A 4-minute ab workout? Thatís my kind of ab workout! :) Seriously, though, itís very good. You do 10 reps of 10 different exercises. Some are simple, like regular crunches, for example. Others are a lot more challenging, such as lying prone and pulling your legs in from flat on the ground, quickly. This one is not as hard as Ab Ripper X, but it still makes a great add-on for another workout. There is also a short stretch at the end, making the entire thing about 5-6 minutes.