There is an adjunct movement to GHD sit-ups in which the athlete is dynamic in the trunk and static in the hip. It is the AbMat sit-up, where we deliberately take the hip flexors out of the equation and work the torso dynamically. The two sit-ups, GHD and AbMat, complement each other beautifully. One is dynamic in the hips and static in the trunk; the other is dynamic in the trunk and static in the hip. In conjunction with the L-sit (static in the trunk and hip), they develop a formidable capacity in the midline.