A backpack with a stiff back creates lots of problems such as back pain, strain on muscles, etc. If your North Face backpack is stiff then there are many reasons for this problem. 1. If you overstuff your North Face backpack. Your shoulders struggle to haul such a heavyweight and you suffer back and mussels pain at the end of the day. 2. Sometimes we forget to adjust the shoulder straps properly, which causes tight and narrow straps that hurt our shoulders.