- Stubbing your toe hurts so much because you’re slamming a tiny surface with a force equal to 2-3 times your bodyweight.
- Then a bundle of nerve endings called nociceptors fire a danger signal to your brain.
- Although it’s not pleasant, this pain might have helped your ancestors step carefully and avoid injury and infection.
Following is a transcript of the video.
Stubbing your toe hurts. It’s right up there with paper cuts and chapped lips. Annoying, minor injuries that hurt way more than they have any right to. But it turns out, there’s a good reason why stubbing your toe hurts so much.
When you stub your toe, you’re slamming it with a force equal to 2-3 times your body weight. That’s about the same force as a karate punch! And since your toe has a tiny surface area, that force can’t spread out. So the pain stays concentrated at the point of impact.
It’s the same reason it hurts more to step on the tiny, pointy end of a thumbtack than the wider, blunt end. But you don’t just feel an immediate shock like when you step on a thumbtack. There’s that aching throb that comes after. That’s because when you stub your toe, you’re actually hitting a bundle of special nerve endings called nociceptors. They all fire at once, blaring a danger signal.
But some signals travel faster than others. The faster, A-delta nociceptors fire the first wave of signal, which races at 20 m/s up thousands of densely-bundled nerve fibres and ultimately to your brain. That causes the sharp, sudden pain you feel at the moment of impact. But some nerve fibres called C nociceptors send a slower signal at only 2 m/s. So after a moment’s delay, a second wave of pain signals reach your brain. That’s the dull throbbing that lingers on.
You can find nociceptors all over your body, from your eyes to your bladder. But they’re concentrated at the highest densities in parts of your body you use to explore your environment, like your fingertips, and lips. That’s why accidents like paper cuts and chapped lips can also hurt more than they seem like they should. Now, your toe isn’t packed with as many nociceptors as your fingertips. But since there’s not much in the way of fat padding to cushion the blow it’s easy to set those unprotected nociceptors off. And that’s no coincidence.
Researchers suspect the pain we feel from mishaps like a stubbed toe might’ve saved our ancestors’ lives. Back before antibiotics, even the tiniest cut could mean a deadly infection. And feet, which were constantly in contact with dirty, bacteria-infested surfaces were particularly vulnerable. So people who had extra- sensitive feet might’ve been more careful about where they stepped. As a result, they’d be less likely to get infections and would live to pass on their genes.
So the next time you collapse to the floor, cradling your aching toe you can thank your great great great great great great grandpa for the privilege.
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