Recovery and the nervous system
A readiness score is a product opinion, not a measurement
Two devices reading the same body produce different scores because they weight inputs differently. Neither weighting has been validated against outcomes.
Every recovery platform reduces a night of physiology to one number between zero and a hundred. That compression is a design decision, and different companies make it differently.
The short version
- Readiness scores combine HRV, resting heart rate, sleep metrics, and sometimes temperature through proprietary weightings.
- Those weightings are not published and have generally not been validated against performance or health outcomes.
- Two devices worn simultaneously routinely disagree, sometimes substantially.
- The underlying inputs are more informative than the composite that hides them.
What goes into a score
Typically: overnight heart rate variability, resting heart rate, sleep duration and estimated stages, recent training load, and sometimes skin temperature deviation. Each input is measured or inferred with its own error, then combined through a weighting the manufacturer chose.
This is where the intellectual property sits, which is why the weightings are not disclosed. It is also why the number cannot be independently evaluated.
Why two devices disagree
If one platform weights HRV heavily and another weights sleep duration heavily, a night of short but restful sleep produces very different scores. Neither is wrong. They are answering slightly different questions and presenting both answers with the same confident single number.
Anyone who has worn two devices simultaneously has seen this. It is the clearest available demonstration that the score is a model output rather than a measurement.
Using the inputs instead
Most platforms let you see the components. Look at those. Resting heart rate trending up across several days alongside HRV trending down is a coherent signal that means something. A score of 62 does not tell you which of those is happening.
Then apply the oldest available instrument: does the session feel harder than it should? Subjective effort remains a well-validated measure and it is free.
Common questions
Should I skip training on a low score?
Not automatically. Use it as one input alongside how you feel, how the warm-up goes, and what the session demands.
Are any of these scores validated?
Published independent validation against meaningful outcomes is scarce across the category. Treat the number as a heuristic.
Sources
- AI health wearables in 2026 — https://www.aimagicx.com/blog/ai-health-wearables-smart-rings-monitors-guide-2026
- Wearable tech and biometric guide — https://ethicalbiohacking.com/wearables