Running with a dog is SO awesome. I run regularly with my black lab/bird dog mix, and he's the perfect partner. Never complains about my pace (too slow!) and never seems to get tired. I haven't gone long distances with him yet, but dogs are built a bit differently than humans.
The best person to ask this of would be your vet; the answer is going to depend a lot on the breed and animal's history. The main thing is to build up JUST like people do. SP had a great blog on running with dogs (although it doesn't mention supplements.) www.sparkpeople.com/blog/blog.asp?post=10_
In general, I would assume the same tips you deal with for YOU would go for him. When you need a refueling break, give him one too. When you need water, give him some too. Watch his weight; sometimes when we exercise more frequently, I have to feed my dog more often because he'll start to lose weight more quickly and his ribs start to show. (He's a very lean mutt.)
If you haven't yet, it's probably time for a trip to the vet for a checkup to see how he's doing, and get any advice that the vet may have. :)
Edited by: DRAGONCHILDE at: 5/29/2013 (11:08)