Weekend marathons may work for your schedule, but they aren't the best approach for your dog -- at least not initially. Shorter runs and more of them will benefit your dog and your cardiovascular system. Just make sure to be consistent. Actually, your dog will help. When he's waiting by the door with his tail wagging, it'll provide added motivation and keep you from backsliding. Once you've both built up some stamina by increasing the length of your runs over a number of weeks, you can take more of those longer, weekend runs in stride -- no pun intended.