I have a backache. This isn’t an uncommon thing: I walk home from school, often carrying about 20-25 pounds in my bookbag (blame it on the calc text.)
But I’m wondering what, exactly, causes back pain (usually in my lower back). I know it’s not sore muscles, partly because I’ve been carrying this type of load every day of the school year since freshman year. I’m also a martial artist, have a low BMI, etc - I know it’s not that I don’t have the back strength to deal with it.
So what, exactly, causes a sore back? It’s not strenuous activity, and I do know that my bookbag isn’t off-balance or what have you.