The sleep cycle is a set of phases, which begin from the moment the person falls asleep, progressing and becoming deeper and deeper until the body enters REM sleep.
Normally, REM sleep is the most difficult to achieve, but it is in this phase that the body really manages to relax and in which the rate of brain renewal is highest. Most people follow the following pattern of sleep phases:
- Phase 1 mild sleep;
- Mild phase 2 sleep;
- Phase 3 deep sleep;
- Mild phase 2 sleep;
- Phase 1 mild sleep;
- REM sleep.
After being in the REM phase, the body normally returns to phase 1 and repeats all phases until it returns to the REM phase again. This cycle repeats throughout the night, but REM sleep time increases at each cycle.
How long the sleep cycle lasts
The body goes through several sleep cycles during one night. The first lasts around 90 minutes and then the time increases to an average of 100 minutes per cycle.
An adult generally has 4 to 5 sleep cycles per night, making 8 hours of sleep necessary.
The 4 phases of sleep
Then, the dream can be divided into 4 phases that are interspersed:
1. Mild sleep (Phase 1)
This is a fairly light sleep phase lasting approximately 10 minutes. Phase 1 sleep begins the moment the eyes are closed and the body begins to fall asleep, however it is still possible to easily wake up to any sound heard in the room, for example.
Some features of this phase include:
- Do not feel that you are already sleeping;
- Breathing becomes slower;
- You may have the feeling that you are falling.
During this phase, the muscles are not yet relaxed, which is why the person still moves in bed and may even open his eyes while trying to fall asleep.
2. Mild sleep (Phase 2)
Phase 2 is the phase that almost all people refer to when they say they are light sleepers. It is a phase in which the body is already relaxed and asleep, but the mind is attentive, which is why the person still manages to wake up easily due to someone moving inside the room or a noise in the house.
This phase lasts around 20 minutes and, in many people, it is the phase in which the body spends the most time throughout all sleep cycles.
3. Deep sleep (Phase 3)
This is the phase of deep sleep in which the muscles relax completely and the body becomes less sensitive to external stimuli, such as movement or noise. In this phase, the mind is disconnected, which is why there are no dreams either. However, this phase is very important for body repair, as the body tries to recover from small injuries that arose during the day.
4. REM sleep (Phase 4)
REM sleep is the last phase of the sleep cycle, which lasts about 10 minutes and usually begins 90 minutes after falling asleep. In this phase, the eyes move quickly, the heart rate increases and dreams appear.
It is also in this phase that a sleep disorder known as sleepwalking may arise, in which the person can get up and walk around the house without waking up. The REM phase becomes more extensive with each sleep cycle, and can last up to 20 or 30 minutes.Â
see also How to sleep fast: 8 techniques that can help you
