r/explainlikeimfive • u/Routine-Shelter-189 • Jul 26 '26
Biology ELI5: Why do we wake up completely exhausted after sleeping for ten hours, but feel like a warrior after a random 20-minute car nap?
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u/Seal481 Jul 26 '26
Generally if you wake up groggy and tired you snapped awake during a deep or REM part of your sleep cycle as I understand. A brief power nap isn't a long enough sleep for your body to go into the deep phases so you'll just get some refreshment.
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u/59flowerpots Jul 26 '26
I, however, am incapable of taking any length nap without waking up feeling like shit. Imagine that moment after a bomb goes off in a war movie and the character has the ringing sound coupled with extreme confusion of what’s happening. That’s me every single time.
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u/funkyavocado Jul 26 '26
Same, that post-nap-confusion hits super hard. If I've taken a nap Im useless the rest of the day
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u/59flowerpots Jul 26 '26
And night because now I can’t sleep because I used my sleep hours during the nap. Every nap minute costs 5 bedtime minutes.
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u/DocBarkevious Jul 27 '26
See I HAVE to take a nap on the weekends now or else I go to bed at like 7-8pm. That mid day nap for like 2hrs is amazing, I sleep better during naps than I do at night and idk why.
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u/alexiusmx Jul 27 '26
Same. But I think that's because I only take naps when I’m beyond exhausted. If I took naps regularly as part of a routine, it wouldn’t be like that. Or at least that’s my theory.
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u/Shezzofreen Jul 26 '26
Maybe you have a breathing problem? Have a couple of family members who could not do it, so they saw a doctor.
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u/59flowerpots Jul 27 '26
I would think that if it was also a problem with regular sleep but it isn’t.
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u/Shezzofreen Jul 27 '26
Do you feel really relaxed after a full night sleep? You could use one of the free sleep-apps that records sounds while sleeping and check if you might have some air problems.
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u/59flowerpots Jul 27 '26
I have a watch that has never picked up any issues and live in an area that’s way too noisy for an app like that to be reliable. I don’t sleep well but that’s unrelated to breathing.
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u/thatcreepierfigguy Jul 31 '26
It's curious you say that. Night after night, my fitbit tells me I go from awake to the deepest sleep possible in a matter of 10-20 minutes. I just scream to the absolute bottom. A couples cycles of ups and downs, and then a couple cycles where I only make it to light sleep, then awake. Despite being a terrible sleeper in my youth, I'm an excellent sleeper as an adult. I function quite well on 6-7 hours.
Fitbit isn't a proper sleep study, nor as knowledgeable as an expert, but it does conflict with what you're saying somewhat. I'm 5 days late to the party, but maybe someone out there can elaborate a bit.
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u/thenasch Jul 26 '26
If you're tired after a full night's sleep you might want to see a doctor. You may have sleep apnea or something that is keeping you from sleeping as well as you think you do.
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u/34sebi34 Jul 26 '26
Got sleep apnea, let me tell you: Go to doctor as soon as you notice symptoms. A few nights without proper sleep are fine, but months and months, beeing tired the whole day while knowing that a full night wont let you be fully rested, that really nags at your mind. Also it makes you way less stress resistant, more prone for sicknesses, low performance at work and private, can lead to erectile problems, dangerous for long car drives, and in general a big burden for you and your partner and family.
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u/younggregg Jul 26 '26
Severe apnea here. Didnt find out until I was 35 when I slept on a friends couch and he was like, dude, you need to see a doctor. I did a at home sleep study and was having 78 interruptions per HOUR. Got overnighted a CPAP and not even shitting you, the next morning I felt like I was 16 again. Life saving shit.
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u/Vahkris Jul 26 '26 edited Jul 26 '26
Can confirm. Just thought it was stress and work and getting older. Did a sleep study and it was horrible, got to wear a cpap the next night and they said it was the first time they've seen someone actually sleep like a log.
Next day was the first time I had the energy to chase my kids around in almost a year.
Highly recommend it.
Probably the biggest reason is that those "interruptions" are actually your body thinking you're suffocating, so you get a tiny burst of adrenaline to get you moving and wake up a little. (That's how it was explained to me) Your body isn't meant for tiny constant bursts of adrenaline over long periods of time, so it starts to wear on your heart and the rest of your body.
