Just anecdotal, but there are many fit, marathon runners that have suffered from this, myself included. I had LC for five agonizing months. I think it was because I tried running through some of the mild symptoms that caused me to get this. I don't think I lost my overall fitness, but rather my muscles/cells, etc. lost its ability process oxygen properly. Once I got "better", my ability to run fast returned quickly, like within one or two months.
Again, anecdotal, but your story checks out in that fit people who have described LC symptoms are almost always distance runners or very overweight. I'm really curious if there's something there and if the correlation to body-type exists at the tails for some reason.
