Can You Trust Your Oura or Whoop Readiness Score?

Strip a readiness score down to its inputs and the picture inverts. When researchers put five popular wearables on 13 adults for 536 nights and checked them against a clinical ECG, the raw nocturnal signals held up cleanly: the Oura Gen 4 tracked resting heart rate to within about 2 percent of the ECG (CCC 0.98) and overnight HRV to within 6 percent (CCC 0.99). Oura led the field, WHOOP landed in the moderate range, and Polar was weaker, but the top devices measure these raw signals accurately enough to run a protocol on (see [1]). Those are the ingredients your ring is reading while you sleep.

The number stamped on top is a different object. A 2025 review catalogued 14 composite health scores across 10 manufacturers, including Oura Readiness, WHOOP Recovery, Garmin Body Battery, Fitbit Daily Readiness, and Samsung Energy Score, and found that no manufacturer disclosed how the inputs are weighted, and not one score had been validated against an actual outcome (see [2]). Two rings can read the same heart rate and HRV and hand you a 61 and an 84, because the weighting is proprietary and undisclosed. You are trusting a marketing index, not a measurement.

So separate the two layers. The measurement layer, resting heart rate and HRV trend, is real signal, and the way to use it is a personal baseline: your own 7 to 14 day rolling average, and a flag when today sits more than roughly one standard deviation outside it. That is a number you can act on, because it is your data against your own history, not a black box comparing you to a hidden population model. Read the composite score as a soft nudge, not an instruction. If it says recover and your HRV, sleep, and training load all agree, that is three signals, not one.

None of this makes the score useless. It makes it a headline, and a headline you cannot audit deserves less weight than the two validated numbers underneath it. Track resting heart rate and HRV directly, hold them against your own baseline, and let the readiness number be the last input you consult. In Wellness Project you can pull that raw HRV and resting heart rate onto the Recovery page from Apple Health, Oura, or Fitbit and watch the trend itself rather than the score built on it.