The inside story on why it sometimes feels like you’re falling as you fall asleep

Have you ever been jolted awake by the sensation of falling, just as you were drifting off to sleep? If so, you’re not weird; you’ve got plenty of company. These involuntary muscle twitches in the arms, legs, or entire body are called [sleep_term id="1194"](or sleep starts), and they’re very common. Up to 70 percent of people experience them occasionally—but no one knows exactly what causes them.

Naturally, there are some theories. One is that they’re a result of the natural downshifting of the nervous system that occurs as you’re falling asleep: As your breathing and heart rate slow down and your body temperature drops, your muscle tone shifts, and these twitches occur during this transition. Another theory suggests that as you’re drifting off to sleep, your brain misinterprets the relaxing of your muscles as a sign that you’re actually falling and signals your muscles to tense up, in order to protect you.

More often than not, hypnic jerks are nothing to worry about. If one wakes you up, simply roll over and go back to sleep. But keep in mind: a high caffeine intake, strenuous evening activities, emotional stress, or sleep deprivation may increase the frequency and intensity of hypnic jerks. If you suspect that one of these factors may be worsening your nighttime muscle twitches, try cutting back on caffeine, using relaxation techniques to help you decompress, or practicing better sleep hygiene. And if the jerks themselves—or your anxiety about having them—prevent you from getting enough sleep, talk to your doctor.