Jen Oliver: Welcome to the, so That's Why Podcast where we unpack the
science behind everyday questions.
I'm Jen.
Chris Smith: I'm Chris.
Matt Edmundson: And I'm Matt.
Jen Oliver: Okay, so today's question is something that every single person
listening will be able to relate to.
Why do we get pins and needles?
Matt Edmundson: Good question.
Uh, we all know that sensation, I dunno if you like me, where your
foot completely stops working.
And you're just sat there hoping no one gets to see you try and walk,
uh, in the next 30 seconds, right?
Chris Smith: And that, uh, foot won't work.
Situation is the perfect illustration because that distinctive buzz doesn't
happen when something goes wrong.
It's happening when things are actually being corrected,
Jen Oliver: Which goes against actually what we've all thought.
But by the end of this episode, you'll understand exactly what's happening at an
nerve level, why getting pins and needles feels the way it does, and crucially
why they are worth paying attention to rather than just shaking them off.
Matt Edmundson: Yeah, and also why your arm can go completely
dead from sleeping on it.
But then be entirely fine.
I dunno if you found this within just a few minutes, which always seems like
a disproportionately quick recovery for something that felt quite dramatic.
I wish the common cold was, uh, as fast to recover.
Jen Oliver: Yeah, imagine.
Chris Smith: I know.
That'd be good.
But yeah, the, the speed of recovery, um, is actually one of the most telling
things about what's going on, and it's a clue that we'll come back to
once we've unpacked the mechanism.
Jen Oliver: So how do they actually start?
It's got a fancy name.
As do a lot of things paraesthesia, which is an umbrella term for
any abnormal skin sensation without an obvious external cause.
But the everyday kind of pins and needles we get from being in certain
positions is really a circulation story as much as it is a nerve story.
Matt Edmundson: That's quite interesting, isn't it?
I, I, I'd always thought this was a nerve thing.
Mm. Um, so the circulation angle.
Uh, it's gonna help me reframe it, I guess.
Chris Smith: Yeah.
And they are genuinely, um, inseparable.
So nerves are extraordinarily demanding structures and they rely
on a continuous, uninterrupted blood flow to function properly.
So the everyday positional kind of pins and needles comes down.
Two things happening simultaneously.
We've got mechanical compression of a nerve and a reduction in its blood supply.
Jen Oliver: Exactly.
So they basically make things worse for each other.
So the blood vessels that feed the nerve run right alongside it.
So when you squeeze the nerve, you're actually pinching its
fuel line at the same time.
Matt Edmundson: So a nerve under pressure then isn't just physically
squashed, it's also being cut off from what it needs to function.
Chris Smith: That's exactly it.
And a nerve being deprived doesn't simply go quiet.
It starts sending these kind of chaotic, unpredictable signals
rather than the orderly ones that your brain is used to receiving.
Jen Oliver: And that chaotic firing is what the brain interprets as
something strange and unfamiliar.
It can't make sense of the signal.
So rather than recognizing it as an nerve under pressure, it
registers, uh, registers it as something that needs attention.
Matt Edmundson: Right.
So when your leg falls asleep, then it's not actually asleep.
It's not actually silent.
It's more like a radio that's kind of picked up interference
instead of the actual station.
Chris Smith: Yeah, that interference analogy is a good one.
In fact, we should call you captain analogy.
Sure,
Matt Edmundson: yeah, yeah, yeah.
Chris Smith: If I'm captain, kind of sensible or Captain MythBuster
Matt Edmundson: MythBuster,
Jen Oliver: I,
I still need one.
I still need a title.
Matt Edmundson: Madam MythBuster, wasn't it?
I can't
Jen Oliver: remember.
Yeah, I wasn't keyed on
Matt Edmundson: that.
Oh, yeah.
We need a better one.
Chris Smith: Um, so I've, I've lost my train.
We, we'll talk about Oh yeah.
Your analogy of, um, interference.
And it is a good one because, um, what determines the specific character of
that buzz that you get comes down to which nerve fibers are affected and
in what order, because not all fibers respond to compression the same.
Jen Oliver: So to add to that, so the big myelinated ones, they're
called the AB to fibers and they handle regular light touches.
They're the most sensitive to being squeeze because they need the most energy.
So they're the first to shut down essentially when the blood flow drops.
Matt Edmundson: So the fibers whose entire job is to tell your brain
everything is fine, or the first ones to check out under pressure.
So is this a bit of a design flaw?
Chris Smith: Well, yeah, I think, I think it's a fair point.
And when, um, when those large fibers go offline, the brain stops receiving
the usual reassuring touch signals and in the absence of that normal
input, its interpretation of what's happening to that limb shifts entirely.
