I have a rather weak lower back after a long period of inactivity/office work. It's not giving me any trouble yet but it soon may as I've just started a new job which entails a lot of lifting and carrying heavy loads. My upper body is fine, I have a decent workout a few times a week but I must admit that I've neglected my back and after a week or two in my new job I'm starting to feel the strain. What sort of lower back exercises could I try? I'm getting a lot of conflicting information from books and online.