heala
Recovery & sleep · 4 min read
HRV only means something as YOUR trend
Two people wake up to the same HRV: 55 ms. For one it is a red flag, for the other a personal high. HRV carries almost no meaning as a raw number — only as a deviation from your own baseline.
Two people, one number
Person A's overnight HRV has averaged 72 ms for the past month. This morning it reads 55 — a 24% drop, the kind that follows a hard training week, a late night of drinking, or the first day of a cold. Person B has averaged 44 ms since they started measuring. This morning theirs also reads 55 — the highest number they have ever logged. Same reading, same units, same morning. Opposite meanings.
There is no lookup table that resolves 55 ms into good or bad. The number only becomes information next to the owner's history. For A it is a flag worth respecting. For B it is a sign that whatever they have been doing lately is working. Any app, article, or friend that grades your HRV without knowing your baseline is guessing.
Why raw numbers don't transfer
Resting HRV across healthy adults spans roughly 20 to over 100 ms. Age moves it: HRV declines through adulthood. Genetics move it more — two healthy, equally fit 30-year-olds can sit a factor of three apart and both be fine. Fitness nudges it, but nowhere near enough to overcome the genetic spread. A high baseline is not a trophy and a low one is not a diagnosis.
Devices widen the gap further. One wearable reports a full-night average of rMSSD; another takes a spot reading during deep sleep; a chest strap measures a five-minute morning window. These are different rulers. Comparing your 48 to a friend's 80 across two brands compares nothing at all. The trend within one device, on one body, is the part that travels.
What HRV cannot tell you
HRV cannot rank you against anyone else, and it cannot diagnose anything — though it can dip a day or two before a cold announces itself. It cannot tell you why it dropped: a hard session, three drinks, late caffeine, a warm bedroom and an oncoming illness can all produce the same morning number. It also moves with the menstrual cycle, typically running lower in the luteal phase, so a monthly dip can be hormones rather than overtraining.
And a single low reading cannot tell you anything on its own: night-to-night wobble of 10–20% is normal. One reading is weather; the rolling line is climate. Treat any one morning as a question, not a verdict — and if the line stays low for weeks while you feel genuinely unwell, that is a conversation for a doctor, not a wearable.
Reading your own trend
The fix is mechanical. Take seven days of consistent readings and average them — that is your baseline. Keep the average rolling, and read each morning as a deviation from it, not as a level. Research on elite athletes points the same way: weekly-averaged HRV tracks training adaptation better than any single day's value. A morning 15–25% below your own rolling line, for two or three mornings running, is worth acting on. The same absolute number on someone else's line means nothing.
This is how Heala's morning recovery score reads HRV: as a deviation from your own rolling baseline, weighed alongside sleep, resting heart rate and yesterday's strain — never as a raw number graded against a population. It works without a watch, using whatever signals you have. The score's job is to hold the conversation with your baseline so you don't have to do the arithmetic before coffee.
Make your number mean something
Overnight or same time each morning, same device. Consistency beats precision — you are building a ruler, not taking an exam.
Ignore the first week. A 7-day rolling average needs seven days. Judge nothing until the line settles.
A reading 15–25% below your own baseline for 2–3 days is a signal. A low absolute number is not.
Alcohol, illness, a hard session, poor sleep, stress, late caffeine, cycle phase. The drop is the alert; your log is the explanation.
Quick answers
What is a good HRV score?
There isn't one. Healthy adults span roughly 20 to over 100 ms, driven mostly by age, genetics and the device's measurement method. 55 ms is a strong reading for one person and a warning sign for another. The only benchmark that means anything is your own rolling baseline; good is at or above it.
Why is my HRV so much lower than my friend's?
Most likely genetics and age; possibly the hardware. Different devices measure different windows — a full-night average, a deep-sleep spot reading, a five-minute morning test — and the numbers are not on the same ruler. A lower baseline does not mean worse fitness. The comparable part is direction: how each of you trends against your own line.
How long until my HRV baseline is useful?
About a week of consistent readings gives a first baseline; two to three weeks show your normal day-to-day wobble, which you need before deviations mean anything. Measure the same way at the same time each day. Studies of athletes consistently find weekly-averaged HRV more informative than single-day readings, which is why a rolling average is the default.
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