The Weight of a Heartbeat

Today I made an interesting observation. I wanted to weigh the model that I had created, so I stepped onto the scale to weigh myself first and then pick up the model and calculate the difference.

As a child I always only used a digital scale. One that lets you stand for a while and then presents you with a number.

But this one here was a purely mechanical one, with an indicator and a scale. And of course it is always moving a bit when you're standing on it. But I wanted to get a measurement as precise as possible.

So I watched the indicator very closely and tried to stand very still to figure out where exactly between 81 and 82 kg it was standing. It looked like the exact middle, but it kept swinging.

I wondered if my feet were doing some micro-movements, so I tried to stand as still as possible, and tried to do everything to stop the indicator from moving.

Sometimes, while breathing very slowly, almost holding my breath, the movement got very subtle and almost stopped, but then it continued, in a surprising regular way. It almost looked like a heartbeat. But I was the only one here with a heart.

So I touched my wrist to feel my heartbeat, and indeed, what I was seeing on the scale was synchronous with what I was feeling.

And of course when I was breathing out slowly, my heartbeat would slow down as well as the movement of the indicator. When I was breathing in, my heartbeat would accelerate, and the movement of the indicator would become more excessive.

I was wondering how it was possible that my heartbeat created a force on the scale, even though I could not feel anything in my feet. The movement of the indicator ranged around 0.5 – 1.5 kg, nothing much, maybe not enough to feel it in my feet, but still considerable.

Was it maybe the fact that my heart was not a continuous but a pulsating pump and that maybe it was moving more blood downwards than upwards?

What would explain why the indicator moved towards less weight at the beginning of its oscillation. The blood accelerating downwards creates a tiny amount of thrust while the blood from the capillaries is moving rather continuously back to the heart.

I gotta ask Per if he thinks that is possible.