Question: I've been having some tightness and tension in my wrists and forearms lately. I'm aware that you struggled through similar problems with discomfort. Do you have any exercises, stretches, or warmups you could recommend?
Albert's reply: First and foremost, if you have wrist and/or forearm tension that is causing you pain, you are doing something wrong. Pain is the body's alarm system, and your immediate response should be to stop and rest.
It is a near certainty that your technique is operating at suboptimal efficiency. While it is indeed possible to play the piano with excessive wrist and forearm tension, it only works up to a certain point, and even then usually not very well. Speed, dynamics and musical density (thick counterpoint and/or harmonies) will eventually join forces to defeat an inefficient mechanism. The inevitable response is to fight back with more of the same, trying to force one's way past the technical obstacles. This is a recipe for pain, and it does not make for beautiful playing.
Practice slowly—much slower than you consider slow—and softly. For several days at the very least, limit your playing to the softer half of the dynamic range. Challenge yourself to play truly pianissimo yet with full dynamic shaping. You will eventually return to normal playing with an expanded dynamic palette and a more beautiful sound as a result of greater ease.
It is essential to learn to distinguish positive muscle response to proper practice, similar to that of athletes after a good workout, from the pain that arises from sustained, improper tension. In either case, the body will give its own cues to stop practicing. A vital difference is the locus of any such feeling, which should only be in the fingers, never in the wrist or forearms. After an extended practice session, the fingers should feel alert, flexible and that they have done their work. You should feel nothing at all in the wrists or forearms.
Personally, my hands feel best after practicing detailed counterpoint such as fugues, since counterpoint requires such precise control of each finger in(ter)dependently of the others, holding one finger while releasing another, with each voice given its proper dynamic shaping and articulation. The hands will almost invariably feel fully worked after slow contrapuntal practice (or even slow practice of piano exercises); fast practice is not generally necessary and is often detrimental to good playing and technique.
I have only experienced problematic forearm and wrist tension once, and that was at the beginning of my piano studies. I was (improperly) practicing many Chopin Etudes at once, especially the first two, which are infamous for causing injury if improperly practiced. My technique was not sufficiently developed at the time, yet the biggest problem was my lack of good practice technique—my only speed at the time was prestissimo.
The ultimate solution is to slow down and rebuild your technique on a proper foundation, one free from the excess tension that is so counterproductive to beautiful piano playing. You will need to work one-on-one with an expert teacher who is able to train you from the ground up, who can teach you to control your fingers, wrists, forearms and elbows independently of one another. Barring that, I can recommend Alexander Technique, famous among musicians, actors and dancers, for learning to become aware of and eliminate unnecessary tension.