Quote Originally Posted by Zen View Post
Core, as in transverse abdominus or showy abs as in rectus abdominus or obliques?
Curious, before I take time to research that DVD.
Both. The exercises work the transverse abdominus, rectus abdominus, external and internal obliques, lower back, and hip flexors (thus my use of the word "core.").

The set comes with a Yoga dvd, and a Core Synergistics dvd as well, which hit the core muscles in different ways than in the Ab Ripper X.