It's the difference between a broken bone and a charlie horse. If you try to walk off a broken tibia you can quickly cause serious permanent damage. If you try to walk off a cramping calf muscle you can infuse it with oxygen and return it to normal function.

Sarno's theory is that just like the brain can make the cheeks flush with embarrassment or go white with fear, via the autonomic nervous system it can constrict the capillaries and deprive various tissues of oxygen. He thinks this deprivation is minor and doesn't cause permanent damage, even though it can cause much pain. The solution, as for a charlie horse, is the opposite of immobilization, which is what I was doing. Mobilization heals via oxygenation.

He also believes that the ultimate source of the problem is the brain's reaction to sublimating emotions, that it deprives these tissues as a strategy to distract you from the sublimated feelings. That simply by raising this gambit to consciousness you can defeat it. I don't find this part of his theory as convincing, but I think the rest holds up without it.

There are lots of back problems that are more like a broken bone than a charlie horse, where mobilization is dangerous. I took the risk and got lucky. Even so it may have been a stupid move. It's a really good idea to get examined by a specialist first, which Sarno emphasizes.