Well ..my less dominant arm is stronger than my dominant one...I do things with my dominant and tend to carry heavier things in my less dominant..therefore my least dominant arm is stronger..I do not have ALS my husband does..
I'd again try to train using a heavier weight in the weaker arm..if you feel after awhile you are losing more strength go back to your doc,,,in the meantime try to avoid reading too much about ALS..see if the doc can prescribe something better for the anxiety...medications too may cause an off- feeling and some weakness,,,but they are often worth the side effects...Lisa
PS..A book feeling heavier in one arm means very little..if you were telling me however that in one arm you couldn't lift a book at all or struggling very hard to do so..then I'd be more concerned that something more serious than anxiety was going on physically ...as this would be an example of "profound weakness"