I like to say that with great flexibility comes great responsibility. Nowhere is this more true than in the case of the bendy lower back. I know that those of you reading this who do not have naturally flexible lower backs are grumbling that you would be happy to have this problem, but time and again I have seen how the bendy lower back poses difficulties for aspiring flexperts. First, a little anatomy. The lumbar spine (the part of your back between your sacrum and the lowest attachment of the rib cage)