Sit in the ab machine with your back resting against the back support and your chest resting against the padded lever.
Hook your feet under the foot pads.
Grasp the handles for support.
Keeping your hips fixed, exhale as you push the padded lever down with your chest by flexing your waist.
Hold for a count of two.
Inhale as you return the padded lever to the starting position in a controlled manner by extending your waist.
Relax your waist before repeating from Step 1.
Comments and tips
Relaxing your waist before each crunch ensures that the muscles fully and dynamically contract for each repetition.
Seated ab machines come in various forms. Some of them have a padded lever in front of the body, as in the above example. Others are more like chairs. You sit on them, grasp the handles over your shoulders, and crunch by flexing your waist and pulling the handles down. Still other ab machines allow you to crunch your waist and flex your hips at the same time (see the machine leg raise crunch). Whatever the design of the ab machine, make sure that you adjust the seat and foot pads for optimal support, leverage, comfort, safety, and range of motion.