I also have a friend who has one child. Running is her life. Literally. The doctors have told her that ONE of the reasons she is unable to keep a pregnancy is because she runs too much. She also goes to the gym for two hours a day (well, not on Sundays). My point? There are many, many good and not so good things (although when a piece of cheesecake hits your tongue, it's hard to think it's a bad thing) in the world, and they all need to be taken in moderation. We need to steer clear of the extreme.
I saw this a few years ago and still think it's funny. Careful, some may find it...graphic(?), so I'm apologizing now if I offend you, not my intention.
Why Exercise Frightens Me
What's gonna happen when they stop weight training...?