I've almost always HAD a bike of some sort, save for a few stretches w/o, but I didn't really get "serious" about it until age 50. I had purchased a road bike and was just starting to get into it(was still mostly a gym rat), and then I had a hernia, and then the surgery to repair it. Cycling was one of the only things I felt comfortable doing w/the hernia, and also one of the first things I felt safe/good about doing post-surgery. I'm quite certain it really sped up my recovery. I then bought my first mountain bike at 52, and have since given up road altogether( I realized I hate riding in traffic). I now mountain bike 3-4 times a week on a rigid single speed 29r that I acquired late last year and am more hooked than ever. Will be 55 in a couple weeks. I plan to ride rigid ss mtbs until I simply can't move anymore!