Your normal is yours.

Ask what a good resting heart rate is and you will get one answer for everyone, usually 60 to 100 beats a minute. Ask tens of thousands of people to measure their own and you will get a spread so wide that one answer for everyone stops meaning much. Mere is built on the second answer.

Averages describe crowds

In one large study, researchers analysed the daily resting heart rate of 92,457 adults in the US who wore a wearable tracker for a median of 320 days (Quer et al., 2020). The average was 65 beats per minute. Individual averages ran from 40 to 109, and the authors note that one person's normal can differ from another's by as much as 70 beats. Age, sex, body mass index and sleep duration, taken together, accounted for less than a tenth of the difference between people.

Picture two friends of the same age who run together. One wakes at 52 beats a minute, the other at 74. Both can be entirely ordinary. Set either against an average and you learn little about them. Set each against their own history and a change becomes easier to see.

Heart rate variability, the small shifts in timing from one beat to the next, tells the same story. HRV tends to fall with age, rise with aerobic fitness, and move with breathing, posture and the time of day (Shaffer and Ginsberg, 2017). As they put it, "a healthy heart is not a metronome." A review of 44 studies covering 21,438 healthy adults found large differences between individuals, and values that also depended on how they were measured (Nunan et al., 2010). A reading that is ordinary for one healthy person can be unusual for another.

You are steadier than the crowd

Here is the useful part. In the same resting heart rate study, each person was far more consistent over time than the population was (Quer et al., 2020). For most people it moved by only about 3 beats within a typical week, though one in five had at least one week when it swung by 10 beats or more. Across the year, the group average drifted by about 2 beats, peaking in early January and easing to its low by late July.

That steadiness is what makes a personal baseline worth having. Your normal is a narrow band; the crowd's is a wide one. A shift of ten beats would disappear inside a population chart. Against your own normal, it can stand out, especially when it lasts.

Why Mere spends 14 nights learning you

So Mere starts with you. For the first 14 nights, the ring reads your heart rate, HRV and blood oxygen while you sleep, along with the shape of your pulse: its rise, peak, notch and echo. For those two weeks, the point is not to compare you with anyone. It is to learn what normal looks like for your body.

Why two weeks? One night is a snapshot, and any single week can be unusual. Fourteen nights take in each day of the week twice, along with the things that fill them: a hard workout, a late dinner, a short night. A normal is more useful once it has seen a little of ordinary life.

What a change from your normal can mean

Many changes have everyday explanations. Recent exercise, breathing and posture all move HRV (Shaffer and Ginsberg, 2017). In a study of 4,098 working adults in Finland, drinking alcohol on a given day was linked to a higher heart rate and lower HRV in the first hours of sleep that night, and more drinks to bigger changes (Pietilä et al., 2018). Resting heart rate even shifts a little with the time of year (Quer et al., 2020).

So a change is a question, not a verdict. Mere puts it in plain English, as a pattern such as Steady, Wired or Drained, so you can decide what to do with it: an earlier night, an easier run, a quieter evening.

If something stays away from your normal for a while and you cannot explain it, a conversation with your doctor may be helpful. The ring notices. Your doctor decides.

Everybody is different. Your normal is yours, and it is the one worth knowing. Join the founding list to hear when Mere opens.