One reason back pain is tricky is that the intravertebral muscles spasm to protect the spinal core, and the spasms don't stop for up to ten days. By that time, the patient may have seen three doctors and had three different therapies. When the spasms subside, they associate the last treatment as the one that "healed" their back, when in fact, 80% of all back pain resolves itself with or without treatment.
There is a growing body of evidence-based research into exercise and back pain. The most studied device is the MedX lumbar extension machine, invented by Arthur Jones, the genius behind Nautilus exercise machines. Slowly the knowledge to strengthen the specific perispinal muscles is spreading.