Signals watched
5
Resting heart rate, wrist temperature, HRV, respiratory rate, blood oxygen.
Feature
Early Warning
The signals that shift before you feel anything are already on your wrist. The hard part is telling a real pattern from a warm bedroom, and not crying wolf.
Early Warning compares five overnight vitals, resting heart rate, sleeping wrist temperature, HRV, respiratory rate and blood oxygen, against a median baseline built from your own recent history, excluding the last two days so an episode in progress cannot raise the bar it is measured against. It raises a level only when several signals move together, or one stays off for two days running. It is a training decision aid, not a diagnosis, and Apex Health: Recovery Coach is not a medical device.
Baseline
Median, gap-adjusted
Excludes the most recent two days, so an ongoing episode does not move its own goalposts.
Alerts
At most once a day
And silent while clear. An all-clear notification every morning is noise.
Why several signals, and not one
Any single vital moves for boring reasons. A warm bedroom raises wrist temperature. A late glass of wine raises resting heart rate and flattens HRV. A cold room, a heavy meal, a stressful day, or simply a poorly-seated watch will all nudge one number.
Acting on a single reading produces constant false alarms, and an alerting system people stop believing is worse than none. What is genuinely informative is co-movement: several independent signals drifting the same way at the same time, or one signal staying off for several consecutive days.
So the level only rises when at least two vitals are outside their normal range together, or one has been outside for two days running. Three or more together escalates further.
The baseline excludes the present
A subtle but important design detail. If you build a baseline from the last twenty-one days including today, then an episode that has been building for three days is partly baked into the reference it is being compared against. The longer something goes on, the more normal it looks.
Early Warning therefore builds its median from your history excluding the most recent two days. Today is judged against your normal from before the episode began.
The same logic applies to the multi-day streak: each day in the streak is scored against a baseline built only from the days before it, so a slow seasonal drift, a bedroom that has been getting warmer all month, does not read as a ten-day illness.
It adjusts for the menstrual cycle
Wrist temperature and resting heart rate both rise measurably through the luteal phase. That is normal physiology, not an immune response, and an alerting system that does not know the difference will flag half of every cycle.
When cycle data is available in Apple Health, Early Warning widens its tolerance on exactly those two signals for the phase, and says so on screen. The other three signals are unaffected. See how cycle phase feeds the rest of the app.
What it is not
It cannot detect illness, and it does not claim to. It has no diagnostic capability, it is not a regulated medical device, and a clear reading is not evidence that you are well.
What it does is narrower and genuinely useful: it tells you when your own physiology has moved away from your own normal, so you can make a better decision about whether today is a day to train hard. If something stays off for several days, or you feel unwell, that is a conversation for a doctor, not an app.
Common questions
Can Apex Health: Recovery Coach tell me I am getting sick?
No. Early Warning compares five vitals against your own recent baseline and reports when several have moved together, a pattern that often precedes feeling unwell, a rough reaction to alcohol, or genuine overreaching. It cannot diagnose anything, it is not a medical device, and a clear result does not mean you are healthy. If something stays off for several days or you feel unwell, speak to a doctor.
How long before it works?
It needs at least seven days of vitals before it will make any judgement, and it improves with more. Until then it says plainly that it is still building your baseline rather than guessing. It also requires reasonably recent data: if your most recent tracked day is more than a day old, it reports the gap instead of judging week-old readings as though they were this morning's.
Will it wake me up with alerts?
No. It delivers at most one alert per day, only when the level is raised, and only from background health updates rather than while you are using the app. When everything is within range it stays silent.
Wake up to a verdict, not a spreadsheet.
Apex Health: Recovery Coach turns the Apple Health data you already generate into one clear decision each morning. Free, private, and entirely on your device.
Apex Health: Recovery Coach provides general wellness and fitness information computed from your own data. It is not a medical device and does not diagnose, treat, or prevent any condition. Always consult a qualified professional for medical concerns.