Hi, I'm posting this on behalf of a friend who recently learned to ride a bike. He's got a hybrid bike and every time he goes out, he gets a really sore lower back. Doesn't seem to matter whether he's carrying a heavy load or not. I was just wondering if anyone else has experienced this or has any idea what might be going on. Maybe it's like any new exercise, you're just sore for a while afterwards? Any thoughts/comments appreciated.