muscle spasm
"I've been prescribed Flexeril a few times when I've severely pulled a muscle. I use it as a muscle relaxant only; to lower the pain of a spasm and be able to stretch the muscle a bit to loosen it.  When I was in PT I took it after when my muscles were tight and aching. It worked great for those days I overdid it. It's definitely not a pill to take during the day unless you've become accustomed to it. I can attest to efficacy for short term use up to 2 weeks, but am doubtful about how well it would work long term."