Many years ago, I saw a girl named Charlotte Reardon on an episode of Lifeline, a cable show that dealt with one topic per episode. That day, it was the CF program at, i think, DC Children's.
A few years later, out of the blue, I am looking up stuff on cross country running in NCAA Div. 3. The conference site I look at is actually hosted by University of Rochester (bleahhhh! I live in Pittsburgh, home to Carnegie Mellon). I find, by acident, that Reardon is actually on UR's x-country squad.
A few months later, I find that Cahill has done a webcast on her. She is doing amazingly well, it seems. I thought I heard she was able to run at least 10 miles a day, even in her redshirt season, which she took in Austria, I believe.
Although it may be hard for the average CFer to go to these extremes, it would seem like exercise would do the CF body lots of good. Just take whatever precautions necessary.
Give the soccer (or whatever else) a chance. If it works, good, if not, then maybe something else.
