Okay, okay, that title is a little dramatic and I apologize. But I wanted to grab your attention. Understanding how a typical sleep cycle works will help you to understand your sleep in general. And yes, I'll address the paralysis later in this article.
Learning About Your Sleep Cycle.
If you want to learn about the inner workings of sleep, you cannot help but learn about the Sleep Cycle. In a given 8-hour night's sleep, you will average about 5 full sleep cycles, give or take a cycle.
There are 2 types of sleep within these 5 stages. They are REM and non-REM. (or Rapid Eye Movement and Non-Rapid Eye Movement). Non-REM is also sometimes shortened to NREM.
There are 3 or 4 (depending on who you ask) stages of Non-REM, and one of REM. While in Non-REM sleep you do not dream, your eyes are still, your limbs are not paralyzed, and you breathe deeply.
Stage 1 – Light Sleep or Pre-Sleep (5-15 min long)
The first stage of sleep is called Light Sleep. This is when you are just starting to drift off to sleep. Small sounds or movements may wake you easily. You may even jump or twitch in your sleep. If not interrupted, once you cross this threshold, it lasts 5-15 minutes until you enter the next level of sleep.
Stage 2 – Base Sleep or Regular Sleep (5-15 min long)
The next stage of sleep is Base Sleep. During this stage, your body temperature drops and your breathing slows. Also, your brainwaves slow down, in order to prepare your body for the restorative stages of sleep. (These are theta waves if you are curious). Like Stage 1, Stage 2 lasts about 5-15 minutes from beginning to end.
Stage 3 – Deep Sleep (5-15 min long)
Stage 3 is called Deep Sleep, and this is the first of the restorative levels of sleep. Your breathing slows even more and your muscles relax further. Your brainwaves slow down yet again. Delta waves (extremely slow brain waves) start to appear. Again, this stage lasts about 5-15 minutes in duration.
Stage 4 – Deep(er) Sleep. (5-15 min long)
Remember back when I said there are 3-4 Non-REM stages depending on who you ask. Well, it is this forth stage that has experts split. Some experts combine stages 3 and 4 and call it a single stage (taking a total 10-30 min to complete). Others (like yours truly) believe these are two distinct stages. Here's why:
Almost all brainwave activity at this point are delta waves. This is differentiated from Stage 3 because in the third stage, we only see some delta waves. By the time you get to Deeper Sleep, that's pretty much all there is. This stage is even more restorative than stage 3, and again, lasts 5-15 minutes.
Stage 5 – REM Sleep. (10-60 min, increasing with each cycle.)
The fifth and final stage of the sleep cycle is called REM Sleep. As we stated before, this stands for rapid eye movement. And yes, your eyes do really move... rapidly.
You can actually observe someone in REM sleep rather easily. Their eyes either dart back and forth, or roll back and forth underneath their eyelids. REM sleep is the most restorative stage in the sleep cycle. It is in REM sleep where your body does its most significant work.
There are a few things that make REM sleep different from the other stages. Most significant is that this is when we dream. All dreaming takes place in this stage of sleep. Because our brain activity is similar to when we are awake, the body takes a major safety precaution: it paralyzes you.
Yes, that's right, you become paralyzed every single night!
Worry not though, this is temporary, and not a "strong" paralysis. You regain control when you leave REM sleep. This, of course, is assuming everything goes right. There is sleepwalking, where you should be paralyzed and you aren't, and Sleep Paralysis (Syndrome) where it takes you a couple of minutes to be able to move or speak after waking (being paralyses when you shouldn't be). This can be very frightening if you don't know what is happening. Usually, though, these issues do not happen. If you do experience these things, see a sleep professional right away. If not, I wouldn't worry about it.
REM sleep typically starts about an hour or hour and a half after falling asleep, and recurs about every 90 minutes, getting longer and longer with each cycle. During the first cycle, REM sleep last about as long as the other stages 5-15 min. It increases in length with each cycle, and can last up to an hour in the later cycles (usually early morning; think 4:30, 5:00)
Your breathing also becomes very quick and shallow while in REM sleep. It is harder to wake someone out of REM sleep than the other stages as well. Once REM sleep concludes, the Sleep Cycle restarts.
ALSO: If you are woken up in Stage 3, 4, or REM, you will feel incredibly groggy.
So there you have it. The Sleep Cycle. For all you Scroll-to-the-Bottom-ers, here is a re-cap:
Stage 1 - Light Sleep (5-15 minutes) -falling asleep.
Stage 2 - Base Sleep (5-15 minutes) -asleep.
Stage 3 - Deep Sleep (5-15 minutes) -begins to restore you.
Stage 4 - Deeper Sleep (5-15 minutes) - continues to restore you.
Stage 5 - REM Sleep (10-60 min, increasing with each cycle) - most restorative. this is where you dream. you are also temporarily paralyzed.