午睡不要超过25分钟，也别趴桌上睡！Power nap了解一下

The ideal nap length, according to scientists, is 20 to 25 minutes. Any longer and you’ll fall into a deeper sleep cycle, which lasts for about 90 minutes. This means when you wake up you will experience “sleep inertia”, or grogginess.

inertia /ɪˈnɜːʃə/：惰性；缺乏活力

A power nap, also known as a Stage 2 nap, is a short slumber of 20 minutes or less which terminates before the occurrence of deep slow-wave sleep (SWS), intended to quickly revitalize the napper.

Salvador Dalí, in his 50 Secrets of Magic Craftsmanship for aspiring painters, outlined tips for the one-second micro-nap, including sitting upright, key in hand and upturned plate beneath. Once asleep, the key will drop and the ensuing clang ensures instant revival. Albert Einstein deployed a similar technique, using a spoon or pencil instead of a key.

Exceptions to this include essential naps when sick, which are often longer because our bodies require more sleep when dealing with an illness. Also, fulfillment naps in children should not be limited to 20 minutes, as children have a higher sleep requirement than adults.

If you nap too late in the day it’s a bit like snacking before main meal, it just takes the edge off your sleep hunger at night.