Lie back on incline board. Grasp handles and place forearms on arm pads to each side.
Raise legs by flexing hips and knees until hips are flexed. Return until hips and knees are extended. Repeat.
Rectus Abdominis and Obliques only contract dynamically if actual waist flexion occurs. With no waist flexion, Rectus Abdominis and External Oblique will only act to stabilize pelvis and waist during hip flexion. It may be necessary to completely flex hips before waist flexion is possible; see Weighted Incline Leg-Hip Raise. Exercise can also be performed on incline board. Also see Spot Reduction Myth and Lower Ab Myth.
Lower incline or lie on floor or bench to decrease intensity.
Elevate incline or straighten knees more to increase resistance. Once highest incline has been achieved, exercise can be performed vertically. Exercise can also be performed with added weight.