A single sleep cycle for an adult human lasts an average of 90 minutes.
Each cycle is made up of four different sleep phases.
These phases repeat until the point when we wake up.
Each of the stages of sleep is characterised by certain features.
The deep sleep and REM sleep phases are especially important for our rest and recovery. 🔁
Phase 1 non-REM sleep: Falling asleep
The falling asleep phase begins from the moment we turn off the light and close our eyes. 🥱
This is where our heart rate, breathing and brain activity slows down.
This phase is unique as it is (usually) only part of our first sleep cycle.
In subsequent cycles, the body skips this phase and goes directly into a light sleep. 😴
Phase 2 non-REM sleep: Light sleep
While our eyes are still moving during the falling asleep phase, they come to rest completely during light sleep.
At the same time, our muscles slowly relax and we slide step-by-step into a deeper sleep. 💤
On average, we spend about half of the night in a light sleep phase.
Phase 3 non-REM sleep: Deep sleep
Finally, we reach the deep sleep phase, where our body can best recover. 💆
In this phase, our body activity is at its absolute minimum.
We are never more relaxed than during this phase. 🛌
The deep sleep phase is when our muscles, brain and immune system are able to recover.
We usually spend 30 minutes per sleep cycle in the deep sleep phase.
REM sleep (Rapid Eye Movement)
Suddenly, everything changes.
From one second to the next, our eyes begin to flicker and our brain activity increases. 🧠
This is because we have reached the famous REM phase.
This occurs between the end of one sleep cycle and the beginning of a new one.
The REM phase is where we dream.
Images, conversations, feelings and memories are awakened and classified in this phase. 🔎
After about 10 minutes in the REM phase, we either wake up briefly or return to light sleep.
The end of a REM sleep phase is widely considered the best time to get up. ⏰