I, too, have wondered why so "many" (four or five?) people on this forum who do not have ALS symptoms seem to think they have ALS anyway. Interestingly, they seem to be also involved in extreme exercising, body building, etc.
My hunches:
1) The statistics for actual ALS cases are correct.
2) Guys (and women) who are involved in body building and/or intense exercising are probably more body aware than the average couch potato, and so every dent or quiver in their silhouette looms large.
3) PERHAPS the urge to exercise excessively reflects some kind of body anxiety that is already there ... something like anorexia or bulimia in young women. Some need to achieve an idealized form and to have total control over one's body. (Don't want to get psycholanalytical on you, but there seems to be a "control" issue underlying the irrational fear of ALS. ALS is the ultimate "loss of control over one's body," and therefore seems to represent an irrational threat to some people, even those who do not have ALS symptoms.)
4) Perhaps excessive exercising leads to the kind of global twitching people report. Muscles were not designed by nature to be bulked up for no purpose other than bulking them up. This kind of twitching may simply represent over-stimulation of the muscles, combined with anxiety. (Remember I know nothing about this stuff, so take it for what it's worth.

)
5) Finally ... having a guy in Ohio, a guy in the UK, a guy in Canada, and a guy in the northwest (or where ever) meet up on an internet forum does not constitute a "cluster." What are the commonalities? You're exercise enthusiasts. You have twitches or other symptoms that are
not characteristic of ALS. Yet you are all convinced that you do have ALS.
My hunch is that there is some other anxiety that this ALS obsession is masking. But then, I live in La-La-Land, and we go for weird theories here. I'm sure Wright or Al or others will have the correct explanation.
You all sound like great guys ... smart, nice people. Hope you get some relief from your worries soon, i.e., find the correct solution to your symptoms and accept the answers you're given by professionals.
Good luck!