Jen Oliver: So you then left with the smaller fibers, the A delta and the C
fibers that carry pain and temperature signals, and they're more resilient,
so they keep firing even when the larger fibers have already dropped out.
Matt Edmundson: Yeah, so your brain is getting the something run signals.
Without the, actually it's fine signals to balance them out.
It's like the alarm is going off, uh, without the all clear.
Chris Smith: Yep.
Captain analogy.
Thank you very much.
But yeah, that alarm without the all clear framing explains why there's kind of often
a distinct sequence of the experience.
So many people notice the area goes numb first before that tingling begins.
And that numbness is the.
A B to fibers that gem mentioned going quiet.
The tingling that follows is what happens when those smaller fibers
are left broadcasting on their own.
Jen Oliver: And that's a really, it's a really useful distinction 'cause
many people assume that the numbness and tingling are the same thing, but
that actually two stages of the same process just happening in sequence.
Matt Edmundson: Yeah.
So you go through the numbness on the way in and then the tingling on the
way back out and those two feelings.
Are basically the backends of the whole event, right?
Mm-hmm.
Chris Smith: Exactly right.
And, and here's the find that I find genuinely fascinating.
Okay?
Make of that what you will geek the tingling itself,
Matt Edmundson: captain geek,
Chris Smith: the tingling doesn't happen while the nerve is compressed.
It happens when the pressure is released.
And the blood flow is rushing back in,
Jen Oliver: and that's the key part.
As the circulation returns, the NA near fibers, they start coming back
online, but it's not all at once and it's not in a coordinated way.
So different fibers recover at different speeds, which causes them to
fire chaotically as they reactivate.
Matt Edmundson: So the pins and needles are not, then the
injury is what I'm hearing.
They're the recovery.
So you feel the worst of it when you are actually getting better.
Which kind of reframes the experience.
Chris Smith: Yeah, absolutely.
And picking up on that recovery idea, the reason the tingling seems to travel
that kind of crawling feeling, moving up your foot or along your arm is because
it's following the actual nerve path as sections progressively come back online
Jen Oliver: and different fibers also have different recovery thresholds,
which is why the sensation shifts from like a burning to a buzzing to something
more normal over the course of a few minutes, it's staged and it's sequential.
Matt Edmundson: So your nervous system is doing a staged restart section by section,
and those uncomfortable feelings are just.
In my terminology, the loading screen.
Chris Smith: Absolutely.
And it explains that kind of quick, I think you said few minute or two minute
recovery that you, Matt mentioned right at the top, the nerve was never
damaged, it was just temporarily offline.
And once that blood supply is restored, the hardware is
intact and recovery is rapid.
Jen Oliver: And that distinction between positional, parathesia and
nerve damage is key because like a brief compression that resolves cleanly,
but a prolonged or repeated pressure.
That can cause structural changes over time.
Matt Edmundson: Yeah.
So there's a meaningful difference, isn't there, between sitting awkwardly
for 20 minutes, which I do do, and then doing the same thing every
day for years, which I may do.
Um, and I guess the body can handle the occasional mistake.
It's that sustained habit that changes things.
Mm,
Chris Smith: it is.
But to look at.
From another angle, this is all fine unless the cause isn't positional at all.
So pins and needles can also be one of the first signals of an
underlying health condition, and it's worth knowing what to look for.
Jen Oliver: Yeah, so diabetes is probably the most clinically significant cause,
um, having persistently high blood sugar that damages the small vessels that
supply peripheral nerves, the same ones that we've been chatting about and that
eventually causes peripheral neuropathy.
You know, chronic tingling and numbness, and that usually
starts in the hands and the feet.
Matt Edmundson: Yeah.
So it's the same mechanism, right?
Nerves not getting enough blood.
But this time it's chronic rather than temporary.
Chris Smith: It is.
And um, the scale of it is striking.
So research from diabetes uk um, estimates that around 50% of people with diabetes
develop some degree of peripheral neuropathy, making it one of the most
common causes of, uh, complications of the condition of diabetes.
Jen Oliver: And that statistical alone is a good reason to take persistent,
unprovoked tingling seriously.
Um, another cause vitamin B12 deficiency.
Um, is a co a cause that's often underdiagnosed, so B12 that maintains
the myelin sheath, the protective coating around your nerve fibers that lets
signals travel quickly and accurately,
Matt Edmundson: which is particularly relevant for anyone who's on a plant-based
diet because B12 is entirely, uh, well, almost entirely absent, isn't
it, from, um, non-animal food sources.
So it's not a deficiency that's gonna correct itself without
kind of deliberate action.
Chris Smith: Exactly.
It's so important.
And, um, without adequate B12, that myelin progressively degrades with one
of the earliest symptoms typically being tingling or numbness in the extremity.
