A third way to improve or maintain your lumbar mobility is the prone press-up. You perform this exercise by lying on your stomach. Start by placing your hands with palms down under your shoulders with your forearms in contact with the floor. Straighten your elbows slowly so that your chest presses up and your back extends, maintaining contact with your stomach and hips to the floor. Hold 30-45 seconds and then return back down to the floor. Repeat this a couple times.
If this is easy and you have no pain with this, you can progress this exercise by straightening the elbows all the way. Again, try to keep hips in contact with floor.
This is a good exercise to maintain spinal extension range of motion and keep you moving in a healthy way.