Ab Cycles

Setup
Lie on your back with legs straight and raised slightly off the ground, and hands behind your head. Roll shoulders off the ground by contracting abs.
Movement Instructions
Bend and bring one knee in and overtop of the chest, then extend the knee to return the leg to starting position. Repeat with other leg continuing to alternate throughout the exercise.
Comments
Keep a constant pace throughout the exercise, do not rush. Hands can be at either side of the head to support, but do not pull your head with your arms to help.