I'm getting bored with my daily 1 hour walk on a nearby paved multiple use recreational trail. I'd like to get a bike but haven't a clue what to get. I'm 55, 6', 185 lbs. with a large frame and have a really bad lower back (minimizing stress on my lower back and straightening up occasionally to stretch will be important). But sitting bolt upright on a single speed CCM with a basket up front, like the one the Wicked Witch of the West rode, sure doesn't appeal. I pass regular stress tests with my cardiologist and use a heart rate monitor - so I'm serious about fitness. What do I need to know in shopping for a bike? MTN bike, touring, road - what type of bike would be most appropriate? What size of wheel, type of tire, shape of seat, frame and handlebars, etc. Cost is an issue so the best bang for the buck is important. Any suggestions would be appreciated. Thanks.