Have you noticed yourself or your partner twitching when asleep? Have either of you accidentally been hit by the other's sudden jerking limbs at night? Though research has been limited, scientists explain that these night spasms are perfectly normal. A large percentage of the population regularly experience themDr. William Kohler, medical director of the Florida Sleep Institute, believes that these sudden jolts, called hypnic jerks, are very much common with as many as 70% of the population experiencing them regularly. James K. Walsh, executive director and senior scientist at St. Luke's Sleep Medicine and Research Center, also maintains the belief that these occurrences are normal and explains that: It involves a total body experience where your muscle contracts therefore your limbs jerk or your body twitches. They generally occur during the transition between wakefulness and sleepA person's sleeping cycle consists of three stages before entering what is known as rapid eye movement, or REM sleep. Each stage lasts around 90 to 120 minutes with the cycle repeating itself throughout the night. These hypnic jerks usually happen between the moment you are beginning to fall asleep and the first stage of your sleep cycle. Sleep deprivation linked with twitching and vivid dreamingExperts believe that these sudden jerking movements occur mostly when you are sleep deprived similar to when you are trying to remain awake when you have something important to do. When sleep deprivation is higher, the body transitions from Stage 1 of your sleep cycle directly into REM at which point one is likelier to experience night spasms as well as vivid–sometimes even–lucid dreams to occur.This is due to the fact that when our bodies are forced to keep active when it is running low on sleep, certain parts of the nervous system are sleep while other parts of it remain awake. This unbalance is what triggers involuntary muscle contractions to occur when asleep.