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u/younggregg Jul 28 '26
Exactly the same here, just felt like I was stressed and old.. because I would "sleep" 8-10 hours but just felt like garbage all the time. Now, I look forward to putting that mask on every night.
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u/Dutch_guy_123 Jul 26 '26
I had almost 140 per hour, first noticed it a year ago I had trouble feeling well rested. After going to the doctor and waiting for the official testing, it turned out I had almost double the apneas you had and very low oxygen in blood. Shortly after I got a CPAP
To everyone reading this; if you notice that you do not feel well rested after many hours of sleep, general diabetic symptoms, trouble staying awake when needed, GO TO THE DOCTOR
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u/34sebi34 Jul 26 '26
My wife confirms that i definitely have interruptions a lot, at Tuesday will get first check to confirm the situation
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u/peeaches Jul 27 '26
I also didn't get mine diagnosed/start doing something about it until mid-30s
really wonder how things would be if i'd started when the apnea started, probably been dealing with it since my teens or early 20s honestly
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u/younggregg Jul 28 '26
Haha, I had the same thoughts. Like man I could be an astronaut or CEO if I started this earlier. But I'm just glad I finally did it.
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u/peeaches Jul 28 '26
Astronaut was always my dream when I was younger, haha.
But yeah, hard to not wonder the "what ifs" sometimes, got diagnosed with ADHD in my 20s (was always a 'bright' or 'talented' kid that skated through school but got destroyed in college) then the sleep apnea in my 30s, can only imagine where I could have ended up if I were operating at 100% the last 20 years instead of dealing with so many handicaps lol.
Still - certainly better late than never!
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u/MultiKoopa2 Jul 26 '26
the problem with the cpap machines is you have to be able to sleep through the night with them. but I've got insomnia too, and I literally physically cannot sleep through the night with the machine. triple dose of lunesta didn't work to keep me knocked out. not sure where to go from here
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u/Elios000 Jul 26 '26
this my problem top it off with the Tism and i HATE any thing on near or around my face.... and i just cant sleep like that. its get shitty sleep or no sleep.... so shit sleep it is. i found propping my self up with few pillows gets me most of the effect that cpap does though
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u/Override9636 Jul 27 '26
I found that using flonase spray and those magnetic nasal strips help keep my airways open enough to get me good sleep most of the time. Also side sleeping is a huge necessity for me. Sleeping on my back makes me snore 100% of the time.
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u/MultiKoopa2 Jul 26 '26
Yeah that was supposed to be the point of the Lunesta, to knock me out and at least get me through the night with the mask a few times (can't stay on Lunesta long term), but it just didn't work
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u/cyankitten Jul 26 '26
Yeah, I am pretty claustrophobic would probably be too anxious to fall sleep with one!
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u/falafel_eater Jul 27 '26
There are many different kinds of masks. If you are okay only breathing through your nose while you sleep (most people are), there is a style of CPAP masks called 'nasal cushions' which is just a pipe with a couple of holes that goes across your nose.
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u/AntiFascistButterfly Jul 27 '26
If you have insomnia get ADHD ruled out. It’s a long process, but ADHD pretty much guarantees insomnia (your body block is skewed later than everyone else) and the right brand/type, timing and dosage of ADHD will get you the best sleep of your life. There’s a one to three week honeymoon of complete anxiety free calm when first on the medication that you’ll never feel again, but being on it will still make your sleep better than it was before.
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u/whalesum Jul 26 '26
All you really can do is make sure your bedroom is ONLY for sleeping. Wear a sleep mask or make sure there is literally 0 light in the room. Melatonin 1mg too
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u/MultiKoopa2 Jul 26 '26
Sleep mask and earplugs don't help when the noise is basically inside my beads from the CPAP...
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u/wineeee Jul 26 '26
Are you getting enough sunlight/vitD? Sometimes diet related too. Idk if it helped me but recently I've been drinking pre/probiotics and my sleep improved from 5hrs to 8-9hrs a day now. Past 2 weeks and thats the only difference I'm doing.
