Cardio is any activity that raises your resting heart rate. These types of exercise are mostly intended to burn calories & fat, and strengthen your heart. Cardio uses large muscles, typically the legs, in a rhythmic fashion. Some examples include, but are not limited to, running, bicycling, swimming, cross-country skiing, and of course my all-time favorite, cardio kickboxing. As with anything, though, always consult your doctor before beginning a new exercise regimen.