Many people experience the sudden sensation of falling from a height while drifting into deep sleep [1].
This phenomenon, known as a hypnic jerk, affects a wide range of individuals and often results in an abrupt awakening. Understanding these involuntary movements helps clarify the relationship between the brain and muscle activity during the transition from wakefulness to sleep.
A hypnic jerk is characterized by a sudden muscle contraction that occurs as the body relaxes [1]. This physical reaction often coincides with a vivid sensory experience, such as the feeling of dropping, which causes the person to startle awake [1]. While the experience can be jarring, it is a common occurrence for most people [1].
Researchers said that the exact cause of these jerks is not fully understood [1]. However, evidence suggests the sensation is likely related to a misinterpretation of signals within the brain [1]. As the heart rate slows and muscles relax during the onset of sleep, the brain may occasionally misread these signals as a sign of danger or a loss of balance.
In response to this perceived fall, the brain triggers a rapid muscle contraction to correct the body's position [1]. This creates the physical "jerk" that interrupts the sleep cycle. Because the brain processes this information rapidly, the sensation of falling often feels instantaneous and realistic [1].
BBC Bengali said that most people have had the experience of waking up startled after feeling as though they were falling from a height during a hypnic jerk or deep sleep [1].
“The sensation of falling while asleep is a common experience known as hypnic jerks.”
Hypnic jerks represent a momentary lapse in the coordination between the brain's sleep-induction mechanisms and the motor system. While generally harmless, these events highlight how the brain maintains a level of vigilance even as the body enters a state of paralysis and relaxation during deep sleep.
