It's right up there with paper cuts and chapped lips, annoying minor injuries that hurt way more than they have any right to.

程度與紙片割手與嘴唇龜裂相當。這些小傷造成的痛達到人神共憤的境界。

But it turns out there's a good reason why stubbing your toe hurts so much.

不過事實上，踢到腳趾這麼痛是非常有原因的。

When you stub your toe, you're slamming it with a force equal to two to three times your body weight.

踢到腳趾的當下，你相當於用體重兩到三倍的力量踢腳趾。

That's about the same force as a karate punch.

差不多等於空手道的一拳。

And since your toe has a tiny surface area, that force can't be spread out, so the pain stays concentrated at the point of impact.

由於腳趾的表面積很小而力量不能分散，因此疼痛就集中在受到衝擊的那一點。

It's the same reason it hurts so much more to step on the tiny, pointy end of a thumbtack than the wider, blunt end.

同樣道理，踩在圖釘小又尖銳的那端時，劇痛程度遠勝踩到較寬又鈍的那頭。

But you don't just feel the immediate shock like when you step on a thumbtack.

然而，你感受到的不僅是當下踩到圖釘而立馬反應的衝擊。

There's that aching throb that comes after.

還有隨之而來的抽痛。

That's because when you stub your toe, you're actually hitting a bundle of special nerve endings called nociceptors.

這是因為當你踢到腳趾時，其實擊中的正是一堆特別的神經末梢—傷害受器。

They all fire at once, blaring a danger signal.

它們立馬發出刺耳的警訊。

But some signals travel faster than others.

可是有些信號傳送速度較快。

The faster A-delta nociceptors fire the first wave of signal.

A-delta 傷害受器 (神經纖維) 發出第一波的信號。

Which races at 20 meters per second of thousands of densely bundled nerve fibers, and ultimately to your brain.

在大量密集的神經纖維裡以每秒 20 公尺的速度全速前進，最終進入腦部。

That causes the sharp, sudden pain you feel at the moment of impact.

在受到衝擊的當下造成突然的刺痛。

But some nerve fibers called C nociceptors send a slower signal at only 2 meters per second.

不過有些叫作 C 傷害受器的神經纖維，其送出的信號較慢，速度僅為每秒 2 公尺。

So after a moment's delay, the second wave of pain signals reach your brain.

所以短暫的延遲後，第二波的疼痛信號到達腦部了。

That's the dull throbbing that lingers on.

其停留體內並隱隱作痛。

You can find nociceptors all over your body from your eyes to your bladder.

全身從眼睛到膀胱都可找到傷害受器的蹤跡。

But they're concentrated at the highest densities in parts of your body that you use to explore your environment.

但它們高密度地聚集於探索環境的身體部位。

Like your fingertips and your lips.

像是指尖和嘴唇。

That's why accidents like paper cuts and chapped lips can also hurt more than they seem like they should.

這就是為何紙片割手與嘴唇龜裂的痛似乎被放大了好幾倍。

Now, your toe isn't packed with as many nociceptors as your fingertips.

雖然你腳趾上的傷害受器沒有指尖的多。

But since there's not much in the way of padding to cushion the blow, it's easy to set those unprotected nociceptors off.

但由於沒有什麼墊材類的東西可以減少衝擊，未受保護的傷害受器便容易被觸發。

And that's no coincidence.

這並非巧合。

Researchers suspect the pain that we feel from mishaps like a stubbed toe might have even saved our ancestors' lives.

研究人員懷疑，我們腳趾踢到的痛，可能甚至拯救了祖先的性命。

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.

抗生素問世前，即使是最小的傷口都可能造成致命的感染，而腳特別脆弱，因為常常與骯髒又充滿細菌的地面接觸。

So the people who had extra-sensitive feet might have been more careful about where they stepped.

所以腳部特別敏感的人，就可能特別留意腳下所踩之物。

As a result, they'd be less likely to get infections and would live to pass on their genes.

因此，他們感染的機率可能較小，進而繁衍後代，將基因留存。

So the next time that you collapse on the floor cradling your aching toe...

所以下次你痛得倒在地下輕抱著腳趾時...

You can thank your great-great-great-great-great-great-great-great-great-great-great-grandpa for the privilege.

你可以感謝你曾曾曾曾曾曾曾曾曾曾曾祖父所賜的恩典。