As one who must train her body to slow down the monster called Degenerative Spine Disease, I must work out consistently. I also must train intelligently. Moving your body properly, in correct posture, with control of motion is important when training with any type of work out. The link above has 5 exercises that you can do to improve the strength of your back in a low-impact way. Be sure to breathe (exhale during contraction and inhale during release), control your body, use good form. I would love to hear if you tried these Pilates-inspired exercises and if they are also helping you with maintaining a strong, healthy spine.
Move what you can, when you can,