I'd love to start some sort of exercise routine. I tried the elliptical......couldn't do that for more than 3 minutes without my legs becoming like jello. Same thing with the treadmill. About five minutes is all I can manage without my legs becoming very weak. So weak that I can't support myself. I'm wondering if an exercise bike might be the ticket. Something I can do while sitting down. I hate to invest more money into something that I can't use but I need to do something. It has to be something I can do at home since I don't drive and have no way to go anywhere. Any advice?