Legs shake a little while sleeping, generally considered a normal physiological phenomenon, medically known as the release of the spinal cord phenomenon, may also be caused by periodic limb movement disorders or strain: 1, the release of the spinal cord phenomenon: the motor nervous system is divided into two levels, the cerebral vertebral cells of the cerebral cortex for the upper motor neurons, the anterior horn motor cells of the spinal cord for the lower motor neurons. Under normal circumstances, the cerebral cortex has a restraining effect on the anterior horn motor neurons of the spinal cord, but when the cerebral cortex is at rest during sleep, the role of restraining consciousness of the anterior horn motor neurons of the spinal cord is weakened, there will be spontaneous excitation of electrical activity, manifested as a sudden shaking of the legs, this situation is a physiological phenomenon, does not belong to the disease; 2, periodic limb movement disorders: between organic brain disease or Neurological degenerative diseases appear before the antecedent symptoms, manifested as toe or ankle episodes of dorsiflexion and accompanied by brief, rapid twitching, every few seconds or minutes and twitching, four or five times a night such phenomena, continue to occur frequently, known as periodic limb movement disorder, commonly in Parkinson’s disease, epilepsy, cortical basal ganglia degeneration and other diseases may appear before the onset, if it does not affect life, without 3, strain: such as long periods of standing, walking during the day, the lower limb muscle strain appears when sleeping leg shaking a situation, pay attention to rest, avoid overexertion; 4, other causes: if the body lack of calcium, or sleep at night when the lower limbs are cold, can also appear when sleeping leg shaking a situation, you can go to the hospital for examination, to clarify the cause of targeted treatment.