My Kitten Oliver Chop loves to play. I throw his ball & he brings it back to me, he's very clever! However after he's ran backwards & forwards a few times he starts to pant with his tongue out. Obviously I always stop play at this point but I was wondering if this is normal behaviour or should I be worried. He's a very healthy little boy & has been fully checked over by the Vet. This only occurs when we're playing energetically. Oliver Chop will be 1 year old next month.