A step is a specific movement of a wrist and a specific pattern of acceleration, which is why a watch can tell walking from waving. Mine records walking, with a cadence, between two and four in the morning, while the sleep tracking says I am not moving.
I wear the watch to bed because it tracks sleep, which I started doing after a bad year when I was not getting any.
What it does with your arm at night is the part nobody thinks about. It is still recording. The accelerometer runs all night and the sleep staging is worked out from how still you are and from your heart rate.
So there are two records for every night. The sleep record, which says what stage I was in minute by minute. And the activity record, which says what my arm was doing.
They agree, every night, for years, in the way you would expect: I am asleep, my arm is still, no steps.
Except in this house.
I moved in in 2021.
Since then, roughly two nights a week, the activity record has between three thousand six hundred and four thousand four hundred steps, between about two and four in the morning.
Four thousand steps is a little under two miles.
The sleep record for exactly those minutes says deep sleep, with a heart rate in the low fifties, which is what mine does when I am properly under.
The cadence is the thing that has stopped me writing it off.
The activity data is not a lump. It is minute by minute, and you can pull it out of the app as a table, which I did, and each minute has a step count in it.
Those minutes are between ninety eight and one hundred and six steps.
That is a walking cadence. A brisk one, but a completely ordinary human walking cadence, held steady for forty minutes at a time.
A watch that is being jolted, or that is on a wrist being flung around by a dream, does not produce a hundred steps a minute for forty minutes. It produces bursts and then nothing. I know what that looks like because I have made it look like that on purpose, sitting up in bed shaking my arm, and the pattern is unmistakable and it is not this.
Things I have done, over four years, in the order I did them.
Changed the watch. Twice, and the second time to a different brand entirely with a different app and a different way of counting.
Same nights, same cadence, same numbers within a couple of hundred.
Taken it off at night and left it on the bedside table. This is the one everybody suggests and it is a good idea.
On the table it records nothing. Flat, all night, every night, for the six weeks I tried it.
That proves less than it looks like it proves. It does not show the watch on my wrist doing the walking. It proves that whatever the watch is measuring, it measures it when it is on me and not when it is on a table two feet away.
Slept somewhere else. My mother's for a week at Christmas, twice. A hotel for work, eleven nights across three years. My sister's spare room.
Nothing. Not one step, anywhere else, in four years.
The house.
It is a 1950s semi and I am the fourth owner. I have the deeds and there is nothing in them, and the neighbours have been here since the eighties and are lovely and say nothing about it has ever been strange.
The thing I looked for, obviously, is whether I am walking. I am fifty and I have never sleepwalked in my life and my ex would have mentioned it.
So I put a camera in the bedroom. My own, a little one, pointed at the bed, for a month, which is a thing I did entirely for myself and which nobody else has ever seen.
I caught seven of them.
I am in the bed. All seven, the whole time. You can see the duvet move when I turn over twice and otherwise nothing happens for four hours.
And the app for those nights says three thousand nine hundred, four thousand one hundred, four thousand, and so on.
The distance.
I have gone furthest with this and I am aware of how it sounds.
Four thousand steps is about two and a half miles at my stride, which I have measured.
The upstairs landing of this house, corner to corner, end to end, is eleven metres if you walk the whole of it including into both bedrooms and back.
Two and a half miles is about three hundred and sixty five laps of that.
At a hundred steps a minute, forty minutes, that is roughly nine laps a minute, which is not possible for anybody in a house this size, and I did the arithmetic on that at three in the morning with a calculator and a piece of paper on my knee, which tells you what four years of this does.
So whatever the watch is measuring is not walking round my house.
What I have settled into.
I still wear it. That is the sentence I keep coming back to as evidence about myself rather than about the house.
I wear it because the sleep data is genuinely useful and because I sleep badly and because a person who has been sleeping badly for six years will keep anything that helps.
I have muted the weekly summary, which used to arrive on a Monday and tell me I had smashed my step goal.
And I have stopped looking at the minute by minute table, because in the March I noticed something in it that I have not been able to unnotice, which is that the cadence is not perfectly steady after all.
It slows, very slightly, for about ninety seconds in the middle of every one of them. From a hundred and two down to about eighty and then back up.
It is the same in all of them, at roughly the same point, about eighteen minutes in.
Which is what walking looks like when somebody stops for a moment on the way somewhere, and then carries on.