Ever woken up from a nap feeling even groggier and tired than you did before? What about that zombie-like feeling you get after a night of fitful sleep? Have you ever had someone claim you were asleep even though it felt like you were fully awake?

That’s because not all sleep is created equal. In fact, throughout the night (or in the afternoon if you take a long nap) you actually go through several distinct stages of sleep. And while you might not be conscious of the changes in your body as you cycle through the stages, you’ll definitely feel the results of being woken up mid-cycle.

Understanding how your sleep cycle works can help you get more restful, restorative sleep.

Sleep Cycle Stages

Your sleep cycle can be divided into 5 distinct sleep stages:

Stage One

You’re in a light sleep, hovering between being awake and falling asleep. Your breathing and heart rates become more regular.  It’s sometimes referred to as relaxed wakefulness.

Stage Two

Your body temperature drops and you become more disengaged from your surroundings.  Your eye movement also stops. This is your body’s way of preparing you for deep sleep.

Stage Three

Stage three (as well as stage four) includes your deepest and most restorative sleep. Your blood pressure drops, your muscles relax and your breathing slows.

Stage Four

Blood supply to your muscles increases and your body grows and repairs tissue, releasing hormones that are critical for recovery, growth and development.

Stage Five – REM (Rapid-Eye-Movement) Stage

A lot of the most important things happen during REM sleep.  Surprisingly, your brain is actually more active during REM sleep than when you’re awake.  It’s when you dream, and, when your brain processes and synthesizes memories and emotions from your day. Your eyes dart back and forth rapidly (hence the name) and the rest of your muscles are essentially paralyzed.  REM sleep stimulates the parts of the brain we use to learn.

 

 

REM vs. NREM Sleep

Our sleep includes phases of alternating non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep that repeat themselves about every 90 minutes. Non-REM sleep accounts for about 75% of your sleep cycle (stages 1-4), while REM sleep, the period where we experience intense dreams, only lasts for about 25% of your sleep cycle.

“REM sleep only accounts for 25% of your sleep cycle”

Waking Up In the Middle of a Sleep Cycle

That disoriented feeling you get after waking up from a nap? You probably woke up during stage three or later.  In order to get the benefits of nap without the grogginess, it’s recommended to either keep it to 15 to 20 minutes, or go the full 90 minutes until you’re back at stage one. Anything in between is a recipe for the blahs.

The same thing applies to sleeping at night. While we’ve all heard the adage that you need 8 hours of sleep each night, the reality is that it’s not just about the overall amount you sleep. It’s about the number of complete sleep cycles we go through over the course of the night.

It may seem counter-intuitive, but it’s possible to sleep for fewer hours yet waking up feeling more rested.  For example, waking up at the end of a sleep cycle after about six hours (4 full cycles) may make you feel more rested than waking up after 8 hours but in the middle of a REM cycle.

Now that you have a better idea of what your body is up to when you’re asleep, you can try to optimize your sleep schedule so that you are not waking up in the middle of a sleep cycle, allowing you to get a great night’s sleep and to wake refreshed.