When I was on the Pennine Cycleway my back caved in just as we were approaching Skipton and Dave's in-laws. My back was so bad that I cried off going to the pub with Dave, Dave and Ted. I stayed in and watched a program about Gram Parsons with Karen. She also has a bad back, and just as I was going for an early night she gave me some Arnica cream for my back.
http://www.internethealthlibrary.com/hom-library/arnica.htm
Seeing as how I have had my bad back for 24 years and have tried everything [twice] I had no hopes, to say the least, as I put the cream on my back. No heat, no relief ... I fell asleep.
Next morning my back was fixed - meaning that my spine was back in vertical alignment as the muscles had gone out of spasm - this was the first time ever that it had been remedied over night like that.
So, I now have several kilos of arnica just waiting for the next lot of field trials - I am cautiously optimistic, and very grateful to Karen.
The photo is of the cobbled high street in Heptonstall, which I cycled up before the back problem