TL;DR
- The raw signals behind recovery scores — HRV and resting heart rate — are validated against ECG; the proprietary composite scores (WHOOP Recovery, Oura Readiness, Garmin Body Battery) are closed algorithms with little independent validation.[1]
- For HRV accuracy, rings lead: Oura Gen 4 reached a concordance correlation coefficient of 0.99 versus ECG, WHOOP 0.94, Garmin 0.87.[1]
- Use a recovery score as a personal trend line — the validation work that confirmed the HRV and RHR inputs explicitly put the devices' own recovery and readiness scores out of scope, and we are not aware of independent peer-reviewed validation of those composites.[1]
Recovery and readiness scores are the marquee AI-coaching feature of every modern wearable: a single 0–100 number that tells you whether to train hard or back off. This is a synthesis of the published evidence on how trustworthy those scores are — peer-reviewed validation studies and vendor documentation — not an in-house test. The evidence splits cleanly into two layers, and confusing them is the most common mistake users make.
The inputs are validated
Recovery scores are built mainly from nocturnal heart-rate variability (HRV) and resting heart rate, both measured at rest where motion artefact is minimal — and both validate well against ECG. Independent validation put Oura Gen 4 at a concordance correlation coefficient of 0.99 for HRV, Oura Gen 3 at 0.97, WHOOP at 0.94, and Garmin at 0.87, with rings also leading on resting heart rate.[1] So the data going into the score is real, and on a ring it is very good.
The composite score is a black box
What the vendor does with those inputs is the unvalidated part. WHOOP Recovery, Oura Readiness, and Garmin Body Battery are proprietary algorithms that blend HRV, resting heart rate, sleep, and other signals into one number using undisclosed weighting — and those composites have little independent peer-reviewed validation. The telling detail: the same ECG validation that confirmed the HRV and resting-heart-rate inputs explicitly placed the devices' own recovery and readiness scores out of scope, noting there is little transparency into what metrics feed each one — and we are not aware of independent peer-reviewed work that validates those composites against an outcome.[1] In other words, the ingredient is good but the recipe is unverified, so the final score can diverge from how recovered you actually are.
How the three big scores compare
| Score | Validated inputs | Composite validated? | Cost to access |
|---|---|---|---|
| WHOOP Recovery | HRV (CCC 0.94), RHR[1] | No independent peer-reviewed validation[1] | Membership from €199/yr[3] |
| Oura Readiness | HRV (CCC up to 0.99), RHR[1] | No independent peer-reviewed validation | $349 + $5.99/mo or $69.99/yr[4] |
| Garmin Body Battery | HRV (CCC 0.87), RHR, stress[1] | No independent peer-reviewed validation | Free on a compatible watch[5] |
What to act on
- Watch your own HRV and RHR trend: these are the validated parts, and direction over a week beats any single-day score.[1]
- Treat the recovery percentage as one input among several: cross-check it against perceived effort and training load, not as a verdict.[1]
- If accuracy of the raw signal matters most, a ring leads: Oura's HRV agreement with ECG is the strongest tested.[1]
Read your resting heart rate the validated way
Resting heart rate is the most trustworthy single signal feeding any recovery score, and it is most useful read against your age and sex. The Resting Heart Rate Calculator, for a 38-year-old male with a resting heart rate of 42 bpm, classifies it as Athlete and estimates a cardio age of 32 — these figures are computed live by the hub engine. This article is part of the 2026 Wearable & AI-Coaching Accuracy vs Value Index; for a device-versus-device recovery buying decision see WHOOP vs Garmin for recovery and the WHOOP 5 vs Oura Ring 4 vs Garmin three-way comparison.
Frequently asked questions
Are wearable recovery scores scientifically validated?
The inputs are; the scores mostly are not. The HRV and resting heart rate that feed WHOOP Recovery, Oura Readiness, and Garmin Body Battery are validated against ECG, but the proprietary composite scores that blend them are closed algorithms with little independent peer-reviewed validation.[1]
Which wearable measures HRV most accurately?
Rings lead. Independent validation against ECG put Oura Gen 4 at a concordance correlation coefficient of 0.99 for HRV, Oura Gen 3 at 0.97, WHOOP at 0.94, and Garmin at 0.87 — so the raw signal feeding the recovery score is most trustworthy on an Oura ring.[1]
Should I trust my WHOOP recovery or Oura readiness percentage?
Treat it as a directional trend, not a calibrated truth. The validation work that confirmed the HRV and resting-heart-rate inputs explicitly placed the devices' own recovery and readiness scores out of scope, noting there is little transparency into what feeds them, and we are not aware of independent peer-reviewed validation of those composites — so the score is best used as a personal pattern you correlate with how you feel.[1]
Is Garmin Body Battery the same kind of black box?
Yes, in validation terms. Body Battery is a proprietary composite like WHOOP Recovery and Oura Readiness; its inputs (HRV, RHR, stress) are validated but the blended score is not independently checked. The advantage is cost: Body Battery, HRV Status, and Training Readiness are free on a compatible Garmin watch.[5]
What recovery signal should I actually act on?
Your own nocturnal HRV and resting heart rate trend, which are the validated parts. Watch the direction over a week rather than reacting to a single recovery percentage, and pair it with how you feel and your training load.[1][2]
References
- 1 Validation of nocturnal resting heart rate and heart rate variability in consumer wearables (Oura, WHOOP, Garmin vs ECG) — Physiological Reports (Wiley) / PMC (2025)
- 2 Accuracy of Fitbit Charge 4, Garmin Vivosmart 4, and WHOOP versus polysomnography: systematic review — JMIR mHealth and uHealth (2024)
- 3 WHOOP membership options (One, Peak, Life tiers; device included with membership) — WHOOP (2026)
- 4 Oura Ring 4 product and pricing page ($349 start, $5.99/mo or $69.99/yr membership) — Oura (2026)
- 5 Garmin Connect+ premium app features (Body Battery, HRV Status, Training Readiness free; Connect+ optional) — Garmin (2026)