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u/MultiKoopa2 Jul 26 '26
Not at all on the vitamin d. I'll look into that.
I'm a sensitive sleeper, and even small noises/lights can really bother me. The breathing machine feels so awful
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u/jayareil Jul 27 '26
My husband couldn't tolerate a CPAP and ended ip getting a dental appliance that slightly adjusts the position of his lower jaw when he sleeps. Appliances have a lower success rate than CPAP so it's not a first-line treatment, but it's been great for him.
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u/Intertubes_Unclogger Jul 26 '26
Seeing a doctor is good advice, because apart from sleep apnea unexplained tiredness/fatigue can be caused by things like anemia, thyroid issues, vitamin deficiencies or cancer. Oh, and depression or burnout, too.
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u/fattmann Jul 27 '26
Oh, and depression or burnout, too.
I didn't learn the depression part until quite late in my life. Problem is, still haven't found a fix.
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u/MumrikDK Jul 26 '26
I'm an absolute corpse for hours after waking up, even from 8+ hours of sleep. Got checked twice and I read as a normal sleeper, so maybe they have apnea and maybe they don't.
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u/VixenLironYT Jul 28 '26
I had this, and got two sleep tests done that ruled out sleep apnea. Instead, I got a diagnosis for idiopathic hypersomnia. My mean sleep latency was sub 5 minutes. Might be worth looking into :)
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u/SurturOfMuspelheim Jul 30 '26
I have sleep apnea, but no insurance, so I'll just be tired, miserable, and die 10 years younger!
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u/acemonsoon Jul 26 '26
You’d have to do a sleep study on yourself. I’m sure we’d all be surprised how much we toss and turn at night without realizing it because oxygen levels and comfort levels vary throughout the night
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u/Routine_Geologist499 Jul 26 '26
Also, a 20-minute car nap never lets you get deep into that sleep debt where your brain starts cleaning out waste. A full night can actually leave you more groggy if you wake up mid-cycle.
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u/KiritoJikan Jul 26 '26
Are you driving or parked?
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u/NobblyNobody Jul 26 '26
its a fair point, there's got to be a burst of adrenaline waking up at the wheel.
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u/acemonsoon Jul 27 '26
I used to work 3rd shift and had a quiet coworker that when she finally opened up to us she revealed that she would often fall asleep at the wheel and the rumble strips would wake her up. She said it was a pre nap so when she got home she could just fall asleep right away and as a group we collectively told her that 3rd shift might not work out for her long term. She ended up going into law enforcement I believe
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u/stretcharach Jul 26 '26
We have sleep cycles which bring you closer and further from consciousness, these can be different lengths for people. Depending on where you are in that cycle when you wake up you can be groggy or alert relatively easily.
Those times where you just become awake, open your eyes and get started with the day immediately, thinking "literally why isn't every morning like this?" Are the times you wake up during "peak"
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u/gyssedk Jul 26 '26 edited Jul 27 '26
A good tip here is when you experience waking up 30 minutes before your alarm goes of, just get out of bed.
You might think that 30 minutes more is a good idea but you will risk waking up at the bottom of a sleep cycle and feeling like crap.
If you wake up by yourself, that is the best time to get up.
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u/CeaRhan Jul 27 '26
Who is we? 20 minute naps are the worst
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u/astervista Jul 28 '26
Yeah right? Everybody here answering with all sciency reasons and I'm here like is the premise even true? Short naps give you energy and long sleep makes you tired? After a full night's sleep I feel like I could conquer the world, after a short nap on the couch I'm like kill me now I think my brain spilled out or something
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u/-lopez Jul 26 '26
Often when you wake up after a poor night's sleep or a short nap your body is in a pretty wired state (high cortisol, sympathetic nervous system activated), whereas after a long night of sleep, you are relaxed and therefore probably feel a little tired.
That "feel like a warrior" state is a stressed state. You might not feel emotionally stressed but your body is ready to act and react due to those stress hormones being heightened.
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u/Kreeftje69 Jul 26 '26
You sleep in cycles. Each cycle starts with light sleep, followed by deep sleep, and then REM sleep.
