Attach cable ankle straps to both ankles then attach ankle straps to cable. Lie supine on floor or mat, back far enough so cable is taut. Grasp support behind head.
Raise legs by flexing hips while flexing knees until hips are fully flexed. Raise hips from floor by flexing waist. Return until waist, hips and knees are extended downward. Repeat.
Movement can also be performed on bench. 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 Spot Reduction Myth and Lower Ab Myth. Also see Cable Lying Leg Raise.