I knew I had done something wrong when I heaved a heavy backpack strap over just one shoulder, instead of carefully scooting down and getting both straps positioned on my back, before standing upright. After two days I went to the doctor, as I couldn't exercise . My sleep wasn't affected, but I was worried I might have broken a rib. If I coughed or sneezed, the pain was an 11 on a 1-10 point scale. The doctor had me cough and had me move through a set of exercises. The diagnosis was easy. The remedy has been to rest my left arm (no exercise or heavy weight) and take Aleve for a week. After two days I feel fine, but will follow his orders to be sure. I'm going to be more careful with suitcases and heavy things in general since I am over 70.