GHD Sit Up September 15, 2014ExercisesSSD Set up GHD machine so that butt hanging just off the edge of the pad. Secure your feet with a slight bend in your knees. Lay back as deep as you can go and sit all the way up until you can touch the piece that secures your feet. Initiate this movement by firing your legs. As you get more comfortable try to touch the ground behind you on the bottom and come all the way up to the top.