Once I had a dog. In fact the dog played a pretty big role in getting me out of the sofa and out on to the streets each and every morning. It was a border-collie, clever and playful. Poor dog had a very nervous nature and was afraid of all sorts of things. But it was also happy and clever and it was very easy to teach him all sorts of tricks. The dog was a he, therefore I refer to it as him.
Border-collies are sheep dogs that need to run every day. If they don't get their exercise they get bored and difficult to take care of. Some of them bite, but my dog never did anything like that. If he didn't get to run he was difficult and kept seeking attention all the time.
The best thing he knew was to run outside of town with me, where I could release his leash and let him run free. He could run very fast and far. I sometimes took him on a trip which took the whole day and he could go on and on forever. The only runs he wasn't allowed to accompany me in were races and when I ran with my running group. And I didn't want him with me when I ran along the highway 30 km or more.
It is illegal to let dogs run loose in town so he had to be on a leash near my home. But the town is not big and it was fairly easy for us to get out of town where he could run as much as he liked. I had to be careful that there were no sheep around because he didn't know how to behave around them. He was obviously a sheepdog, but never got the proper training for that. Instead he was an excellent runner's dog.
Usually I kept him by my left side, but that could be a problem when we met other runners. Then the dog would be between me and the other runner and that would make the dog stressed. But he had to learn.
I am sure that he was born leader of the pack, he always tried to be first and it wasn't easy to teach him to heel. If I said something like "good dog" or other nice things to him when he was at my side as he was supposed to be, he got all giddy and happy and ran faster because he was so happy, and ended up in front of me. Just what he wasn't supposed to do.