Adam,
Sorry you have not had a reply to your question. I am sure you understand how challening MG is physically to many MG'ers.
Does being able to WALK a MILE count?????
I used to be quite athletic, speed walker, tennis, golfer (wanna be), cycling, sailing, hiking, dancing and swimming..................
MG hit me in 2000 and these wonderful activities became history slowly but surely, and by 2004 I was unable to ACTIVELY engage in any of these activities. Ocular had progressed to general MG. Two myasthenic crises followed.
Today, I enjoy the above-mentioned activites vicariously, usually as an observer at an event and mostly on television.
Recently, but not often - when I am really blessed and MG is in control, (and an understanding skipper), and I have easy access to boat ropes (also known as lines) to hang on to - I have been able to enjoy an occasional sail boat outing as a "guest". Oh how I miss being a crew member !!!! Sailing uses soooooo many muscles!!!
HOWEVER, I have been on cellcept for about six months now.
Previous and current meds include mestinon (always and probably forever), prednisone (still), imuran (which was disasterous to my pancreas - and which, of course, I no longer take).
The cellcept has been WORKING.
Slowly I have been able to start walking more than just a block at a time.
I am now able to walk a MILE at a time !!! Takes me about 30 - 35 minutes - and
I use a walking cane (due to poor balance (I walk like a drunk) -
and besides, it scares the dogs 
). I usually walk early in the morning, before the sun and heat arrive......
And you know what?
I am so HAPPY that I am able to do this! At one point I was confined to a power chair and was unable to drive a car for almost a year!!!!
Hey !!
Any chance for a modified version of your "sports event" ??? 
By the way, your story is amazing and encouraging !!
Good luck !!!!
p.s. I guess I don't qualify as an Endurance Athlete....That's O.K.
My family, friends, docs -and my cat- think I have endured quite a bit already (too much, actually) - in this Marathon called MG.
As have many other myasthenics........
