You know, I just turned 29. My knees have had arthritis since I was 24 at least. I got a Nike + insert for my shoe that communicates with my ipod (and has a slammin workout mix to boot), and its Kara Goucher's endurance training. When I first started the workout, I was still a smoker, and I would slow walk for the jog portions and fast walk for the run portions. It alternates fast and slow which is the best for endurance training. I just pushed myself every time. I still use a puff of my inhaler before a workout, but now that my lungs are getting stronger, I find that I can fast jog (the most of a run I've ever done in my life) during the run portions and fast walk during the jog portion of the workout. I have it toned down, but according to my body, I'm amped up and feeling great about it. Of course, I am yet to lose weight, I am gaining muscle in my legs. I just do my "run" once a day, and I feel great. It also helps curb my dizzy spells that I'm getting from quitting my anti-depressants. I found out how bad they were on your body and have decided to go natural. The only pills I plan on taking from now on are birth control! You can do it!!!! You're already rockin it!