Heat Stroke?

I took Mosey for a very vigorous run around the parking lot.  Well, he was running, I was rollerblading, and he was pulling me.  He was also chasing Jason on his bike.  I haven't been so scared for awhile!  When we got back inside, Mosey seemed especially tired and hot.  So soaked a towel in cold water and put it on his back.  

He didn't mind at all.  He didn't struggle with it or try to chew it to pieces.  He just laid there...  :]