Each cycle starts with light sleep, progresses for sleep deepest, comes back to light sleep and finishes in one sonho' '. From the works of Kleitman, it was transferred to identify two very distinct periods of training to it of sleep: the sleep of slow waves or NREM and paradoxical sleep REM or. These periods of training get excited during the night, forming cycles with approach duration of 90 minutes. To the end of a night, we complete the four six cycles of sleep, being that in the last cycles it increases the duration of paradoxical sleep (LOUZADA and MENNA-BARRETO, 2007, P. 58). As Becker (1993), each cliclo of hard sleep around 60 the 100 minutes, in way that evolves in four the six cycles.

Period of training NREM is divided in four periods of training and remembers the vigil, thus the individual can easily be despertvel, moreover, normally, is predominant in the first part of sleep. In accordance with Becker (1993, p.16), ' ' sleep NREM is to the times called sleep? calm. During sleep NREM, the breath it is slow and regular; the arterial pressure is low and has little movement muscular' '. Its periods of training are called 1, 2, 3 and 4: in period of training 1 it has the sleepiness, that it lasts, on average, five minutes, being still easily despertvel, in this phase the dreams directly are related the recent events. Period of training 2 it lasts about ten minutes and the individual already sleeps, but not deeply, in way that is not waked up with easiness and sleep already it can occur effectively. No longer period of training 3, that it is very similar to the 4, is necessary huge stimulatons to wake up the citizen, with duration of fifteen the twenty minutes. Whereas 4 and last period of training of hard sleep NREM, at least, forty minutes of very deep sleep.