Thankfully my MG is very (*very*) mild. I've recently started physio therapy to rebuild muscle tone and stamina. Three weeks in and it has been fantastic for me. I think the important thing about exercise and MG is to listen to your body. Push the exercise "just enough" that it is doing you good and not exacerbating the MG.

My physio researched MG before we started and is being quite careful not to let me push it too hard, but is pushing enough that I'm getting better. If your health plan covers physio for conditioning purposes, I highly recommend it.

I agree with all posts above me though, when I'm down and the MG is hitting hard, there's little sympathy from those around me who don't really get it.