Training Readiness
Readiness is a weighted average of the recovery signals you actually have. Anything your setup cannot measure is left out, not filled in.
- It reads sleep, heart rate variability and resting heart rate from Health Connect or Apple Health, plus how you say you feel.
- With a watch or ring it is a full score. With a phone alone it leans on any sleep your phone records and on how you say you feel.
- Heart rate variability carries the most weight once you have a personal baseline. Before that, sleep counts for more.
- Yesterday's fuelling and your cycle phase are shown beside the score as context. A normal cycle never lowers it.
A weighted average
Readiness is a weighted average of whatever recovery signals are actually available for you, not a fixed number with bonuses and penalties bolted on.
Watch, ring or phone
Kriterion reads its signals from Health Connect on Android or Apple Health on iPhone. Connect a watch or ring and readiness reads your heart rate variability and resting heart rate every morning, alongside last night's sleep. With a phone alone there is no overnight heart data to read, so the score leans on any sleep your phone records into Health Connect or Apple Health, and on how you say you feel. A night you type in by hand feeds your sleep card but not readiness, because a remembered number of hours is not a measurement.
What counts most
Heart rate variability carries the most weight once there is a personal baseline to compare it with, because it is the most direct read on whether your nervous system has recovered, and population ranges for it are wide enough that one person's normal is another's warning. Until that baseline exists it counts for less than sleep. Sleep is scaled by how much of it your device actually measured: a reading of duration alone is real evidence, just less of it than a full staged night. A heart reading more than a day old is left out.
Supporting signals and context
Resting heart rate and how you say you feel count too, with less weight. Reviews of athlete monitoring have found simple self-reported measures track training stress at least as well as many objective ones, which is why one tap on how you feel is worth asking for. If you track a regular cycle, the usual shift in your vitals after ovulation is allowed for, so it is not mistaken for poor recovery. Your cycle phase is shown beside the score as context and never moves it. Yesterday's fuelling is shown beside the score as context rather than counted in it: it tells you something real, but it is not equivalent to an autonomic measurement.
When something is missing
Anything your setup can't measure is dropped and the remaining weights rebalance, so a score built without a wearable is honestly a score about sleep and how you feel rather than one padded out with neutral filler. With too little measured, the score is pulled towards neutral rather than allowed to swing on one signal.
- Your heart pounds, flutters or races at rest, and it keeps coming back or lasts more than a few minutes
- You get palpitations and have a heart condition, or a family history of heart problems
Readiness is free in Kriterion. Connect a watch or ring and it reads your HRV and resting heart rate every morning; with a phone alone it is honestly a score about your sleep and how you feel, never padded out with guesses.
References
- Plews DJ, Laursen PB, Stanley J, Kilding AE, Buchheit M. Training adaptation and heart rate variability in elite endurance athletes: opening the door to effective monitoring. Sports Medicine, 2013;43(9):773-781.
- Buchheit M. Monitoring training status with HR measures: do all roads lead to Rome? Frontiers in Physiology, 2014;5:73.
- Bellenger CR, Fuller JT, Thomson RL, Davison K, Robertson EY, Buckley JD. Monitoring athletic training status through autonomic heart rate regulation: a systematic review and meta-analysis. Sports Medicine, 2016;46(10):1461-1486.
- Saw AE, Main LC, Gastin PB. Monitoring the athlete training response: subjective self-reported measures trump commonly used objective measures: a systematic review. British Journal of Sports Medicine, 2016;50(5):281-291.
Last reviewed 28 Sep 2026 · Next review due Sep 2029
Kriterion is the app this reasoning is built into
It measures your maintenance calories from what you actually ate against what the scale actually did, tells you how firmly the number is pinned down, and checks its own past predictions against your results. Free logging, UK food data, and no ads.
Join the list and you get the founding offer: the launch price, held for as long as you stay subscribed. It is capped at the first 1,000 subscribers or 90 days from launch, whichever comes first, and it will not be extended. One confirmation now, one email on launch day. Not a newsletter.