I played (and posted) the piece too. Can also not imagine that playing it very often in a row is useful - cramps it what should be avoided ultimately, I think. Not only that it is no good for the technique, with cramps one never can play soft and lyrical. But force will not help, strength - I dunno. Maybe endurance?
Sorry if I wasn't clear - I wasn't trying to suggest force, as you seem to interpret it, as an approach
to playing the 25/1 in any way, only that force can best be achieved through coordination, and that of course it helps to have strength, and that the 25/1 and the 25/12 are good etudes for building strength. And yes, endurance is a good word, but the definition of endurance in this case is intrinsically linked to strength. I think that you guys are translating the word "strength" into some idea of forceful playing that I did not in any way mean to imply.
It seems to me that, you played a little too fast than your actual physical conditions.
That was precisely the point, though - the Etude, at that time, served as a judge of the strength in my fingers and forearms. I didn't practice enough to build the strength necessary to play it without fatigue. Which brings me back to the first post made in this thread. If you are used to playing on lightweight keys, it simply follows that you will have to build the strength in your fingers and arms back up again with a switch to weighted keys. Anything that employs a constant workout of your fingers/wrists/forearms will be beneficial, whether the exercise is delicate playing or ferocious playing. The various techniques that can be employed to avoid fatigue are pertinent, of course, but they don't negate the benefit of general strength-building exercises.