How can sitting there and thinking wear you out?

坐在那裡思考怎麼會讓你疲憊不堪？

Hey Brainiacs, Julia here for DNews.

嘿，Brainiacs，我是 DNews 的 Julia。

Have you ever been really tired after spending all day sitting around at school?

在學校坐了一整天，你是否感到過非常疲憊？

How can you be so exhausted from literally just sitting all day?

你怎麼能整天坐著就累成這樣？

Why is learning so tiring?

學習為什麼這麼累？

Well, let's start with the body's energy usage.

我們先從人體的能量消耗說起。

About 30% of the calories you eat go towards maintaining your current muscle mass.

你攝取的大約 30% 的卡路里用於維持當前的肌肉質量。

While our brain only makes up 2% of your body weight, it gobbles up 20% of the energy you take in.

雖然我們的大腦只佔體重的 2%，但它卻消耗了你攝取的 20% 的能量。

One study published in Proceedings of the National Academy of Sciences USA found that 2/3s of the energy the brain uses goes to the firing of cells.

美國國家科學院院刊上發表的一項研究發現，大腦使用的能量有 2/3 用於細胞的放電。

But the other third, is basically just brain maintenance.

但另外三分之一基本上只是大腦維護。

So where does that energy come from?

那麼，能量從何而來？

Most of the energy the brain eats up is in the form of glucose from the things we eat.

大腦消耗的大部分能量是以我們吃的食物中的葡萄糖的形式存在的。

When neurons in the brain fire, they need extra oxygen and glucose from nearby capillaries.

當大腦中的神經元放電時，它們需要來自附近毛細血管的額外氧氣和葡萄糖。

So scientists think that when performing a difficult mental task, the neurons would eat up more glucose.

因此科學家認為，當執行一項困難的腦力任務時，神經元會消耗更多的葡萄糖。

And so there'd be less glucose in the bloodstream if you'd measure it after something like a tiring test.

因此，如果你在進行疲勞測試後測量血糖，血液中的葡萄糖就會減少。

And that is what some studies show.

一些研究也表明了這一點。

Another study published in the journal Physiology Behavior found that there was less blood glucose in the bloodstream, which the researchers thought was linked to neurons firing on all cylinders.

《生理行為學》期刊發表的另一項研究發現，血液中的血糖含量較低，研究人員認為這與神經元的活躍有關。

Another more recent study published in Human Factors: The Journal of the Human Factors and Ergonomics Society found that people get more exhausted when exerting both physical and mental faculties than when just simply working out.

另一項最近發表在《人為因素：人為因素與人體工學雜誌》上的研究發現，人們在發揮身體和精神能力時比單純運動時更容易感到疲憊。

The researchers specifically noted that when performing both physical and mental tasks, there was strong activity in the prefrontal cortex and there was lower blood oxygen levels in the PFC after a combined physical and mental task than when just doing physical work.

研究人員特別指出，當同時執行體力和腦力任務時，前額葉皮質會出現強烈的活動，在執行體力和腦力任務時，前額葉皮質的血氧水平會比只進行體力工作時更低。

So following that line of thought, eating foods high in glucose should improve mental performance.

因此，按照這個思路，吃高葡萄糖食物應該可以改善精神表現。

One review published in the European Journal of Pharmacology found that glucose can improve memory, but it really depends on the dose and the person.

《歐洲藥理學雜誌》發表的一篇評論發現，葡萄糖可以改善記憶力，但這實際上取決於劑量和個人。

So there is something about mental tasks that makes our brains work a little harder and take up a little more glucose.

因此，腦力任務中的某些因素會讓我們的大腦更努力工作，並消耗更多的葡萄糖。

But why does it actually make us tired?

但為什麼它實際上會讓我們感到疲倦呢？

Well, results are mixed.

結果各有不同。

One small study published in the journal Psychosomatic Medicine found that people who just completed memorization and attention tests ate 200 more calories than those who just relaxed.

《心身醫學》雜誌上發表的一項小型研究發現，剛完成記憶力和注意力測試的人比剛放鬆的人多攝取 200 卡路里。

But it might be more than just brain drain.

但這可能不僅僅是大腦疲勞造成的。

One scientist, Claude Messier of the University of Ottawas, thinks maybe it's just stress, that those students were just stress eating, which is a very real thing.

渥太華大學的一位科學家 Claude Messier 認為，也許這只是壓力，那些學生只是在壓力下進食，這是非常真實的事情。

So while test taking might be zapping your energy, maybe it's the classroom you're in.

因此，雖然考試可能會消耗你的精力，但也許是因為你身處的教室造成的。

Matt Lieberman explains how carbon dioxide in the classroom might make for slower brains.

Matt Lieberman 解釋了教室中的二氧化碳如何導致大腦變慢。

It turns out even levels as low as 1,000 parts per million can reduce the brain's ability to focus and function properly.

事實證明，即使濃度低至百萬分之 1,000，也會降低大腦集中注意力和正常運作的能力。

And considering that we produce carbon dioxide every time we exhale, that's a big old problem.

考慮到我們每次呼氣時都會產生二氧化碳，這是一個大問題。

So what was the last time you felt tired after a test?

那麼你上一次在考試後感到疲倦是什麼時候？

Tell us about it down in the comments below.

請在下面的留言區中告訴我們。

Don't forget to hit those like and subscribe buttons to keep coming back to DNews. We have new episodes every day of the week.

不要忘記按讚和訂閱以繼續返回 DNews。 我們每週都有新影片。