Do wearable readiness scores have evidence behind them?
Wearable readiness score validation: a 2025 review of 14 composite scores from 10 makers found little to no peer-reviewed validation. What has been tested.
A 2025 review of 14 composite health scores from 10 wearable manufacturers concluded that the composite indices themselves have undergone little to no validation in the peer-reviewed literature. None of the manufacturers disclosed the exact formulas or the weighting of each input. The signals that feed the scores are a separate question from the scores themselves.
What goes into a readiness or recovery score?
Doherty et al., Translational Exercise Biomedicine 2025 identified the scores from a previously published umbrella review and from the ten manufacturers with the largest market share. They include WHOOP Recovery, Oura Readiness, Garmin Body Battery and Training Readiness, Fitbit Daily Readiness, Polar Nightly Recharge and Samsung Energy Score.
Across the 14 scores, heart rate variability (HRV) was an input in 86%, resting heart rate in 79%, and physical activity and sleep duration in 71% each. Design choices differed: Fitbit’s score uses a 7-day baseline and Polar’s a 28-day baseline. The HRV input has its own evidence base, covered in our post on HRV trends.
Disclosure: the paper states no conflict of interest, but co-author Marco Altini lists himself on his own website as a data science advisor at Oura, whose Readiness score is among those reviewed.
Has anyone tested whether the scores track anything?
Rarely, and mostly in small samples. Lundstrom et al., 2024 studied 23 NCAA swimmers (10 male, 13 female) during heavy training. Swimmers whose metabolism was suppressed, measured by resting metabolic rate in the laboratory, had lower WHOOP-derived HRV (81 versus 110 ms, p = 0.04), and HRV correlated with resting metabolic rate (r = 0.45, p = 0.03).
Results for the composite metrics were less clear. In males, strain correlated with the recovery-stress balance on the stress questionnaire (r = 0.69). In females, none of HRV, resting heart rate, strain or recovery correlated with the stress variables. This was a cross-sectional study of one device, and it tested associations with laboratory and questionnaire measures, not whether a score predicts performance or illness.
The gap is one of evidence, not a finding that the scores are wrong. Untested and inaccurate are different claims.
The bottom line
- A 2025 review of 14 composite scores from 10 manufacturers found little to no peer-reviewed validation, and no disclosed formulas.
- HRV (86%), resting heart rate (79%), activity (71%) and sleep duration (71%) are the most common inputs, and each is a measurable signal.
- In one small study of 23 swimmers, wearable HRV tracked laboratory metabolism (r = 0.45), while results for strain and recovery differed by sex.
Frequently asked questions
- Are WHOOP recovery and Oura readiness scores accurate?
- The 2025 review found that composite scores have had little to no peer-reviewed validation, and companies do not disclose the formulas. Their accuracy is therefore largely untested rather than shown to be poor. Individual signals such as heart rate and HRV are a separate question, with their own studies.
- What data goes into a readiness score?
- In a review of 14 scores, 86% used HRV, 79% resting heart rate, 71% physical activity and 71% sleep duration. Baselines vary: Fitbit uses 7 days and Polar 28 days. The weighting of each input is not published by any of the manufacturers reviewed.
Sources
- Doherty C, Baldwin M, Lambe R, Burke D, Altini M, 2025. Readiness, recovery, and strain: an evaluation of composite health scores in consumer wearables. Translational Exercise Biomedicine, volume 2, issue 2, pages 128 to 144.
- Lundstrom EA, De Souza MJ, Koltun KJ, Strock NCA, Canil HN, Williams NI, 2024. Wearable technology metrics are associated with energy deficiency and psychological stress in elite swimmers. International Journal of Sports Science & Coaching, volume 19, issue 4, pages 1578 to 1587.