re: shaky mare

["guest@endurance.net" <guest@endurance.net>]

Nikki Reynolds jakar@phonewave.net
I was hoping by now that someone would come up with the name of this condition and an explanation.  My gelding and I had done a ride in early fall after a rainstorm in CA and when we got to the vet check at lunch, my horse was shivering and most of the others weren't.  Now, I DO have a problem with him getting cold very easily, even while just out in pasture.  I was unsure at the ride whether or not he was just cold or whether I'd let him go too fast.  The vet had a $16 name for the condition... muscular somethingorother.  I've forgotten the term he used. 

Anyway, I told him I thought Jakar was simply cold because he'd been standing in the shade in the vetline (no choice) and our weather at home was still in the high 90's, whereas at this ride, it was much colder and breezy.  The vet said to blanket him and if the shivering stopped right away,(which it did) then he was just cold.  If the quivering continued or was confined to just a part of his body, then it was this other thing.  Now I'm curious about what this is, the metabolic cause, prevention, etc.  I've seen other horses with only their butt muscles or shoulder muscles quivering and I'm assuming this is what that vet was referring to.  Vets... can you help us out here please?  I'd like to know so I can tell the difference and whether my horse does have a problem with this. 
Nikki