My dd, who is 6, has started to tense her leg muscles while watching TV. She doesn't do it all of the time, maybe once a day. She'll slouch down and point her toes and tense her legs for a few seconds, stop and handflap, and then do it again. After just a couple of minues, she's hot, red, and clammy. You can interupt her by asking questions. You can tell your being a PITA to her when you do it, but still, I'm the mom. If you ask her what she's doing, she'll say "music box". That's from Chitty-Chitty Bang Bang - there's a scene where the female lead is dressed like a music box and stands on a toe and turns around and sings and dances like a robot. She can dance and sing like that lady, so I'm not sure why this exercise makes her say that, except that she has her toes pointed.

It reminds me of isometric exercises. I assume she's getting deep pressure input from it. Anyone else have this expericence or an opinion?

My 9yr old son has been tensing his whole body like that since he was little. I too thought it looked like isometrics and I still think it's sensory related. He does it when he's excited especially. At first I worried that it was some kind of siezure activity, but like your daughter he is still able to respond during the episode, so I really don't think that anymore. He pulls his arms in (like flapping) and stands on his toes and his whole body is tense. I think it may "look funny" to others, but I've really gotten past some of that in the last few years. He craves deep pressure and I just can't give him enough therapy to satisfy that so I let it go. I used to try to make him stop flapping and the body tensing by giving him prompts like "hands down" or "feet flat" to try to encourage a more "normal" appreance, but he always looked so sad when I prompted him. I finally decided that I can't control what other people think and as long as I didn't think there was some medical issue that was harmful I will just let him be himself. He may outgrow it, but I just want him to be happy. This may not help much, but I wanted you to know you're not the only one. Good Luck.