muscle spasm
"I had some very tight, non-spasming, muscles in my back.  Acute myo-fasciatis or something like that.  For some reason, my doctor prescribed Flexeril, Vicodin 5/500 and 800 mg Ibuprofen.  I didn't like the idea of taking Ibuprofen with acetaminophen, so I just used the Flexeril and Vicodin.  It worked very well, but I couldn't do anything but turn into a pile on the couch when taking both."