What are some good exercises to help relief back-pain if you have ankylosing spondylitis?

Extension exercises: Consider exercises that extend your spine. Consult a physician and a pt.

Flexibility-Core: You want to do a complete and diverse program beginning with flexibility and postural ones to avoid becoming "fused" in a bent over position leading to increased muscular pain in that case. Cardiovascular and core strengthening will help in general while producing your own pain relievers called endorphins.