You wake up at 7 a.m. and you feel refreshed.

你早上 7 點鐘起床時，清神飽滿。

You decide to sleep in for 2 more hours, and when you wake up at 9 a.m., you feel like crap.

你決定多睡個 2 小時，但在 9 點起床時，卻感覺糟透了。

How come those extra 2 hours, instead of energizing you, they actually made you feel worse?

為什麼那多出來的 2 個小時，讓你感覺更糟，而不是更有精神呢？

Well, first we need to understand how our sleep works, so we can figure out how to manipulate it and wake up alert and refreshed.

這個嘛，我們首先需要睡眠的原理，才能知道怎麼運用它，讓我們早上起床精神飽滿有警覺性。

Our sleep is made of three stages.

我們的睡眠由三個階段組成。

The first stage is called "light sleep."

第一階段被稱為「淺層睡眠」。

This is right after you go to sleep.

這發生在你剛入睡時。

Any sudden noises may awake you, and people often report that they feel awaken when sleeping in this stage.

任何突然的聲響都可能吵醒你，很多人也回報他們在這個睡眠階段感覺自己是清醒的。

The second stage is "deep sleep" or "Delta Phase."

這二個階段是「深層睡眠」或「非快速動眼期」。

This is where we sleep most deeply.

這是我們睡得最熟的時候。

The last stage is called "REM Sleep" or "rapid eye movement sleep."

最後一個階段是「快速動眼睡眠（REM 睡眠）」。

This is the stage where we dream.

我們是在這個階段做夢。

Our eyes dart back and forth beneath closed lids and our muscles temporarily shut down to prevent us from acting out dreams.

我們的眼睛會眼皮下左右移動，而我們的肌肉會暫時停止活動，預防我們的身體反應出夢境。

After the REM sleep, we enter the first stage, light sleep, and the cycle repeats.

經過 REM 睡眠後，我們會回到第一階段的淺層睡眠，然後重複這個週期。

The whole cycle takes around 90 minutes to complete.

整個週期大約 90 分鐘會完成。

So if you were sleeping for 9 hours, that means you've been through 6 sleep cycles.

所以如果你睡了 9 個小時，代表你經歷了 6 個睡眠週期。

The reason we feel groggy and tired, is when we wake up in the middle of the cycle.

我們覺得昏沉又疲倦的原因是因為我們在週期中醒來。

So if you want to feel refreshed, find out when you want to be awake, then count backwards in 90-minute blocks.

所以如果你想要感到有精神，決定你要起床的時間，然後以 90 分鐘的間隔往後推算。

For example, if you need to wake up at 7 a.m., you should aim to be asleep at 11:30 p.m.

舉例來說，如果需要在早上 7 點起床，你應該以晚上 11 點 30 分入睡為目標。

That's 7 and a half hours of sleep, or 5 cycles. Of course, you can plan for 6 or 9 hours of sleep, but that depends on you.

這樣是 7 個半小時，也就是 5 個週期的睡眠，當然你也可以計畫睡個 6 小時或 9 小時，一切取決於你。

And also, the common belief that we should sleep for 8 hours per night is actually wrong, because it does not align with our sleep cycles.

此外，一個晚上需要睡 8 小時這個常見的說法其實是不對的，因為它並不符合睡眠週期。

So, if you want to never again feel tired or groggy in the morning, and if you want to wake up alert and refreshed, keep in mind the 90-minute rule.

所以你如果不想在起床時感到又累又昏，希望可以神采奕奕的話，要牢記這 90 分鐘原則。

Anyway, don't forget to subscribe, and thanks for watching.

總之，別忘了訂閱，感謝收看。