There's a great saying to keep in mind when you think about dogs and exercise. It goes, “A tired dog is a happy dog.” Why? Because when your puppy or dog is sleeping soundly at your side (or in her crate or bed), she's not getting into any trouble. Dogs who pace, whine, cry, dash around the house, get up and down frequently, bark for no reason, or constantly run to the door to be let out are not happy dogs. While some of that restlessness may be the result of their breeding or a lack of effective training, another part is a lack of sufficient exercise.