DD is 20 months.
She is CONSTANTLY doing whiat I can only describe as pushing. It's basically exactly like this mama describes in this thread, but DD is not verbal enough to explain why she does it. She braces herself against something like the couch, her booster seat, the coffee table, the floor (if nothing else is available), crosses her legs, and flexes her entire body. She strains so hard she flushes and sweats. I mean dripping sweat. She does it about 60% of the time that she's awake. She does it at dinner, before bed, in the bath, a story time in front of other kids, when she's sitting on my lap, when she's going to sleep. She takes a break from playing to push against the floor: Hands on the floor behind her, arms stiff, neck clenched in, legs crossed out straight in front of her, torso arched forward. She holds it until the muscles give and then does it again. If I ask her to stop, she can stop for a second, but then she's right back at it. It's like a complusion, but she does seem to be able to stop, so it's not like a seizure.
When we go out to eat, she pushes on the highchair through the entire meal. It's pretty dramatic. Once a family asked to be moved to a different table away from us. Everyone says, "she just doesn't want to be in the highchair" but she gets really mad if we try to interrupt the pushing. She was pushing on a booster at my best friend's house while we were eating dinner, and my best friend's husband told me that it made him uncomfortable. As a result, she can't sit in a chair without being strapped in, because she will push herself out and be upset.
In the other thread (from 2004), the posters tossed around the idea that it might be mastubatory, but she seems to be in distress when she does it. Grimacing, often near tears or actually crying, and she's done this since she was about 3 weeks old.
The only times she doesn't do it at all are when she's scared, completely asleep, or when she was nursing.
Has anyone known a child with this issue? Was s/he neurotypical?
Any thoughts are appreciated.