muscle spasm
"After experiencing a nasty bulge disc , L5/6 and diagnosed with retro lethesis I spent 3 years from chiro to physio , but couldn't kick the intense pain in my back which would go all over my back. At times I'd be in bed for days. 

I saw a pain specialist and was given norflex. I took 100mg once a day and after 2 days I was pain free.  I now only take it when it flares which isn't often.  It changed my life for the better."