Attach a pair of resistance bands to a door anchor. Place the door anchor on a door and adjust the height. Attach a handle to the other ends of the resistance bands. Sit forward on floor facing the door. Straighten lower back and slide hips back so knees remain just slightly bent.
Pull the handles to waist. Assist by pulling shoulders back and arching back to lift chest. Return until arms are fully extended, back is straight, and shoulders are stretched forward. Repeat.
Full range of motion through lower back will vary from person to person.