The Sleep Cycle: Do You Get Enough Undisturbed Sleep?

by Angela (Oh She Glows) on October 7, 2009

Good morning!

1 day until US Shipping! The Online Shopping Cart will be activated Thursday at 9am EST. I will be providing a link from OSG and Glo Bakery websites at 9am sharp.

It’s funny because this week I have been swamped with Canadian orders!


I guess the Canadians want to beat the US rush! Smart thinking! ;)

Be sure to check out the Shopping Cart + Shipping FAQ for the answers to all of your pressing questions!

  • Please take special note of item 15 on the FAQ page. Keep in mind that quantities on the shopping cart will be limited to start off with. I am going to make available the amount of bars that I can make in a 2 week period. I want to ensure that I maintain excellent customer service which is why I have decided to control how many orders I will be getting all at once. Please don’t despair if you do not get an order in on Thursday! I will be updating the quantities on the shopping cart as I bake new batches.


How Do You Sleep?

Speaking of losing sleep, I thought it would be timely to do a post on The Sleep Cycle from my book The Owner’s Manual For The Brain.

First, here are a few fun facts about sleep:

  • The average person gets 7.5 hours sleep
  • Infants get on average 14 hours sleep
  • Seniors get on average 6 hours sleep
  • Before the invention of electric lights, humans slept for 9 hours on average
  • When all cues to time of day are removed (pitch black), humans sleep about 10.3 hours

How do you measure up to these stats?

Personally, when I don’t have my alarm set, I naturally wake up after 8-9 hours of sleep.

The Sleep Cycle is KEY!

  • However, it is not the length of sleep that we get that causes us to be refreshed. It is actually the amount of complete sleep-wake cycles that we get!

Each sleep cycle has 5 phases:


[Image source]


The average cycle is 1 hour and 30 minutes, however cycle length can vary from 60-120 mins. depending on the person.

If we truly were to sleep without any disturbances and no alarm clocks, we would always wake up on a multiple of 90 minutes. For example after: 4.5 hours, 6 hours, or 9 hours of sleep.

E.g., 5 complete sleep cycles = 90 mins + 90 mins. + 90 mins. + 90 mins + 90 mins = 7.5 hours of sleep.

Non-REM sleep lasts about 70 minutes per cycle, while REM sleep lasts about 20 minutes per cycle. REM sleep is when we DREAM!

Here is the kicker:

A person who only gets 4 cycles of undisturbed sleep (6 hours) will actually be much more rested than a person who has slept for 8-10 hours but who has not been allowed to complete any one cycle because of being awakened before it was completed.

This is why many top sleep doctors advise people not to sleep with pets in the bed, because often pets disturb your sleep several times during the night and you feel very tired the next day and not know why.

I wish Eric and I could follow this advice! ;) Sketchie happily sleeps at Eric’s feet every single night and we wouldn’t have it any other way.

Want to wake up easier? Don’t wake up in REM sleep!

The time between our REM sleep (stage 5) and Stage 2 is called the Twilight Zone (Stage 1). The Twilight Zone is the brief period in between each 90 min. sleep cycle. If you are in Stage 1 of sleep, it is very easy to wake up. You will find that any light stimulus will wake you from a light noise to the sun rising.

Waking up in the second half of your sleep cycle (especially during REM sleep) is often very difficult. Many people report not being able to wake up.

Get this: When we are in REM sleep, our motor output system from the brain is completely shut down (this is why we dream that we are running but we don’t actually run) and also explains why we feel so lifeless when we wake up during REM sleep! Now of course, the motor output system doesn’t always turn off, and we see this especially with sleepwalkers. That is another topic though!

This morning, I woke up in the middle of a dream (REM sleep) and I felt like I was hit by a truck when my alarm went off (even though I had technically the proper ‘length’ of sleep!). I couldn’t wake up for a good hour and walked around like a zombie.

However, if you wake up in the beginning stages of sleep (especially the Twilight Zone), you will find that you wake up easier and feel so refreshed when you get up. I often wonder why some mornings it is so easy to wake up and others it is a battle. This explains a lot!

So fun things to try out:

  1. Keep a Sleep Journal.

Record the beginning and waking times for each natural sleep episode that is uninterrupted by an alarm or other disturbance. Find the common multiple. For example, if your recorded sleep periods were 400, 500, 400, 200, and 700 minutes, you would conclude that your personal sleep cycle typically lasts 100 minutes, or 1.6 hours. If you don’t want to keep a journal, just assume it is 90 minutes in length.

2.    Plan your waking accordingly

For example, if my cycle is 90 minutes and I fall asleep at midnight every night, I should plan to wake at any of the following times: 6am, 7:30am, or 9am. All three of these times are multiples of 90 minutes. I would technically be waking up after a full sleep cycle, ideally. If I got up at 8:30am, I would be getting up in the later stages of sleep and would probably find it more difficult to wake up. Apparently there are devices that you can buy to simplify the process.

