Step by step instructions
Lie faceup with elbows bent 90-degrees by sides, feet flexed, and heels on top of step (bring hips close enough to step that knees line up over hips). Extend left leg as straight as possible to ceiling.
Tighten abs and press elbows down into the floor to lift hips, driving left heel up towards ceiling. Lower hips to floor, only lightly tapping the ground before lifting back up. Complete all reps on the first side, then switch legs and repeat to complete the set.