Has anyone ever pulled a muscle and didn't know how? I spent the afternoon at work listening to complaint after complaint from my boss, until, I started getting back into her face, and then, noticed this cramp on my chest side, tightened up like a vice, couldn't move. I guess instead of clenching my jaw like I will do, I did this. It only lasted a few minutes but, it was overwhelming, now my neck is stiff, lol. And, my back is sore. Anyone ever do this?