Attach a resistance band to a door anchor. Place the door anchor at the bottom of a door. Connect the other end of the band to a D-ring on an ankle strap. Lie supine on floor or mat with knees bent and feet placed on floor. Grab handles with overhand grip at the sides of your body.
Flex waist to raise upper torso while keeping lower back on floor or mat. Raise torso up as high as possible. Return until back of shoulders reconnect with floor or mat. Repeat.