Why is it sometimes less sleep makes you feel more replenished and energetic than more sleep?
In: 4
As others have said, because of sleep cycles!
When you are asleep, [your brain goes through ~1.5-hour cycles of activity](https://www.thegreatcoursesdaily.com/wp-content/uploads/2019/09/shutterstock_1198377799.jpg). In each cycle there’s increasing depth of sleep (aka lowering level of brain activity), punctuated by periods of much lighter (“REM”) sleep.
Here’s the key: **How rested you feel depends on what stage of the cycle you are woken up from.**
When you wake up naturally (the far right of my linked pic), you go from REM (lightest sleep) to awake. If your alarm goes of during a light (Stage 1) part of the cycle, that’s good too. If your alarm goes off and wakes you from the deepest part of the cycle (Stage 3 or especially 4), that’s when you feel exhausted all day, no matter how many hours you slept before the bad wake-up. In your specific example (waking up naturally after 5 hours and feeling good), you probably woke up on your own during the second Stage-1 portion. That takes about 4.5h of actual sleep, so ~5h after going to bed sounds about right.
Consequences of this information:
1. Sleeping in multiples of 1.5 hours is best, if you can. There are apps and websites to time it for you and set off your alarm at the optimal time closest to when you tell it you *need* to be awake for.
2. Failing that, always sleep for the same amount of hours. *Ideally* a sleep cycle is 1.5 hours, but if it’s always getting interrupted, your body is quite good at changing its sleep cycle pattern to fit the available time. But it can only do that if you have regular sleep hours! So like, if you always sleep from midnight to 5 AM, your body will make an whole number of complete cycles fit those 5 hours.
[Source: University degree with an undergrad specialization in Cognitive Neuroscience]
Latest Answers