I run with mine all the time! She's naturaly a good walking partner and has adapted well to the increaded speed. We use a flexi, which gives us each some room to let our bodles move naturally. I look at her frequently to see if she needs to slow down for a pee or a sniff (it's certainly not a race) and we do fine. If the dog has never had basic obedience, it's a good idea. Other than that, go for it! Again, don't expect to set a speed record, but you both will have fun. A tired dog is a well behaved dog!
Be yourself, to the extreme!