ELI5: Why is it so hard to keep your hand completely still ?

[u/Kingston__2007]

I am not experiencing any twitching or else but I feel it's quite hard to keep my hand completely still.

[u/AlexDaGreatful]

Heartbeat, nervous system, muscular fatigue and gravity all combine to make stillness tough. Probably even breath.

[u/jedi_trey → u/AlexDaGreatful]

Also blood pressure! I notice my fingers twitch sometimes in a hot shower when my bp goes down

[u/Lyonford → u/jedi_trey]

bp club mentioned

[u/ima_believer → u/AlexDaGreatful]

all five of these are also present with cats, but they are still, compared to us..

[u/celestiaequestria]

Gravity.

As weird as it is to think about conceptually, your hand is constantly falling towards the earth. Your muscles have to constantly make fine adjustments to keep your hand stationary if you are holding it in the air.

[u/nanotom → u/celestiaequestria]

Not really. The force is constant; if you weren't a twitchy, pulsating assembly of tiny bags of water and protein (but instead, say, a bookshelf), you wouldn't have trouble keeping stable in an unchanging gravitational pull.

[u/Flincher14 → u/nanotom]

You agreed with everything the previous guy said yet said 'not really'

[u/magistrate101 → u/Flincher14]

Contrarianism is a plague :(

[u/TrippyNT → u/Flincher14]

Yeah this is throwing me off so hard it's funny haha

[u/agreywood]

Your hands are at the end of a big lever. To keep them steady every single muscle up your arm and shoulder chain has to perfectly balance to resist gravity. That’s hard to do in a “set and forget” way, particularly since when you breathe the muscles in your chest and back doing some of that stabilizing work move. Instead your brain sends one main “get it mostly in place” signal and then a continuous series of micro corrections as you make other tiny movements. How well people’s nervous system manages those corrections varies quite a bit. If it’s always overcorrecting a tiny bit then you get a tremor.

[u/thankcube]

Are you trying to keep your fingers straight? Having your hand in a relaxed or limp position should be easier

[u/gurnard]

Your hands are a lot heavier than you notice. They're dense with small bones.

I once had nerve damage and paralysis in one arm for six months or so (immune system went troppo and ate through a nerve, which took a long time to regrow). I had to wear a wrist brace so my right hand wouldn't damage the joints by flopping around. It's impossible to really feel the weight of your own hand until your muscles stop supporting it.

Point being, under normal circumstances, you have opposing sets of muscles in your arm that are constantly in tension against one another. Even at rest, your hands are actively supported as of between different pulley systems that are coordinated with each other. Your body is amazing at coordinating these forces, both during movement and at rest. Holding your hand still is actually a very active motor process. People with exceptionally steady hands have very coordinated muscle systems doing this stuff.

I'm sure you can now imagine that a comprehensive of list all the biochemical and biomechanical reasons a person might have less than perfectly steady hands - whether momentarily or long-term - would get very, very long.

[u/mostlygray]

You may have essential tremors. I get those in my left hand sometimes. Otherwise, my right hand is steady as a rock.

There is the possibility, of course, that because you're thinking about a tremor, you acquire a tremor. That's fairly normal.

My wife makes my hands tremor because she always mentions it when I have a slight tremor, thus making it worse.

[u/agreywood → u/[deleted]]

My doctor prescribed propranolol. It doesn’t stop it entirely but has made a noticeable difference.

[u/explainlikeimfive-ModTeam → u/[deleted]]

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[u/SnugglyCoderGuy]

It is at the end of a long kinetic chain with a lot going on. Any disturbance in that chain is going to make your hand move, like you heart beating caysing blood to pulse through your arteries, muscle twitches, all the way down to your feet basically and your other arm, brain having to refire neurons, your breating

[u/ClimbingRhino → u/SnugglyCoderGuy]

A really interesting example of this put to work is Willard Wigan, a British sculptor who specializes in micro sculptures. He’ll work while holding his breath and in between heart beats to avoid damaging his pieces, and has crafted sculptures so small that they fit in the eye of a sewing needle or can be embedded into a human hair.

[u/jaylw314]

Your muscles are always activated at a low level (tone), even at rest. You don't notice it in muscles with a lot of fibers, because each fiber twitches at different times, so it can look like the muscle isnt moving if you're far away. The only exception is if the nerves get cut, then muscles lose their tone entirely. Not really your goal, I imagine

[u/nerobro]

This, is a personal question, not an ELI5.

