Recovery
Three people wearing three devices through the same night will wake up to three different numbers. All three are calculated correctly. Understanding why they disagree is most of what you need to use any of them well.
A recovery score — also sold as readiness, Body Battery or training readiness — is a single number estimating how prepared your body is today, built almost entirely from three overnight measurements: heart rate variability, resting heart rate and sleep. Brands weight those three differently and compare them to different baselines, which is why they disagree. None of them can see what you ate.
It is a summary, not a measurement. Overnight your device records a handful of physiological signals, compares each one to what is normal for you, weights them, and collapses the result into one number between 0 and 100 — or a percentage, or a color, or a battery icon.
The value of that is real: it saves you interpreting four trends before breakfast. The cost is that a single number hides which input moved and by how much, and every brand hides it differently.
Despite very different marketing, the major devices measure substantially the same things:
| Device | Called | Main inputs |
|---|---|---|
| WHOOP | Recovery (1–100%) | HRV from the last slow-wave sleep cycle, resting heart rate, respiratory rate, sleep performance, blood oxygen and skin temperature |
| Oura | Readiness (0–100) | HRV, resting heart rate, body temperature, previous night’s sleep, sleep balance over several days and recent activity balance |
| Garmin | Training Readiness / Body Battery (0–100) | HRV status over 7 days, sleep, recovery time, acute training load, stress history |
| Apple Watch | Vitals / Training Load | Overnight HRV, resting heart rate, respiratory rate, wrist temperature, sleep duration |
Strip the branding and it is the same three pillars everywhere: HRV, resting heart rate and sleep, with temperature and respiratory rate as supporting evidence.
Four reasons, and none of them is a bug:
The consequence is simple: a recovery score is only comparable to itself. Comparing your 62 to a friend’s 88 on a different brand is meaningless, and so is comparing this week’s numbers to a device you wore last year.
This is the limitation nobody selling a device leads with. A recovery score is built entirely from what a sensor can detect at your skin. Three of the most powerful influences on how recovered you actually are never reach it:
NutriMacro calculates a recovery score from the HRV, resting heart rate and sleep your watch already records — and then shows it next to the sessions you logged and the food you ate, which is the half no recovery wearable can see. A red week stops being a mystery when the calorie deficit that caused it is on the same screen. It reads from Apple Health, Google Fit, Health Connect and Samsung Health, so you keep the watch you have.
Most brands treat roughly 67 percent and above as green, 34 to 66 as amber and below 34 as red, but the bands are arbitrary and brand-specific. What matters is your own range. If you typically sit in the 60s, a 60 is a normal day rather than a warning, and a sustained run in the 40s means more than any single number.
Because they measure different windows, compare to different baselines and weight the inputs differently. WHOOP takes HRV from your last slow-wave sleep cycle while others average the night; Oura weights sleep balance heavily; Garmin folds in acute training load. The underlying physiology is the same, the arithmetic is not. Scores are only comparable to themselves.
Usually not on the strength of one low score. Open the inputs first. If HRV is down but resting heart rate and sleep are normal, it is most likely noise and you should train as planned. If HRV is down, resting heart rate is up and you slept badly, take the easy day. Several consecutive low days is a much stronger signal than any single morning.
Each overnight input is compared to your personal baseline, converted into a deviation, weighted and combined into one number. The three that do most of the work everywhere are heart rate variability, resting heart rate and sleep, with respiratory rate, blood oxygen and skin temperature acting as supporting evidence.
Three common reasons. Your device may not have learned your baseline yet, which takes about two weeks. You may be measuring in a way that systematically reads low, such as a loose strap. Or something genuine and invisible to the sensor is going on, most often a sustained calorie deficit or heavy resistance training that the device under-counts as load.
Not by itself. It can show you a sustained depression in HRV and a rising resting heart rate, which is part of the picture, but genuine overreaching also involves stalled performance, poor sleep, low motivation and often under-eating. Those need a training log and a food log, which no wearable score includes.
A recovery score is only as good as what it can see, and none of them can see your food. NutriMacro builds one from the HRV, resting heart rate and sleep your watch already records, then shows it beside the training and the calories that actually moved it.
NutriMacro is a nutrition and training tracker for iPhone and Android. It logs food by barcode, photo or search, counts food in slices and units rather than grams, and keeps strength training, GPS activities, sleep and recovery in the same daily view. It runs in the language of your phone across 108 countries.
Read next: What is a good HRV? HRV vs resting heart rate What is a good sleep score?