This morning, I naturally woke up in the Twilight Zone. I felt awake and ready to get up, but since it was earlier than I needed to get up I allowed myself to fall back to sleep for another 45 minutes. Well, when I woke up 45 minutes later it was almost impossible to wake up (I woke up in the middle of a dream). That’ll teach me! ;)

3.   Visualize Waking Up 

In an interesting study published in Sleep in 1997, participants were asked to visualize their time of waking on an imaginary clock face. Results found that those who visualized what time they had to get up were naturally able to wake up at the desired time without any alarm (this is SO me!). The key techniques: Get the same amount of sleep nightly, visualize the time you want to wake up, and use a back up (a clock set 10 minutes later than your desired time).


What are you sleep-wake patterns like? Do you think you get enough undisturbed sleep?


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{ 16 comments… read them below or add one }

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Paige @ Running Around Normal October 7, 2009 at 1:11 pm

How interesting! All of it’s interesting, but in particular, the whole waking up on a 90 minute cycle thing.

Can’t wait for US shipping! Although I kind of feel bad for you :( I hope you don’t get exhausted. Don’t do more than you can handle. I’m sure everyone will understand if they don’t get their orders in a snap to begin with :)


natalie October 7, 2009 at 1:16 pm

I get a pretty good night sleep. About 8 hours. I used to wake up in the middle and have to go to the bathroom but thankfully that stopped!! If we let our kitty sleep with us I’d get NO SLEEP! She is constantly purring and licking our hair and moving back and forth..we did it this weekend and it was a nightmare!! :) good luck with everything tomorrow. hope it goes smooth!!


K October 7, 2009 at 1:17 pm

Wow, that book seems like a real treasure trove of information! Lots of interesting information in this post.
My dad is totally one of those visualizing people. He just thinks about the time he wants to wake up and presto! No alarm clock.


leatitia October 7, 2009 at 1:19 pm

I love the bits about the motor system being down, totally makes sense now!


jeri October 7, 2009 at 2:08 pm

I’m very fascinated by sleep cycles etc. Based on times that I’ve monitored waking up and feeling rested vs. when I fell asleep, I had determined that I had a 45 min. REM cycle, but it looks like, based on this info., that would be possible. Maybe it is actually 90 minutes. I might have to do some more researching. sleep = research. Doesn’t get better. :)


Eve October 7, 2009 at 5:16 pm

Wow, thanks for posting this info – this is great timing for me, as I am literally just trying to figure out how much sleep I actually need – I’ve always though about 9 hours, but the last few days I’ve woke up fine after 6 hours, and had more energy than I usually do. Buuut, yesterday I fell asleep in the middle of the afternoon – and I NEVER nap, so I guess I haven’t quite figured it out yet! :)


Susan October 7, 2009 at 5:30 pm

This is SUCH an interesting post!! I’ve been struggling with sleep a lot lately. I used to be able to fall asleep at any hour and naturally wake up 9 hours later. But now I have to be really rigid about my bedtime or else I don’t get enough sleep. Now I feel refreshed after 7 hours… but maybe I should bump it up to 7.5! ;)


Tina October 7, 2009 at 8:19 pm

That was so interesting! My sleep is so interrupted unfortunately. I’m not even sure why. But those cycles make sense. On average I wake up 2 or 3 times at least through the night. I definitely never sleep all the way through the night. I think it’s so interesting how we would sleep so much longer in a pitch black room though.


Anne P October 7, 2009 at 9:21 pm

I find this stuff absolutely fascinating. Great post! That definitely makes sense why some days I wake up ready to rock, when others I’m like, kill me.


Kath October 7, 2009 at 9:29 pm

Great post Ange! So interesting.


Caroline October 8, 2009 at 11:30 am

Interesting! Maybe I’ll try getting up at 5:30 instead of 6 next week and see if its any easier.


Jess October 14, 2009 at 12:40 am

I’m just getting around to reading this post and can’t wait to experiment with it. I have been sleeping MUCH better this last week – I think it’s cause hubby isn’t around and I don’t have to listen to him snore! Plus, I’m usually the one who can sleep for 12 hours and STILL want more sleep.

Our cats sleep on our bed too and, while they do wake me every once in a while, usually they don’t bother me. I don’t think I’ll ever be able to kick them out – I just love waking up in the morning with them snuggled around me. :)


sleep walker September 15, 2015 at 10:21 am

Interesting read thank you! I want to clarify for you’re readers that sleep walking occurs during non rem sleep cycles 4-5.


sleep walker September 15, 2015 at 10:22 am



sleep walker September 15, 2015 at 10:25 am

My apologies! Auto correct on my phone….sleep walking occurs during stages 3-4 non rem sleep


dana September 6, 2016 at 6:28 am

don’t think I’ll ever be able to kick them out – I just love waking up in the morning with them snuggled around


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