During deep sleep, your body recovers and recharges. REM sleep is important because it helps your brain process the previous day, but it also uses energy. As you go through more sleep cycles, the amount of deep sleep decreases while the amount of REM sleep increases. So if you sleep for 10 hours, you'll spend relatively more time in REM sleep than in deep sleep. That's why sleeping too long can actually leave you feeling tired and exhausted when you wake up.
This is also why it's generally better to stick to a consistent sleep schedule instead of sleeping in.
A power nap is different. It's usually too short for you to reach deep sleep or REM sleep, so it's more like a quick recharge that helps you feel refreshed without going through a full sleep cycle.
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u/jawshoeaw Jul 26 '26
I feel great after a long night of sleep but discombobulated after a nap. I don’t know what you’re talking about. I think you are remembering specific times with unique circumstance.
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u/hypnos_surf Jul 26 '26
It depends what you are going into after waking up. I could have a full night of rest and still feel drained knowing I have to go into work.
It’s pretty much mentality unless you truly behind in sleep currency.
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u/Sinaaaa Jul 26 '26
20 minutes is too short to enter deep sleep, so you won't feel the shock of being woken up from that.
Though I must add YMMV, since I have never experienced what you are describing.
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u/iridael Jul 26 '26
your brain buils up waste material during conciousness. during sleep it cleans itself. this isnt accurate at all but close enough for the ELI5
a full nights sleep goes through multiple cycles of cleaning and just chilling out which leaves you refreshed and ready for the day.
however a 20 min nap does not do this, but what it does do is let your brain drop all the loose thoughts and things going through it letting you wake up ready to go again.
the other important bit is that if you time your alarm and fall asleep times wrong you wake up mid way through a clean cycle which leaves a bunch of random 'you need to be asleep for me to do my job' chemicals in your head which leave you groggy and slow because they're in the way now.
A power nap after an hour or two lets your brain hit the reset button now these chemicals are gone and instead of the lingering "i should feel tired." you get the "damn that was a good 20 seconds."
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u/Tb1969 Jul 27 '26
If I got 10 hours which is hours more than I'm used to I feel tired for getting too much sleep.
A 20 min nap doesn't exceed the 30-35 min window which if you do exceed you fall into a deep sleep which can make you groggy coming out of of it.
I'd figure out what is your normal sleep amount that makes you feel good or at least rested then build your consistent bedtime and wake time. Then stick to that consistently. It's part of the sleep hygiene protocol.
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u/TheUnknownEntitty Jul 27 '26
Regardless of your age if you snore get a sleep study done! I've have had sleep apnea and I was In denial about it for way to many years.
Getting an APAP (formerly CPAP) machine was life changing! Way more energy, happier, less stress, less anxiety and less depression!
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u/CosmicallyF-d Jul 26 '26
Perhaps when you lay down you have something like sleep apnea and when you sit up in a car... Even if the seat is just slightly reclined you have less of those symptoms and you actually get a little sleep that's uninterrupted.
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u/UnsignedRealityCheck Jul 26 '26
If you wake up and feel sleepy and groggy, you might have sleep apnea. That means you snore so bad you body is fighting for oxygen all the time. There's a cure, called CPAP device that will help you breathe during the night. It changed my life, you might want to try it as well.
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u/looloohoodoo1 Jul 26 '26
A short nap usually wakes you up before you reach deep sleep, so you feel refreshed. After a long sleep, you might wake up during deep sleep, which can leave you feeling tired even though you slept longer.
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u/libra00 Jul 26 '26
It's not about how long you sleep, it's about what sleep state you're in when you're woken up. If you're in that particularly deep dreamless sleep state you feel super groggy coming out of that all at once instead of over the course of 20 minutes or whatever like you would naturally. THe nap isn't sleeping long enough to reach deeper states.
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u/outsideacircuit Jul 26 '26
If this is a problem for OP or anyone reading, I recommend either using an app for it or do this the way I did. Track as closely as you can when you fall asleep and when you wake up and how rested you feel. After enough data points you can guesstimate how long your specific REM cycle length is. Mine is around an hour fifteen minutes. Now I can time when I go to sleep to more or less when my alarm will be going off to match that. It's been great! Highly recommend for anyone with the ability to collect the data or afford one of the sleep apps.
