Plyometrics! Also another great workout. I'm not the biggest fan of following a DVD n working out (just not for me) but I must say insanity is pretty intense for cardio and working ur muscles. Just another idea for great endurance building cardio workouts. Especially if u don't have time to go to the gym n want something more than just goin on a run. Usually avg 45 min long sessions including warmup n 2 stretch periods.