During the night, your sleep is punctuated by several cycles. The cycles themselves have phases: the sleep slow and sleep paradoxical. The sleep slow usually takes 60 to 75 minutes and the sleep paradoxical of 15 to 20 minutes. An average cycle therefore lasts about 90 minutes.
The sleep slow is itself divided into stages: falling asleep (between drowsiness and drowsiness), sleep lightweight, sleep deep during which brain activity slows down and sleep very deep. During the sleep very deep, brain, muscle and organism are at complete rest. It is often very difficult to wake a sleeper during this phase.
The sleep paradoxical is often more agitated. Breathing speeds up, eyes can flicker and brain activity is intense. Dreams come during this phase. During the first part of the night, the sleep paradoxical lasts longer inside cycles.
A cycle of sleep is preceded by a calm awakening and followed by an intermediate phase, during which the sleeper connects either on the following cycle or on the awakening. A person may even wake up briefly between cycles but she may not remember it.
The needs in sleep vary during life but an adult needs an average of 8 hours per night, which can be divided into 3 to 5 cycles. However, little sleepers are perfectly satisfied with 5 hours. The ideal is not to cut a cycle of sleep.
The quality of the sleep is essential for good shape but also good health. It removes muscle tension, the legs lose their heaviness, it triggers the secretion of growth hormone in children and of course allows to evacuate fatigue.