Stiffness in the lower back is often caused by weakness of the surrounding muscles. Bending backwards is not a motion that many of us train during the day, and the stability ball is the best tool to use for training this region.
The ball will get you off the floor in many traditional trunk extension motions and allow for greater resisted range of motion. As you perform many traditional exercises such as rows, pulldowns, and back bends, enjoy the added challenge of having to balance on the ball and hold it still. Many trunk stabilizers will be challenged throughout, training many muscles in every exercise.
Purchase the equipment used in this video from Amazon:
Neoprene Coated Dumbbells: https://amzn.to/39fNcQM
55cm Stability Ball: https://amzn.to/2OwYHZ5
65cm Stability Ball: https://amzn.to/2TZIgaw
Yoga Mat: https://amzn.to/2ZDSMrH