Thank-you to those who have posted the medical info (about endorphins, and the vagal system -- never even heard about the vagal system!). Knowing the 'technical details' makes it more calming for me when I make vigorous movements, because I can say to myself, "This is not a sign of madness; what you're doing is good for you. Keep going, keep those endorphins flowing."
My neurochemistry is unusually disturbed at the moment (my psychiatrist thinks it was triggered by relationship problems, and the pressure of having tried to live a 'normal' life for so many years). I was flapping and shaking and wiggling in the car all the way to work as I was driving (e.g. at a traffic light with both hands, and then when driving just with one hand or otherwise rocking as I was driving). I realised that other drivers could see me and possibly may have thought, "This woman is crazy or on some drug, and could have an accident!" but in reality the fact that I was doing it was calming and therefore I was actually less likely to have an accident because I was doing it.
I also decided, drat this 'suppression of stimming to please society' -- if I go to meetings or social events, I will 'behave' so as not to embarass my friends, and so that I can do business deals smoothly; but when I am driving, I am not anyone's colleague, companion or family member, so I can do what I want in my own car, and if I want to stim because it does me good, I will jolly well do it.
These days I also start my day by wiggling about or stretching and curling in my bed. When I was a child I used to do this before falling asleep.
At work I am usually bouncing my leg.
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When I must wait in a queue, I dance. Classified as an aspie with ADHD on 31 March 2009 at the age of 43.