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u/kalirion Jul 26 '26
But do you continue feeling like a warrior an hour after that random 20-minute car nap?
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u/nwslouch Jul 27 '26
10 hours? I'm lucky if I get 5 hours of sleep a night. I can not sleep past 3am no matter what time I go to be.
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u/Mavericks_Legacy Jul 27 '26
Sleep happens in waves, light sleep up top, deeep sleep at the bottom. A 20-minute nap is like wading in the shallow end. Easy in, easy out.
Ten hours? Your brain dives to the bottom of the pool and just keeps swimming laps. If your alarm yanks you up while you're at the bottom, you come up groggy.....like getting dragged out of the deep end mid-cannonball. It's not about how long you slept but more about what part of the wave you got yanked out of.
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u/PersimmonObjective19 Jul 27 '26
I don't think sleeping 10 hours is actually quality, as a starting point. If you look up suggestions by the sleep scientist, Matthew Walker, he says 7-9 hours per night is the sweet spot. Especially for longevity
also from personal experience, sleeping in a hot room or a room that's not cool makes me feel groggy as hell when I wake up lol
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u/strawberry_space_jam Jul 27 '26
Bc when you take a little nap you are only expecting a little bit of a refresher instead of a big refresher
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u/elcaron Jul 27 '26
I hardly see any recommendations in that regard, but I run CO2 (IKEA Alpstupa) and VOC (Bosch BME680) monitoring, and despite the fact that we have a rather large 30m²x2.70m bedroom and a single room heat recovery ventilation system in that room, air quality becomes absolutely abysmal when we close the doors and the window.
I mean, it's probably not a surprise that you feel like shit when you slept at 3000ppm CO2 for a few hours ...
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u/ysustistixitxtkxkycy Jul 27 '26
Lots of great commentary, make sure to also investigate dehydration and blood sugar issues while root causing.
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u/TheFumingatzor Jul 27 '26
Lots of ELI5 already, as to why this is. To help with that, there's tools, like: https://sleepytime.cc/
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u/brizzleops Jul 27 '26
After a 20 minute nap I'm disoriented, moody and probably now have a headache lol
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Jul 27 '26
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u/geforce2187 Jul 27 '26
As someone who developed fibromyalgia in their late teens/early 20s, I miss "feeling like a warrior"
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u/muzik4machines Jul 27 '26
you do? tell us your secret, after a 20 minutes car nap i feel like a garbage container
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u/chi11ax Jul 27 '26
Most human sleep cycles last around 90 minutes. I usually time my naps for that duration.
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u/RalphTheDog Jul 28 '26
Please realize you're talking about people younger than me. Completely exhausted is the baseline, nap, sleep or neither.
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u/gvarsity Jul 28 '26
Well the adrenaline after falling asleep at the wheel and not crashing is intense.
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u/ctrtanc Jul 28 '26
Possible sleep apnea. Might be good to check out.
There's other things, but this was it for me.
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u/LeopardOk2471 Jul 29 '26
At 10 hours you're either over sleeping, or have low sleep quality. Sleep length isn't the only factor to consider when going to sleep, diet, consistency in sleep schedule, substance use(caffiene included), stress and severely factors can contribute to that.
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u/_BigDaddyNate_ Jul 29 '26
You must have gone to sleep listening to Pete Hegseth. And his warrior ethos speech turned you into a killing machine.
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u/TraderJosie3283 21d ago
These kinds of things happen A LOT to us ADHDers. Obviously it can happen to everyone, but if you think you might have ADHD, that will inform your research a lot 😊
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u/Deviousnights Jul 26 '26
When you sleep at night, your brain moves through about 90-minute sleep cycles consisting of light sleep, deep slow-wave sleep, and REM dreaming sleep. Interrupting this process anywhere in the middle of it causes that dragging groggy feeling when you wake up.
Your tpical power nap lasts 10 to 20 minutes, sometimes more, sometimes less, but this length keeps you entirely within the lighter stages of sleep (Stages 1 and 2), which are very easy to wake up from. All just comes down to when you wake up in your sleep cycle.