Why do kettlebells produce results?  Because of the way you use them.  You don't "workout" or "train" with a kettlebell, you practice.  It's like practicing the piano - you try to improve your performance by refining your technique, learning when to work hard and when to relax - you don't just "go through the motions."  These concepts can and should be applied to all exercise but it's easy to be mindless when you're on a treadmill or exercise bicycle or swinging lightweight dumbells or pushing the lever on a machine.  The kettlebell affords the user no such luxury because it insists on having your full attention, one of the wonders of the kettlebell's design that features the center of gravity several inches away from the handle.  And because there is obviously no point in practicing when you have less than your full concentration, the kettlebell rewards you for stopping well short of muscle failure. It is a very 3-dimensional way to workout whether you are an avid fitness enthusiast or a beginner.