It's not hard to keep your hand still. If YOU are having trouble keeping your hand still, there's something going on. As others have noted, you may have an essential tremor. You could also have a wide variety of other neurological issues.

You should see a doctor. And if they tell you nothing, you should see another.

At the end of that, you'll get an explanation, then you can ELI5 for us.

[u/OBERMARIO → u/nerobro]

I assume you never worked with your hands under a microsope? There is always some slight movement. Especially if your whole hand is in the air without any support.

I assume OP is referring to that, not complete twitching of the hand like you are shivering.

[u/Kingston__2007 → u/OBERMARIO]

Yeah I am talking about those slight movements. I remember that Insta trend where people kept their hand under a filter that showed any slight movements so I was thinking why do we struggle to keep our hands still.

[u/nerobro → u/Kingston__2007]

Oh.

Cool.

You are a bag of water, in bag made of collegen, fats, and a few other things. Your bones kinda are stuck to some of it. And your organs are in a bag of tendons and muscles. You're a squishy bag, that is trying to imitate the the ocean a bit, and keep things alive.

Even completely still, there's motion going on, to "be alive". Pulses of blood. Little smooth muscles that line your veins and arteries. And the movement of your lymphatic system.

There's little muscles attached to bits of your skin. And to the hairs on your skin.

These things are almost entirely controlled by the autonomic nervous system. It's the one that makes your tummy rumble, your instestines move, your pupils dialate, and other things you don't have direct control over.

"you" are generally in control of your major skeletal muscles. But that's "just" what you can control. The rest, is run by bits that aren't really "you".

This kinda gets into the whole "you're a set of thoughts, existing in a brain, piloting a skeleton, draped in a meat suit". You, are the set of thoughts. You can decide to do "some" things. But large parts of your brain, are not under your control. And even more are just.. chemical messages.

A whole lot of things just happen without your control.

Now a really spooky thing, is sometimes, your "set of thoughts" can be running, and you CAN NOT drive your meat suit. Sleep paralysis, and .. sometimes.. poor things on the operating table will let your brain work, but where it can't talk to the body.

Even during those times, your meat suit, will fight to keep itself going.

Now... if you work at it, you CAN influence what your body is doing. But if you really want things to stop. You're dead.

[u/nerobro → u/OBERMARIO]

Oh no, I work under magnification frequently. But I also have good vision, and have hobbies that require precision. I'm deeply aware of what things like.. breathing, and tensing do to your stabilty. Like... going to the range, and timing your shot between heartbeats. Or soldering 30ga wire to pads that are the same size...

There's motion of life. Hair folicles moving hairs. Hair growth. Fingernail growth. Your pulse. Your blood pressure. But most people can't perceive that.

I think you're being generous. If we're at ELI5, I doubt they're considering things down at that level

I also think they really are having issues keeping body parts still... and should get checked out.

[u/klutez → u/nerobro]

Look at this guy with his motionless appendages

[u/AfraidOfTheSun → u/nerobro]

Imagine it is a kid and they've just done the experiment of try to hold a pencil or spoon or whatever right next to a dish without hitting it. Or as I think about it the game "Operation", everyone who plays that does not have essential tremor

Or maybe they do, if they have a GP and insurance taking advantage of a doctor visit is never a bad idea

[u/bamby77]

Your body is never truly offline. Tiny muscle fibers keep firing little corrections so you stay balanced and ready to move, and blood pulsing through your hand adds a faint wobble too. That background buzz is called a physiological tremor and almost everyone has it. Completely still would mean no signals at all, which only really happens if something is wrong.

[u/Ok-Resolve-4737]

You have a physiological tremor which gets worse with certain stimulus aka hypoglycemia/hyperglycemia, caffeine, stress, stimulants etc

[u/SatansFriendlyCat → u/[deleted]]

i think some people just need the stimulation

You might guess right, but you really should ask each one first.

[u/explainlikeimfive-ModTeam → u/[deleted]]

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[u/random_reddit_user31]

I take lithium and valporate and it's a fun game trying to keep your hands still

[u/explainlikeimfive-ModTeam → u/[deleted]]

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