What fingers do have is a "memory"....I think loud playing helps our fingers remember what to do. I often do loud playing (and staccato sometimes, too) playing when practicing my repertoire pieces. Honestly, I don't do much technique outside my pieces....I do sometimes do scales....
I do scales and drills. When I'm done, I feel like my fingers are stronger. E.g., if you were working on a trill, and on day one, you played it for as long as you could. If you continued to practice that same trill, every other day for a week or two, I would guess you'd would be able to play it longer, faster and louder than you did at the start.
And to be sensinble, you wouldn't play the trill for as long as you could during the conditioning process. I wouldn't know what your exercise course would be, but I bet a teacher here could suggest a program.
(Now please don't read my questions here as being disputatious. I'm asking politley. Honest.)
But if you're "flexing" your fingers (so to speak. by slamming them into the keyboard), aren't you working the muscles in the forearms, thus developing those muscles? And when those muscles are strenthened, it's manifested in the finger speed and force of your finger action, right?
And, Maryruth, have you clicked on the link that shows the diagram of the muscles in the fingers. They're there - kinda puny, maybe, but better than nothing.
