I have never had one with this, but it sounds like Malignant Hyperthermia which is a condition in the skeletal muscles. I know that greyhounds are prone to it.
I would speak with your vet about perhaps a consult with a board certified specialist so that you know how to manage it.
I am sure it must be frightening. I have a pup that does not know when to stop running and it is hot and humid here in the Houston area. I have to keep a close eye on her when we are in the back yard because she will just keep running until she is ready to collapse. I have had to put her in cool water quite a few times because she overheated and that can be fatal. Very scary.
Good luck with your baby! Sounds like she is going to be a pampered "air conditioner princess".
