Why is alberti bass so tiring?

Question

I am practicing the second movement of Mozart's K 545 sonata. I notice that Alberti Bass is very tiring. More so than other 16th note rhythms. So much so that I feel the burn in my left hand because the left hand is almost all Alberti bass. I also tend to slip from Alberti bass to arpeggio in the second movement when I slow down and practice hands together and I think it has to do partly with how Alberti bass is so tiring.

But why is it so tiring that I start feeling the burn when I'm not even halfway through the movement? I mean yes, I am playing legato except for where Mozart wrote dots above the notes in which case I play staccato(quite a few right hand passages end with a staccato note in an otherwise legato phrase) but does that legato have anything to do with Alberti bass being so tiring?

Here is what I am talking about:

It is only up to the first repeat but it shows you what I mean by legato ending in a staccato note and the left hand being mostly Alberti bass. This particular script has an implied legato in the left hand and is what I have both in my binder with the whole sonata and in Sonata Album Book I which has this sonata among others by Mozart, Haydn and Beethoven. But I have seen other scripts write an explicit legato for the left hand.

I'm not playing any faster than I should be. If the sixteenth note got the beat, this would be at Presto. Of course, it is the quarter note that gets the beat but this second movement, to me is at least as difficult if not more so than the first movement(which has a lot of 16th notes but at a more 50/50 ratio as to whether in a given passage, the 16th notes will be in the right or left hand).

Why is the Alberti bass so tiring that I can't even get halfway through the movement without feeling the burn? And how can I make it not so tiring for my left hand?

Answer 1

Unless you are playing this insanely fast (it is the slow movement of the sonata!) you should be able to play a bass line like that for hours on end with no strain or tiredness at all (though you might get bored...)

As the other answer implies, you need to stop trying to play everything "with your fingers" and start using the larger muscles in your arm to take the strain. This is a good piece to start learning about forearm rotation, which is a good way to reduce tension in more difficult albert bass figures, and in other situations as well. See these tutorials.

Answer 2

As commented by Jomiddnz, you should be able to reduce your fatigue and strain by adjusting your technique.

Instead of thinking of pushing the keys for each individual note, think of the whole chord and hold your hand so it covers the whole shape and roll the hand to arpeggiate the notes of the chord. It may be useful to play the middle note closer to the back of the keyboard -- even if it's a little snug to fit your finger between the black keys -- so that your fingers don't have to move so much.

You should start feeling the muscular exertion higher up in the arm, just below the elbow where the real finger muscles are.

Answer 3

Also check for tension in your shoulders. "Holding" the arms up reduces their movement, which then forces the movement to the fingers, increasing strain, tension and fatigue. The arms can only move properly (as described above) when the shoulders are completely relaxed. When your shoulders are completely relaxed, your arms will feel "weighty." Then "arm weight" makes sense.