Have you ever felt heavy when you sleeping and your mind seems to be active and you know what you doing and when you try to open your eyes it seem like helpless
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In Chinese culture, sleep paralysis is known as "鬼壓身" (simplified: 鬼压身) (pinyin: guǐ yā shēn) or "鬼壓床" (simplified: 鬼压床) (pinyin: guǐ yā chuáng), which literally translate into "body pressured by a ghost" or "bed pressured by a ghost."
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http://en.wikipedia.org/wiki/Sleep_paralysis
Actually its called Hypnagogic Hallucinations - Sleep Paralysis is the symptom of it
Hypnagogic sensations are vivid dream-like experiences that occur as one is falling asleep or waking up. Accompanying sleep paralysis can cause the sensations to be more frightening. The features of these sensations generally vary by individual, but some are more common to the experience than others:
Most common: Vividness, Fear
Common: Sensing a "presence" (often malevolent); Pressure/weight on body (especially the chest); A sensation of not being able to breathe; Impending sense of doom/death
Fairly Common: Auditory sensations (often footsteps or indistinct voices, or pulsing noises). Auditory sensations which are described as noise instead of sensations of legible sounds, are often described to be similar to auditory sensations caused by Nitrous Oxide by persons who have experienced both. Visual sensations such as lights, people or shadows walking around the room
Less Common: Floating sensations (sometimes associated with out-of-body experiences); Seamless transition into fully immersive lucid dreaming, also associated with out-of-body experiences; Tactile sensations (such as a hand touching or grabbing)
Rare: Falling sensation; Vibration; Involuntary movements (sometimes the feeling of sliding off of the bed or even up walls); The feeling of being pulled in different directions
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so far i've encountered this prob 3 times in my life, tried to shout wen my mind was still active, body cnt move, oni eye ... den feel like somebody is there beside u, i tot its like some1 is alr wan to take my soul or somethin.. rly freakish i say... got cold sweat after waking up