Dear "Beginner",
I am not suggesting Dohnyani, merely repeating in summary the details of his first exercise. Please, focus on "under supervision of a teacher" and what others have written: this is bit one serious way for more experienced players to carefully develop skill. But lke any powerful tool, used inappropriately is "potentially misguided and harmful". It seemed an example would give folks an idea of what the book was like before buying it, but your right to be concerned. It's a great question to raise. Maybe not for everyone?
That said, with supervision, it may be just the right medicine. I'm still learning, and marvel at concert pianists trills and seeming ease over difficult passages. But I ran into a problem with these; they're very intense, and fortunately I caught a side effect, as noted. Too much time on this, would cause my hands to feel "narrow", altering a free, wide range of arms like Chopin's "Military Polonaise" or Nocturnes. Czerny and Chopin balanced that.
I wasn't going to write this as it seemed too long, especially for the forum, but I met a woman who worked on her last 2 fingers ("3rd and 4th" or "4th & 5th": the pinkie and its neighbor.). We'd met in a music store and were talking about piano. She had so aspired to concert level, and as I asked, politely, what her scars were from on right forearm, was stunned to hear she'd had a nerve removed after it was "irreversibly damaged" by 3 hours a day of exercising the weak fingers. Not deterred, she recovered, and harmed a second nerve, incurring another surgery and eventually not being able to play.
I'm not a doctor, but I have been very athletic, learned typing on mechanic typewriters, and always kept ergonomic form, as taught for each situation and practice. I don't mean to scare anyone, I just share this as improper training for a person can not only lead to difficulties later (having to relearn fingering or fine motions), under the most extreme cases it can literally hurt you. I cried inside as the joy and gift of music can last a lifetime, amd should.
So I thank you for asking that poignant question, and graciously defer to the teachers out there, and maestros, for guiding aspiring performers in the best style possible.
Enjoy!
