Why do your knuckles pop? - Eleanor Nelsen

為什麼你的指關節會突然發出啪的聲音？- 埃莉諾．內爾森

譯者: Yeh Andy 審譯者: Linus Chen

What's that sound?

那是什麼聲音？

Depending on whom you ask,

這問題取決於你問誰，

the crackle of popping joints is either the sound of sweet relief

關節突然啪的一聲， 不是放鬆的聲音

or the noxious tones of a stomach-turning habit.

就是有反胃時 所發出的討厭聲音。

Really, though. What's that sound?

然而，實際上，那到底是什麼聲音？

I mean, why does bending your joints in a certain way make them pop like that?

我的意思是，為什麼只要以某種方式 彎曲指關節就能讓它們發出這樣的聲響？

Scientists have offered several explanations,

科學家們已經提出幾種解釋，

including rapidly stretching ligaments,

包括快速的拉伸的韌帶，

and in severe cases, actual bones grinding against each other.

以及骨頭彼此之間相互摩擦的極端例子。

But the most common explanation

但是，對於為什麼伸展關節會發出

for why your stretched-out joints sound like bubbles popping

像泡泡破掉的聲音最常見的解釋

is that, well, there are bubbles in there.

就是，這裡是有泡泡的。

The joints in your fingers are the easiest ones to crack,

手指關節是最容易發出啪啪聲的，

but many people also crack the joints between vertebrae in their neck and back,

但有很多人的脖子和後背 這段脊椎之間，也會發出啪的聲音，

and even their hips, wrists, shoulders and so on.

甚至他們的臀部，手腕，肩膀等也都會。

All these joints are synovial joints,

這些關節都是滑膜關節，

and they're the most flexible ones in your body.

而且他們在你的身體裡是最有彈性的。

The space between the two bones is filled with a viscous liquid,

在骨頭和骨頭之間充滿著關節液，

synovial fluid, which contains long, lubricating molecules,

這些關節液包含有 長的、具潤滑作用的分子，

like hyaluronic acid and lubricin.

像是玻尿酸和潤滑素。

Synovial fluid is more or less the texture of egg yolk

關節液某種程度上就像是雞蛋的蛋黃，

and its primary purpose is to cushion the bones

其主要目的是為了緩和 骨頭和骨頭彼此的撞擊

and help them glide past each other.

並幫助他們彼此滑動。

It also contains phagocytic cells

它還包含吞噬細胞，

that help clean up any bone or cartilage debris that ends up in the joint.

這有助於清理在關節間的 任何骨頭或軟骨碎片。

But the reason it's important for knuckle cracking

但對於關節發出啪聲很重要的原因

is that, like other fluids in your body,

就像身體裡的其他體液一樣，

it contains lots of dissolved gas molecules.

它含有大量溶於其中的氣體分子。

Knuckle-crackers know that to get that satisfying pop,

喜愛讓關節發出啪聲的人 知道如果要發出令他們滿意的聲響，

you stretch the joint farther than it normally goes

例如：向後彎曲你的手指

by bending your fingers backwards, for example.

就是比在正常時更進一步地伸展關節。

When you do that, the bones move away from each other.

當你這樣做時，骨頭會遠離彼此。

The space between bones gets bigger,

骨頭之間的空間變大了，

but the amount of synovial fluid stays constant.

但關節液的量保持不變。

That creates a low-pressure zone

因此產生一個低壓區

that pulls dissolved gases out of the synovial fluid,

於是就把關節液中溶解的氣體吸引出來，

just like the carbon dioxide that fizzes out of soda

就像當你打開汽水瓶蓋時，

when you twist open the cap.

二氧化碳跑出來時會起泡泡一樣。

Inside the joint, the escaping gases form a bubble with a pop.

在關節裡，氣體從破掉的氣泡中散出。

But the bubble doesn't last long.

但是，氣泡形成的時間並不長。

The surrounding fluid presses on it until it finally collapses.

周圍的流體壓力壓住它直到它破裂。

The bubble's gases scatter throughout the synovial cavity

氣泡內的氣體散佈整個滑膜腔

and slowly dissolve back into the fluid over the course of about twenty minutes,

然後在二十分鐘內緩慢地溶解回到液體中，

which is why it can take a while before you can pop the same joint again.

這就是為什麼可能需要一段時間之後， 才能再次發出啪的聲音。

Some scientists think there may actually be two pops.

有些科學家認為實際上 有可能發出兩聲啪的聲音。

One when the bubble forms, and another when it bursts.

第一聲是當氣泡形成時，另一聲則是氣泡破掉時。

Popping a joint temporarily enlarges it,

使關節發出啪啪聲會短暫地伸展身體，

which may be why dedicated knuckle-, neck- and back-crackers

這有可能是為什麼那些喜歡 指關節、脖子和背部發出啪聲的人，

say the habit makes their joints feel looser and more flexible.

覺得這樣的習慣會讓他們的關節更鬆、更靈活。

But you may have heard from a concerned relative or annoyed officemate

但是你也有可能從擔憂的親戚 或討厭的同事那邊聽到這樣的事：

that cracking your joints will give you arthritis.

讓關節發出啪聲會讓你得到關節炎。

A doctor named Donald Unger heard this, too.

有個名為Donald Unger的醫生也聽到了這種說法

So, determined to disprove his mother's warnings,

所以他決定要證明他母親的警告是錯的

he cracked the knuckles of his left hand repeatedly for 50 years,

50年來，他一再地讓左指關節發出啪聲

while the right-hand knuckles went unpopped.

而右手指關節不發出啪啪聲。

36,500 cracks later, both hands were arthritis-free.

在啪了36500次後，兩隻手都沒有得到關節炎

For this selfless act of devotion to science,

這個在科學上無私的奉獻，

Dr. Unger received an Ig Nobel Prize,

Unger醫師得到了搞笑諾貝爾獎，

a parody of the Nobel Prize that recognizes wacky,

這是諾貝爾獎的滑稽模仿作品，被認定是古怪的、

but weirdly fascinating, scientific accomplishments.

但是卻迷人，在科學上有成就的一件蠢事。

Unger wrote that his results should prompt investigation into other parental beliefs,

Unger認為他的實驗結果 可以促使研究其他父母親根深蒂固的想法，

like the importance of eating spinach.

像是吃菠菜的重要性。

The jury's still out on that one.

評審委員會對這件事仍然尚未決定。

As for knuckle-cracking,

至於關節發出啪聲，

one study suggests that all that joint stretching

有研究認為那是所有關節的伸展，

and bubble bursting can cause your hands to swell

和氣泡破掉導致你的手水腫

and weaken your grip.

和減弱你的握力。

But the biggest proven danger seems to be annoying those around you.

但是實驗過程中最大的危險 似乎是這些煩人的聲音會圍著你打轉。