Double fitness results from sit-ups and crunchesWonder Core works your abs twice as hard. Sit-ups and crunches only work your muscles on the way up; Wonder Core reclines, working your core all the way up and all the way down to double the resistance. With 180 degrees of motion, you can isolate and train you lower, middle and upper abs for a toner, tighter core. The recline stretches muscles, helping to relieve back pain. And you can also perform knees tucks and twisting oblique exercises on the swivel seat.