This is an easy variation of the exercise that works the abs. It is a good option for beginners.
Lie down on a bench with your legs bent at the knees and lifted up a little.
Place your hands by your sides holding on to the bench.
As you exhale, slowly raise your legs so that your legs get parallel to the floor or a little higher.
Pause for 1-2 seconds at the top and, as you inhale, slowly return to the starting position.
Don't swing your body and don't jerk up your legs.
Don't put your legs down on the bench between the sets, keep them hanging.