Why Does Your Body Shake When You're Nervous?

I've always found this kinda stupid.

You have an interview.

You're about to speak in front of people.

You're asking someone out.

Or you're waiting for something important.

There's literally no physical danger.

Nobody is chasing you.

You're just sitting there.

And suddenly your body is like:

WE ARE GOING TO DIE.

Heart going crazy.

Hands cold.

Stomach feels weird.

You start sweating.

And sometimes your hands or even your entire body starts shaking.

Like bro relax 😭

So why does this actually happen?

Turns out your body isn't being completely stupid.

It's running a survival system that's WAY older than interviews, presentations and awkward conversations.

Your body basically has an emergency mode

Your nervous system has something called the autonomic nervous system.

It's responsible for a bunch of things you don't consciously control.

Heart rate.

Blood pressure.

Digestion.

Sweating.

Pupil size.

Stuff like that.

And one part of it is the sympathetic nervous system.

Think of this as:

oh shit mode.

When your brain thinks something threatening is happening, this system starts preparing your body to deal with it.

Historically, that threat might actually have been dangerous.

Predator.

Enemy.

Fight.

Something trying to kill you.

The problem is that your nervous system doesn't only react to lions.

It can react to:

"Tell us about yourself."

😭

Your brain doesn't really care that the threat isn't physical

This is the interesting part.

You KNOW the interviewer isn't going to murder you.

But your brain can still interpret the situation as threatening.

Why?

Because humans care enormously about social outcomes.

Rejection.

Embarrassment.

Failure.

Being judged.

Losing status.

Uncertainty.

Your brain isn't sitting there logically calculating:

Threat classification: Software engineering interview. Physical mortality probability: 0.0001%. Remain calm.

It detects:

IMPORTANT + UNCERTAIN + POSSIBLE BAD OUTCOME

and starts preparing you.

That's why you can have a full physical stress response while sitting perfectly safely in a chair.

Then adrenaline enters the chat

Once the stress response kicks in, your body releases stress hormones, including adrenaline (epinephrine).

And adrenaline is basically your body's:

WE NEED PERFORMANCE RIGHT NOW

chemical.

Your heart starts beating faster.

Your airways open more.

Blood flow gets redirected.

Energy becomes rapidly available.

Your pupils can dilate.

You become more alert.

Your muscles become ready for action.

This is extremely useful if you need to run away from something.

Slightly less useful when you need to calmly explain the difference between optimistic and pessimistic locking.

Okay, but why the shaking?

This was the part I actually wanted to understand.

Your muscles aren't just pieces of meat that switch between:

ON

and

OFF.

They're controlled by motor neurons.

A motor neuron controls a group of muscle fibers, forming something called a motor unit.

Your nervous system can recruit different numbers of motor units and change how frequently they're activated depending on how much force you need.

When you're stressed, your whole motor system becomes more activated.

You're essentially primed for movement.

Your muscles become more tense.

Your nervous system is sending stronger signals.

Adrenaline is circulating.

And tiny muscle contractions that normally aren't very noticeable can become much more obvious.

The result?

Shake.

Shake.

Shake.

Your body has prepared for physical action...

while you're trying to stand still.

It's basically acceleration while holding the brake

This is how I like thinking about it.

Imagine sitting in a car.

Your foot is pressing the accelerator.

But you're also holding the brake.

The engine wants to GO.

The car is being held still.

That's roughly what's happening when you're extremely nervous but physically stationary.

Your sympathetic nervous system is going:

MOVE. DO SOMETHING. WE NEED ACTION.

Meanwhile you're sitting there going:

🙂 yes, I have approximately three years of experience with React.

That mismatch contributes to the trembling feeling.

This is also why your muscles get tense

Ever noticed your shoulders when you're stressed?

Sometimes they're practically touching your ears.

You might clench your jaw.

Tighten your hands.

Tense your legs.

You often don't even realize you're doing it.

Your nervous system is preparing muscles for movement.

Again, useful if you're about to fight something.

Not particularly useful while reading an email.

Why do your hands shake so much?

Hands make trembling really obvious because they're used for extremely precise movements.

Tiny fluctuations in muscle activity that you'd barely notice somewhere else become visible when you're holding your hand out.

It's also why trying to do something precise while extremely nervous can become difficult.

Signing something.

Holding a glass.

Typing.

Using tools.

Suddenly you're consciously thinking:

WHY IS MY HAND DOING THAT

Which, naturally, makes you even more nervous.

Excellent system.

And then there's the feedback loop

This is probably the most annoying part.

You get nervous.

