I recently retired from SimplexGrinnell due to a rare neurological disease call Kennedy's Disease.  Its technical name is X-Linked Spinal Bulbar Muscular Atrophy.  Basically the nerves that control the voluntary mussels die and the mussels waste away over time.

In my case I have lost most my upper body strength, face and Jaw weakness and my legs get tired very quickly which hampers walking even short distances. 

For those of you that are interested you can get more information at http://www.kennedysdisease.org/.