Learn more at http://www.spine-health.com/wellness/exercise/low-impact-aerobic-exercise
Along with specific back exercises, aerobic exercise that increases the heart rate for a sustained period is very beneficial for helping back problems.
Aerobic exercise increases the flow of blood and nutrients to back structures which supports healing, and can decrease the stiffness in the back and joints that lead to back pain. While many patients with back pain are able to participate in vigorous exercise like running or step aerobics, others find it easier to engage in low-impact exercise, which does not jar the spine.