Some believe that the chaotic motion of the human in sleep are associated with insufficient blood circulation. In this case we say that the body during sleep numb. In an attempt to restore blood flow, the body forces the person to move. Often, poor circulation is inherited and can talk about some of the diseases. Such people experience weakness or a tingling sensation in the limbs in the morning.
Another cause of restless sleep is stress. If the day was too stressful, and you have failed in the evening to relax, then it is likely that muscle during sleep will shrink, trying to relieve tension, this kind of relaxation for the body.
Probably many have heard that there are several levels of sleep. Now, being one of them, a person does not perceive the world around him, he seemed disconnected from it. Simultaneously, the sleeping brain is able to respond to the needs of the body. For example, if in your organism there is a shortage of any vitamins, like calcium and potassium, in sleep the muscles will shrink, causing sleep to twitch.
Sometimes the twitching is because when a person falls asleep, he cannot fully fall asleep, something prevents him. In these moments, he startles, wakes up and then sinks back into slumber. These kind of transitions may be repeated several times until, until a restful sleep.
There is another, not the explanation that people twitch in their sleep. The fact that the dream is somewhat reminiscent of death: pressure and body temperature drop, even the breathing is slowed down considerably. They say that the human brain is not always able to perceive this state as sleep, it does not understand, relax you or die. For these reasons, the brain from time to time sends to the muscles nerve impulses, causing the body to shudder. Allegedly, due to this, the brain is able to make sure that the body is alive.