The signals
- Heart rate variability (HRV): the small changes in time between heartbeats. Higher than your usual generally means your nervous system has recovered; well below it often follows hard training, poor sleep, alcohol or illness.
- Resting heart rate: a few beats above your own normal overnight is one of the clearest signs something is taxing you.
- Sleep: how long you slept against what you need, and how steady your timing is.
- Some devices also use breathing rate and skin temperature, which tend to rise early when you are getting ill.
Why your own normal is the point
HRV varies enormously between healthy people, so an HRV of 40 ms is neither good nor bad on its own. What carries information is the change from your own baseline over the last few weeks. A good score means today looks like a good day for you, not for an average person.
That also means a score needs a couple of weeks of data before it is meaningful, and a single night is noise. Trends matter more than one morning.
How to use it
Treat a low score as a reason to look at what changed (a late meal, alcohol, a hard session, a short night, something coming on) rather than as a verdict. Train hard on high days, keep it easy on low ones, and do not chase the number from one day to the next.
How Life OS scores it
Life OS reads HRV, resting heart rate, sleep and recent strain from Apple Health and scores each against your own normal, so a typical day for you lands around 75, not 52. It shows what moved the score and keeps the overnight heart rate curve under it, so you can see the night the number came from.
Questions people ask
What is a readiness score based on?
Mostly heart rate variability, resting heart rate and sleep, each compared with your own recent baseline. Some devices add breathing rate and skin temperature.
Is a higher HRV always better?
Not across people: healthy people differ widely. Within one person, HRV above their own usual generally means good recovery, and well below it suggests strain, poor sleep, alcohol or illness.
Why is my readiness low when I feel fine?
Often one input is off (a late meal, alcohol, a short night) or the score is comparing you with too short a history. A score built against your own normal over a few weeks is more trustworthy than one night or a population average.