Lie on your back. Rest your hands by your sides, palms facing down, or place your hands underneath your butt for a little leverage.
Extend both legs out so they are a few inches above the ground. Draw your lower abs in, pressing your lower back into the floor.
In one fluid motion, bend your knees into your chest, press your hips up as high as you can, lower your hips to the floor, and extend your legs straight out.