This machine works exactly the opposite from a traditional ab crunch machine. Rather than working your ab muscles from the top down, the Ab Coaster PS500 works from the bottom up, helping you target those hard-to-reach lower abs. Just kneel on the comfortable carriage, and pull your knees up. It’s as simple as that! As you lift, the knee carriage glides along the biometrically-designed curved track, engaging your lower abs first, then the middle and upper region, giving you a complete abdominal workout from the bottom-up. The PS500 is the base model for the Personal Series home market.