Elliptical trainers allow for an intense workout without the jarring and impact you get running. They offer the smoothness of the bike, but with the benefits of weight bearing and involvement of the arms (and without the sore bottom). Nothing else can elevate your heart rate so well with so little discomfort and so little punishment to your body. Even if you are experienced with other cardio methods, you may be shocked when you see how well your heart rate gets elevated on an elliptical with what seems like so little effort.