Whenever I hear the words "back pain" I ALWAYS suggest yoga.
If you don't know what yoga can do for you you just don't know. It's safe, effective, singularized, energizing, inexpensive, challenging, progressive and social.
Strengthening one's back while improving its flexibility works WONDERS!
Give it a try. Many studios offer beginners month packages.
We do yoga in a 105 degree room. It's generically called "Hot Yoga".
Our studio is styled after Bikram Yoga (named for Bikram C. a weightlifter who developed the regimen after injuring himself).
Try yoga at plain room temperature first. The hot room turns many people away.