My daughter, 34, moved in with us two weeks ago. She is a cross country runner and jogs 6 miles a day. She asked if she could take one of the dogs with her, and I told her to take Merlot, the male chocolate, as he is the one with all the excess energy. She brought him back home after 10 minutes, said he wanted to stop at every tree and fire hydrate, and ruined her stride. So now she takes Zoey, the female yellow and she is no problem. The first day Zoey petered out after 4 miles and sat down. The second day she sat down after 5 miles, but now she is running the whole 6 miles and wants more. She is almost two years old, and other than drinking a ton of water when she gets home, she seems very happy and looks forward to the jogs. She starts going crazy and jumping on the door when my daughter puts her jogging shoes on. Is a six mile run safe for a two year old lab? :-\
I jog with my dog and that is normal. He stops alot. It takes some training. I give Rocky some pee time during the first 5-10mins cuz we go after he's been in the crate for many hours. Others train to NOT pee during the run at all (they may warm up with a walk and let them pee then).
Also - even if the dog has alot of energy DO NOT take them for 6miles right away, it is a different kind of exercise for them. Start for a few minutes than work your way up with time.
If you have read the other thread I don't have much to add other than to reiterate what Tanya said. I would NOT start a dog doing 6 miles. That is the perfect way for a dog to pull or strain a muscle. As with any new exercise they have to be conditioned into it.