↓

Your hands shake.

↓

You notice your hands shaking.

↓

OH FUCK THEY CAN SEE I'M NERVOUS.

↓

You become more nervous.

↓

More adrenaline.

↓

More shaking.

↓

"STOP SHAKING."

↓

Even more shaking.

😭

Your brain has basically created a self-sustaining nervousness machine.

Why can't you just tell yourself to stop?

Because most of this isn't under direct conscious control.

You can't simply command:

adrenaline = 0

in the same way you can decide to move your arm.

The autonomic nervous system is, well...

autonomic.

That's useful.

Imagine having to consciously remember:

"Okay heart, beat."

"Alright lungs, breathe."

"Digest lunch now."

You'd die the first time you got distracted.

But the downside is that when your automatic systems decide something is dangerous, your conscious brain doesn't have an instant OFF button.

This explains why saying "don't be nervous" is useless

Has anyone in human history stopped being nervous because someone said:

"Bro just don't be nervous."

Oh wow.

Why didn't I think of that?

Thanks.

The reaction isn't purely intellectual.

It's physiological.

You can logically know you're safe while your body is still behaving like something horrible is about to happen.

That's why anxiety can feel so physical.

Because it literally is.

Why does breathing slowly actually help?

This is where things get cool.

Your autonomic nervous system has another major branch:

The parasympathetic nervous system.

If sympathetic activity is roughly:

GO GO GO

parasympathetic activity is closer to:

we're safe, calm down.

Slow breathing, especially with longer controlled exhales, can influence autonomic activity and help reduce physiological arousal.

Your heart rate can come down.

Your body starts relaxing.

And your brain gets another piece of information:

Maybe we're actually okay.

This isn't magic.

You're basically manipulating part of the physical stress response from the other direction.

Instead of:

calm brain → calm body

you're partly doing:

calm body → calmer brain

Which I find really interesting.

Exercise can help too

This also makes intuitive sense once you understand the system.

Your body prepared for movement.

So...

move.

Walking.

Running.

Gym.

Even just moving around before something stressful can sometimes make you feel better.

You're giving all that physiological activation somewhere to go.

This is also why pacing around while nervous feels surprisingly natural.

Your body is basically saying:

THANK YOU. FINALLY WE'RE DOING SOMETHING.

Why does this get better with experience?

This is probably the most useful part.

Remember your first few interviews?

Terrifying.

Then after you've done twenty?

Still stressful.

But usually not the same.

Same with public speaking.

Dating.

Driving.

Gym.

Basically anything initially unfamiliar.

Your brain learns.

You've experienced the situation.

Nothing catastrophic happened.

Then you did it again.

Still alive.

Again.

Still alive.

Eventually your nervous system starts updating its prediction.

Apparently this isn't actually a tiger.

That's why exposure works so well for many fears.

You're not just intellectually convincing yourself.

You're giving your nervous system evidence.

This is also why confidence comes AFTER doing things

I used to think:

First you become confident.

Then you do the scary thing.

I'm increasingly convinced it's usually backwards.

You do the scary thing while nervous.

Your body freaks out.

You survive.

You do it again.

You survive again.

Eventually your brain stops treating it like an emergency.

Then people call you confident.

Confidence is often just your nervous system having enough historical data to say:

yeah we've done this before.

Your body isn't trying to sabotage you

This is probably the funniest realization.

When you're shaking before something important, your body isn't malfunctioning.

It's actually trying to help.

Your brain detected something important.

So it increased alertness.

Raised your heart rate.

Mobilized energy.

Prepared your muscles.

Made you hyper-aware of your environment.

It's basically saying:

Don't worry bro, I've prepared us for combat.

And you're like:

I'M ASKING HR ABOUT SALARY.

😭

The system works.

The context changed.

We're running ancient hardware in a very weird modern world

That's basically what I take away from this.

Our nervous system evolved in an environment completely different from the one we live in today.

The threats changed.

The machinery didn't.

A predator can trigger your stress response.

But so can:

An interview.

A first date.

A presentation.

An exam.

A difficult phone call.

Waiting for someone to reply.

Walking into a room full of strangers.

Your body doesn't always distinguish between physical danger and psychological threat as cleanly as you'd like.

So next time your hands start shaking before something important, instead of thinking:

what the fuck is wrong with me?

remember what's actually happening.

Your sympathetic nervous system has activated.

Adrenaline is circulating.

Your muscles are primed.

Your brain has decided something important is happening.

Your body isn't weak.

It's preparing you for a fight.

It's just approximately 100,000 years late in figuring out what we're fighting.