In my case the cycling helps my sacroiliac nerve problem, if I cycle less it tends to come back. However, i changed my bike and it returned for a while and I had to se the chiropractor again. I tried a few changes, but it went away agin before I could 'ring' the change that had caused it, which may of course have been something completely different that brought on the relapse. Interestingly the pain isn't always where the problem is, the pain defers - and in my case I often get the first signs in my neck and numb fingers, long before the pain in my lower back and legs. I also carry a slight knee problem and often find that when the knee starts to hurt, if I don't get it seen to, the back pain often follows.
Your body is a machine, one problem brings on another.
I don't really know where I am going with this response, but I think I am saying that your back problem may be a number of factors, not necessarily the bike or the hill. I also wouldn't make a joke about being over the hill!
Mike