This exercise works the abs and lower back and is the proper version of an ab roller.
Steps
Place a barbell on the floor at your feet. Bending at the waist, grip the barbell with a shoulder with overhand grip.
With a slow controlled motion, roll the bar out so that your back is straight. Keep your arms straight throughout the exercise. Roll back up raising your hips and butt as you return to the starting position.
Tips
Practice raising your hips and butt as high as you can with this exercise.