I've injured a muscle in my back, laying concrete, mostly pushing wheelbow full of concrete - by rough reckoning I shifted 12tons of it in 1.5hours. Then spent the next two hours screeding it off.
Consulting my old anatomy book, I've injured the Quadratus Lumborum on one side.
Really could do with cycling to the shops tonight - not sure I can manage it. Well, I might get there, not sure I'll get home. Vitamin I before I set off I guess.
[Edit] well I finally went on Fri eve. Lo and behold, back doesn't hurt when cycling!
So I can ride, but walking or sitting at a desk is really not comfortable.