The Ab Coaster is no joke. It's like performing a reverse curl against the force of gravity. Using your abs, you pull your knees, which are perched on a padded cushion that slides up a curved track, toward your chest. And even worse, you have to control the sliding coaster as you return to the starting position, forcing your abdominals to work as they lengthen — not an easy task.
The fun doesn't end there. Nope! The seat twists, moving your knees to the side to work the obliques. Gunnar had me do four fun-filled sets with the Ab Coaster: 12 reps straight on, 12 reps twisted to the left, 12 more twisted to the right, and for the grand finale alternating between going straight up and twisting to either side. I have no idea how many reps we did on the last one; I was lost in abdominal oblivion. The happy trainer asked with a friendly smirk, "Do you want to say something nasty about my mother now?" Ha! I couldn't even speak.