Piano Forum

I was hopeful that s better pianist/teacher would answer your question. ...

No such luck with that, but I can offer just anecdotes.  I'm sure like many people here I played this sonata in younger years, and continue to use the basic technique of staggered octaves in either hand daily.

Triceps?  Really? 

That probably speaks to how indvidual a person's response to a movement might be.  I get hit with problems in the forearms when doing stuff like that for more than ten minutes at a time.

Clearly, the technique needs correction.  [ETA I guess I was thinking about the repeated notes/chords in rock/blues and so forth, which does still hurt me physically, although I do it very often, and not the tremolo or staggered octave walking bass.  So, my comments may not be strictly on-point, but the basic point remains that plenty of people, including me, can use fast octave tremolos in either hand, although probably not comfortably for several hours.]

Unfortunately, I've found for myself there's no real solution (except the obvious ones, about adjusting posture, which of course affects the geometry of the arms relative to the keyboard, and o forth), but I can offer the consolation that, no, it does not get easier with practice, and it's always going to be tiring. 

I think there's a good reason rock and roll players are often drenched in sweat, and not just because of the lights on stage or the heat of a room.

But the Beethoven first movement can be fixed such that you can make it through more than a few seconds at a time.