So the hands and the feet, but it becomes more serious,
neurological issues can develop.
Jen Oliver: But what makes B12 tricky is that the body stores a large
reserve of it, and the depletion happens gradually over months or years.
So by the time someone's symptoms appear, they may actually be really deficient.
Matt Edmundson: Yeah, so persistent pins and needles then in your hands could
be your body's first clear, noticeable signal of a nutritional gap that's been
quietly building up for a long time, and it's probably worth taking seriously.
Yeah.
Chris Smith: Yeah, it really is.
And that's why regular B12 monitoring for all of us is, uh, so important.
And it's particularly for those on long-term, um, diabetes
medications like metformin, which interferes with B12 absorption.
Jen Oliver: And magnesium.
That's another one that's probably worth us flagging that directly affects nerve
signal transmission and low magnesium.
It makes the nerves more excitable, which produces spontaneous tingling,
especially again in the hands and feet.
Matt Edmundson: And magnesium is one of the most consistently under consume
minerals in our modern day diet, isn't it?
Mm-hmm.
So it's another case where the nutritional gap might be showing up as a symptom.
Um, that seems to be completely unrelated to food.
Chris Smith: Uh, it's a really good point.
And um, carpal tunnel syndrome is another very common cause, and it follows the same
compression logic we've already laid out.
So in this case, the median nerve gets compressed as it passes
through a narrow channel in the wrist producing this kind of.
Tingling, uh, specifically in the thumb, the index finger and the middle fingers.
Jen Oliver: But what's worth adding to that is that carpal tunnel, it isn't just
a risk problem 'cause it's a nerve pathway problem, and the median nerve that you
mentioned that runs from the neck all the way to the fingertips, and compression
anywhere along that root can contribute to symptoms that you feel in your hand,
Matt Edmundson: which explains why it's, I guess, so widespread now.
Right?
Um, if you're at a keyboard, six to eight hours a day, or 10 to 12
hours a day, depending on your job.
Um, if you've got your wrist sort of bent, slightly out position, the nerve is
sort of under this low level compression, isn't it, for most of your working life.
And I, I figure it's eventually gonna stop tolerating that.
Mm-hmm.
Chris Smith: And with this whole topic of pins and needles, there's one more cause
that genuinely catches people off guard.
And that's anxiety.
So when we're anxious, we tend to over breathe often, quite subtly,
you know, without even noticing.
But this lowers the CO2 levels in our blood.
Jen Oliver: Yeah.
And that CO2 drop, it's got direct physiological consequence, so it
changes the blood pH, it lowers blood calcium, and that increases
the peripheral nerve excitability.
So that means the nerves start firing more spontaneously, producing
tingling, particularly in the hands and around your mouth.
Matt Edmundson: Mm-hmm.
So the tingling you get during an anxious moment that isn't
imagined, it's a real measurable.
Um, physiological response to a breathing change, right?
Jen Oliver: Mm.
Chris Smith: Yeah.
And, and the evidence for it is, um, surprisingly direct.
So studies using controlled hyperventilation.
Can reliably reproduce pins and needles in healthy subject within two to three
minutes, which shows exactly how quickly CO2 changes affect that nerve function.
Jen Oliver: But the good news is that, you know, slow control breathing
during an anxious episode, it doesn't just calm you psychologically, it
actively corrects that CO2 imbalance.
So that's triggering the nerves, which is why the tingling fades as you
breathe more slowly and gain control.
Matt Edmundson: Yeah, so there's a specific physiological loop
at play here, isn't there?
That we can see.
You've got anxiety, which triggers shallow breathing.
Mm-hmm.
Um, which then drops the CO2 levels, which then makes.
Um, nerves, fire spontaneously, which feels alarming, which
can then deepen the anxiety.
Mm-hmm.
Uh, and knowing what's happening I think is a good way to help break that loop.
Jen Oliver: Yeah, yeah,
Chris Smith: totally.
And, um, building on that, so brief pins and needles that go away as
soon as you move are totally normal.
So the good news is that's exactly what most people experience rather than
something kind of more serious behind it.
Matt Edmundson: Yeah.
Fascinating.
I mean, the practical rule I'm taking from all of this.
If change in position fixes it, it's almost certainly mechanical.
Mm-hmm.
If movement makes no difference at all, um, that's the signal
probably to go get it looked at.
Jen Oliver: Exactly.
And the patterns worth flagging to a doctor are persistent,
tingling in the same location without a positional explanation.
You know, tingling that comes alongside muscle weakness or symptoms that are
consistently worse at night when you haven't even been in an unusual position.
Chris Smith: Yeah, and beyond those, I think any sudden onset
of numbness or tingling in.
You know, one side of the body.
Yeah.
