (dc-rainmaker's Ultra 4 review, a week of wear): the intraday dynamics work — 7 "Ready" on waking → 5 after a mountain ride → 3 "Pace yourself" after a hard track session, "relatively in the ballpark of how I felt." Category bands: 0-1 Recover, 2-4 Pace Yourself, 5-7 Ready, 8-10 Go For It; requires 7 nights × 4+ hours before any score; baseline runs to 49 days. Two caveats: super buggy at launch (scores absent for minutes-to-hours; Ultra 4 and Series 12 updating out of sync on identical sensors), and the baseline-divergence problem — on ~5 hours of sleep Garmin scored him 1/100 while Apple said 2, because Apple's week-old baseline had already normalized his bad sleep. Same-inputs scores are only as comparable as their baselines.

Sources: Quantified Scientist analysis, DC Rainmaker Ultra 4 review