Why do some people jerk in their sleep?
A hypnic jerk, or hypnagogic massive jerk, usually occurs just as we are falling asleep. People often describe it as a falling sensation or an electric shock, and it is a completely normal experience. It most commonly occurs when sleeping uncomfortably or over-tired. When we drift of into sleep, the body undergoes changes in temperature, breathing and muscle relaxation. The hypnic jerk may be a result of the muscles relaxing. The brain misinterprets this as a sign of falling and signals our limbs to wake up; hence the jerking legs or arms. In most people, a hypnic jerk usually occurs just once or twice a night. However, when a person is deprived of sleep or trying to fight sleep, it may happen more often. In extreme cases, the muscle twitches can happen every thirty seconds or more. This disorder is called periodic limb movement. Another theory put forward to try and explain the hypnic jerk is that the body reacts to falling asleep much in the way that a body may twitch when dying. The