Why your heart never beats the same way twice

If your heart beats sixty times a minute, it is easy to picture exactly one second between each beat. That is wrong, and fortunately so. The real gap varies from beat to beat: nine hundred and forty milliseconds, then a thousand and ten, then nine hundred and eighty. Those gaps are not noise. They are the essential part.

Two pedals, always

Heart rhythm is governed by two opposing branches of the autonomic nervous system, the one that runs without your attention. One speeds it up, the other slows it down, and they never both stop at once.

What you observe at any instant is therefore the result of an arbitration, not an instruction. The heart is not told to beat at sixty: it continuously receives two contrary influences whose balance keeps shifting. That moving balance is what produces the irregularity.

Breathing shows up in the heartbeat

There is one variation anyone can observe on themselves. Heart rhythm speeds up slightly on the in-breath and slows down on the out-breath. The phenomenon has a name, respiratory sinus arrhythmia, and it is more pronounced the slower and deeper the breathing.

This is why a heartbeat recording already contains, with nothing added, the trace of a person’s breathing. A calm conversation and a heated one are not breathed the same way, and that reads in the gaps between beats before it reads in their count.

Everything moves it

Variability is not a personal constant. It changes with almost everything that crosses a day.

• Body position: lying down, sitting, standing, the values are not comparable.
• Time of day: it follows a cycle over twenty-four hours, with a trough and a peak.
• Last night’s sleep, yesterday’s exercise, a meal, alcohol.
• Age, which lowers it slowly and steadily in everyone.

This is why comparing your value to someone else’s makes little sense, and why a capture is mostly compared to itself: what matters is what moves within the half hour, not the level it sits at.

What half an hour contains

The arithmetic is simple, and it explains why the duration of a capture matters so much. At seventy beats a minute, half an hour produces a little over two thousand of them. Each is separated from the next by a gap, so a thirty-minute capture contains roughly two thousand gaps, all different.

That is a great deal for an artwork, and very little for a statistic. Two thousand intervals are plenty to draw a dense shape and to bring out the moments where the rhythm shifts; they would not be enough to conclude anything about a person, and that is not what they are asked to do.

Ten minutes remains the protocol minimum for that reason: below it, there are enough beats to make a graph, not enough to make a composition that holds together.

What it does not say

A variation indicates that something happened in the body. It says neither what nor why. An acceleration can come from a feeling, a memory, a sip of coffee, a change of posture, or a sentence you are about to say.

A heartbeat says something happened. It never says what.

No method allows you to work back from a heart rhythm to a thought. That is a physical limit, not a technological gap, and it is what makes the medium bearable: what gets said during a capture stays between the two people present.

What an artwork makes of it

An Arsentis composition does not represent an average value. It represents movement: the moments where the rhythm climbs, those where it settles, and the steady ground between them, which stays black and holds the drawing together.

It is also what makes two artworks impossible to confuse. Two people never produce the same sequence of gaps, and one person does not reproduce it twice. It is a consequence of how a heart is governed.