There are several exercises in B&G that get my heartrate up- the leg presses, walking lunges, and the forward and side hammer punch lunges. Although it's not a cardio workout, IMO, it does have more of that feel than some of the other leg workouts. One reason may be the use of lighter weights.
Try the Leg Blast premix and I guarantee that you will get cardio benefits!! I sweat my butt off on this one.