Especially alongside the, um, like facial drooping, slurred speech or arm weakness
that needs emergency attention because it can indicate a stroke or a TIA.
Mm-hmm.
Matt Edmundson: Yeah.
And that presentation is clearly different right from gradual,
uh, from the gradual bilateral.
I've been sitting on the floor in a weird position way too long.
Mm. Um, it's sudden it's one-sided and accompanied by other things that feel.
Unmistakably wrong.
Jen Oliver: Yeah.
So as Matt says, the vast majority of pins and needles is your body doing
exactly what it should be, but it's a sensation worth staying curious about
rather than always dismissing it.
Chris Smith: Yep, it is.
And so for everyday positional kind of pins and needles, gentle movement
is the most effective response because it encourages that blood flow.
It speeds up that nerve recovery process that we described earlier.
Jen Oliver: So here's a fun fact for you.
There is
Matt Edmundson: F I've figured out your name.
Jen Oliver: Go on.
Matt Edmundson: Fun fact, Jenny.
Jen Oliver: So you two get capped in something and I get you
Matt Edmundson: can be captain in.
Fun fact.
Jen Oliver: Okay.
Okay.
I thought I was just gonna get fun.
Fact, Jenny.
Okay, so yeah, so here's a fun fact.
There is no evident.
For the vigorous shaking is more effective than gentle movement
to get rid of pins and needles.
So the nerve just needs circulation restored and a bit of time to resequence
its firing, which happens naturally.
Matt Edmundson: Well, thank you, uh, captain from fact because I am the
person that violently flex my hands trying to get, you know, like I'm
trying to launch it off my wrist.
Uh, and I figure I'm not the only one that's, uh, that's done that.
Jen Oliver: No, no, no,
Chris Smith: Yeah, there's genuinely no need for the kind of vigorous action.
Um, gentle is enough, but for recurrent carpal tunnel symptoms,
specifically wrist splints worn at night have solid clinical evidence.
They prevent the risk from flexing during sleep, which is when
compression tends to be at its worst.
Jen Oliver: And for the anxiety related kind, slow diaphragmatic breathing is
probably the most direct intervention.
So you are actively restoring CO2 levels and reducing the nerve
excitability, not just managing how you feel about the situation.
Matt Edmundson: So the box breathing that gets recommended for anxiety is
a direct physiological reason why it works specifically for the tingling.
Jen Oliver: Mm-hmm.
Chris Smith: Yeah.
And for a lot of people.
If you think of kind of office workers, the most useful long-term habit is
actually about posture and screen setup.
So keeping your wrists in a neutral position during keyboard work.
Taking regular breaks from sustained positions that removes
the low level compression that accumulates across that working day.
Jen Oliver: Well, if you get chronic or recurring pins and needles, try and focus
on root causes like posture, nutrients, blood sugar, rather than quick fixes.
Matt Edmundson: Yeah, so the long term answer isn't what you do when it happens.
It's the conditions you're creating day in, day out that determine how
often it shows up in the first place.
Jen Oliver: And that connects back to a lot of ground we've covered before,
like B12, vitamin D, Omega-3, magnesium.
These all affect neurological function in different ways, and pins and
needles is just another place where those gaps surface as physical signals
before anything more serious develops.
Chris Smith: Yeah, that's a really important thread and blood flow.
Quality runs through all of it.
So whether it's cardiovascular health, uh, brain function, or
peripheral nerve health, the quality of circulation fundamentally shapes
how the whole system performs.
Matt Edmundson: Yeah, and it also ties back to the brain fog episode where nerves
under sustained stress and nutrients aren't reaching where they need to go.
The body uses these sort of sensations like pins and needles to flag something.
It can't communicate in any other way.
Jen Oliver: And I keep coming right back to what Chris said at the start,
that the pins and needles themselves are the recovery, not the damage.
So the uncomfortable sensation is actually proof that your
nervous system is doing its job.
Chris Smith: Yeah, and it's a good reminder that the body's warning
systems, uh, signals are often the same as its repair signals.
So the discomfort and the correction are the same event happening at the same time.
Matt Edmundson: Your nervous system, your nervous system, staging a full.
Uh, protest turns out to be working exactly as intended,
which makes it considerably easier to live with that knowledge.
Jen Oliver: So that's why the next time that familiar buzz starts
working it's way up your foot, you'll know exactly what's happening.
That's not a problem.
That's the recovery already underway.
Yeah.
Matt Edmundson: Your nervous system is doing a full-time reboot in real time.
Jen Oliver: So that's it for this week.
Hit subscribe and drop as a comment with whatever question
you'd like us to explore next.
Thanks for geeking out with us, but for now, that's it from me.
Matt Edmundson: That's it from me.
Chris Smith: And that's it from me.
Jen Oliver: Bye for now.