Maybe I could mention one little thing without getting attacked?
Dogs don't grin. They pant. They only look like they are grinning because their mouths are open. This is not to say that they are not happy after they run. I believe they are. I think they feel great when they are exhausted. We can tell that dogs are happy from other types of body language as well.

The only reason I bring this up is so people can be aware that there can be times when your dog is not feeling well and may be panting because of it and you should not assume that your dog is smiling and overlook the signs of illness. I know it has nothing to do with this topic but I thought it was important for people to know and couldn't see opening a new thread about it.

That's all.

Jay
(real name witheld for personal reasons. If you want to know them, PM me)