[rewsiffer]

I am in a similar (age, mobility) situation and I got into indoor rock climbing about a year ago. Since then I have lost weight and gained a ton of muscle. I go around twice a week.

I always hated going to the gym because it was boring, but rock climbing is fun and challenging, like solving a puzzle. Also, I find I work a bit harder because it triggers your animal instincts of not wanting to fall. I do mostly top rope climbing(bouldering scares me). If you have a rock gym nearby, setup one or two trial sessions and see if you like it.