During sleep, our body and brain go through several stages, from falling asleep to waking up. Sleep is not a straight path; instead, it is divided into different cycles. Over the course of a night, we typically experience 4 to 6 consecutive cycles, each composed of four main stages: falling asleep, light sleep, deep sleep, and REM sleep.<\/p>
On average, a sleep cycle lasts about 90 minutes and follows this order: falling asleep, light sleep, deep sleep, light sleep (again), and REM sleep. However, cycles evolve throughout the night. The first half is rich in deep sleep, while the second half consists mainly of light and REM sleep.<\/p>
This is the first phase, also known as stage 1. Since it leads to sleep, it is crucial that it occurs in the best conditions possible. During this stage, we may feel semi-conscious as our thoughts wander. Breathing and heart rate slow down, muscles relax, and the eyes move beneath the eyelids. As this is a very light sleep state, we can be easily awakened and may experience a sensation of falling or jerking awake.<\/p>
After just a few minutes, we typically enter the second stage of the cycle. This phase gradually lengthens throughout the night and makes up about 50% of total sleep. Although drowsiness deepens, we can still wake up relatively easily. Muscle tone remains, allowing movement such as turning over, but there are no longer any eye movements.<\/p>