From Pitchfork interview:
http://www.pitchforkmedia.com/article/feature/42415-interview-wilco
Pitchfork: How are you feeling now?
Jeff Tweedy: I feel great! It's been three years since I went into the hospital. I've never felt better. I've never been healthier. I haven't had a cigarette in two years. I run four or five miles, four or five times a week. I've been healthy and having a really good time.
Pitchfork: You should run the marathon.
Jeff Tweedy: Well, I wouldn't be able to survive it. My knees are...I mean broke both my legs running too much last summer.
Pitchfork: You broke both your legs?
Jeff Tweedy: I had stress fractures in both my tibias from running too much. You know, once you're an addict, you're always an addict, so just because I found something good to do doesn't mean I'm not going to hurt myself doing it. So, I've had to cut back because of that. I didn't run last summer at all. I swam.