Dog is acting abnormally

Question
I have a dog (Bluetick Hound/ Australian cattle dog) that is about 9 mos. old. I took him to the local dog park yesterday(11-13-15)and played hard for about 2-3 hrs. I noticed when we were leaving, he did not want to jump into the vehicle. I had to pick him up. I thought that it might be he was just tired. Once we arrived home, I tried to help him out. when I touched his rear legs he kind of wimpered, so I let him get out on his own. Not thinking much of it I gave him a bath and all seemed fine. As the night grew later, I noticed he was groaning and seemed he could not get comfortable no matter where he layed. We went to bed i woke up this morning with him (Pepper) walking with his back arched up and walking funny on his rear legs. He is not eating or drinking much either. I have not noticed any cuts, swelling, or any abnormalities with his legs. Is he possibly just sore from all of the running around and playing with the other dogs or is there something more serious? Please help!Thanks.

Answer
This sounds a bit more serious that overexercise.  I would highly recommend getting him to the vet for an examination, blood tests and possible x-rays.  He could have a condition called rhabdomyolisis (tying up) or partially herniated a disc in his back.   He will definitely need some anti-inflammatories and muscle relaxants.   And I would encourage you to limit his exercise to smaller periods of time for the future and make sure that he is drinking some electrolytes during exercise.