Sit on incline board. Place weight between ankles or use no weight. Lie supine on incline board with torso elevated. Grasp feet hooks or sides of board by head for support.
Raise legs by flexing hips while flexing knees until hips are fully flexed. Continue to raise knees toward shoulders by flexing waist, raising hips from board. Return until waist, hips and knees are extended. Repeat.
Exercise can be performed without added weight until more resistance is needed. Elevate incline to increase resistance. When raising hips, keep knees fully flexed, so as not to throw weight of lower legs over head.
Rectus Abdominis and Obliques dynamically contract only if actual waist flexion occurs. With no waist flexion, Rectus Abdominis and External Oblique will only isometrically contract to stabilize pelvis and waist during hip flexion. It may be necessary to completely flex hips before waist flexion is possible. See Spot Reduction Myth and Lower Ab Myth. Also see Weighted Incline Leg Raise.