Fitness has always been a little silly, when you think about it. In history, we would throw rocks as far as possible or hold a big stick and try to hit another guy off of a horse. Now it's glow-stick Zumba on surfboards with dogs. OK, not quite -- but we do continue to find new, fun, creative ways to move our bodies. At the IDEA World Fitness Convention this past weekend, we saw and tried the most inventive, coolest workouts around. Here are eight of our favorites.