[Disturbed motor behavior in sleep]

Although majority of skeletal muscles displays reduced tonic activity during sleep it is well known that the body during sleep is not motionless. Studies from the beginning of the past century established that the contractions of the muscle groups and the movements of the body are the consequence of the influence of the afferent stimuli from periphery generated by the sleeper in an endeavor to ensure a better position of the body and a better sleep quality. The number of body movements represent the individual trait of the sleeper. Aside from the contractions of the large muscle groups, sleep can generate short lasting contractions of the distal muscles (fingers, muscles of the face) that could be detected at the beginning of the sleep process or in REM sleep. Though all these movements could be seen in healthy individuals, their existence may be a part of the disease and involuntary movements seen during the process of sleep, and then they differ from normal ones in their frequency, timing and distribution of the affected muscle groups.