I have an English Bulldog and I enjoy watching him do his dog stuff. After getting more interested in ancestral (aka primal, paleo, etc.) health, I started to watch him for more than enjoyment. I noticed some lessons I can learn from him regarding exercise.
First, bulldogs are solid muscle. They are not naturally fat. A fat bulldog is a sign of an over-indulgent owner, and that's bad for the dog. But I digress. Bulldogs of all types are solid muscle, naturally. But they don't lift weights or do cardio on machines. They just do dog stuff. Oh, by the way, bulldogs do need a fair bit of exercise. The laziness is a myth. No, they aren't crazy runners like labs or border collies, but they do need a couple miles of walkies every day.
Now, if you take a dog to a big field, or you live on an acreage, you can leave them off the leash and observe their instinctual behavior. My dog likes to patrol. He walks the perimeter rather slowly. Every now and then, he sprints like crazy. Way faster than I can. Apparently bulldogs are natural sprinters. Now, given their weight, bulldogs really only need that walking/sprinting to maintain muscle tone. But they also like to play. He's big on tug-of-war and chewing, both of which are great for his neck and jaw muscles. So all of their activity is 'working out' in a way, because it's exercise, but ultimately it's just play.
So the first lesson I learned: make exercise more like play. Second lesson: walk a lot, but slowly. Spring occasionally. The third lesson comes from watching him jump his weighty butt onto a couch. And that is to lift heavy things occasionally. It's all about functional fitness, because he wasn't doing anything to look good. He's already pretty :).