I have been getting low intensity light therapy about two times a week for several weeks. This morning I woke up with a sore back and after thinking about yesterday's activities decided it was a short trip into the library with an unexpectedly heavy box of books I was donating that had triggered the discomfort. Had my light treatment a few hours ago. Back is now perfectly fine. I really don't know if light therapy is helping the PMR because, of course, pred is controlling that so well, but all my other back issues are being helped. I would have expected my back to take at least a day or two to recover.