I missed a spot when I wrote about back exercises. I only emphasized on the upper back muscles. The lumbar region is just as important, if not one of the most important ones. Many people have trouble spots from this region, owing to long sitting, wrong lifting of heavy loads, and other chores. A strong lower back promotes better posture and does wonders for the spine.
I found two exercises that would be good for the lower back. Unfortunately, no dumbbells this time. I think I have to inflate my Swiss ball again, to be able to do the first one.