if you have fatigue from RD, then you'll always have fatigue from RD, you can't "get stronger" or immune to the horrible pain that is associated with the increased force required to activate almost all RD's in existence, head on over to the ergo forums, more ergo heads will answer, but in short, my opinion, no stretching/exercises is gonna help, just get a mech keyboard, now, RD's suck for fatigue (you don't HAVE to get an ergo mechanical, at least get a mech board tho).