Hi sjgcit,
Thanks for your response.
No, it's not the position. I actually have another baby grand which I've played on since I was a kid. When I set up my digital piano, I took all the measurements from that, including the bench height and key distance from the floor.
I've experimented with bench height in the past. The only thing I ever noticed is that if I sit too low, my thumbs will contact the keys further back (away from the tips) and they end up getting a little sore.
But this is nothing like the problems I've had with my hands since I started playing on digital pianos 6-7 years ago. It seems obvious to me now, but at the time, I couldn't figure out what was causing it. What problems did I have? Soreness on the tops of the hands, weakness in fingers (unable to 'stand' on a finger), tightness going back to the elbow, burning hands, a feeling like a need to stretch my forearms, a pulling feeling when I opened my hand wide (like someone was pulling strings to make my hand close). When it was really bad, I couldn't write or type on the computer.
I thought the problem was caused by something I was eating or some exercise I was doing. I didn't think it was the digital piano, because I didn't really notice much difference in touch -- certainly not such a difference that would cause physical problems. I had several different digital pianos - yamahas, casios, kawais, rolands. For a time I thought I was just getting older and couldn't play piano everyday anymore. So I would play twice a week or even once a week.
Last year, the piano at my school became unbearable. It kept falling out of tune, and I was tired of tuning it. So, I decided to take my VCP1 there. This meant that I no longer practiced on it at home. True, I played a little at school on the digital piano, but there it's very easy music. Just a starting pitch for the choir or a simple hymn -- nothing technical. Within a few months, my hand problems started to go away. Keep in mind, I was still playing on my baby grand at home. After 1/2 a year, my hands have basically recovered. I'd say 95%.
When I think back, it should have been obvious to me. After I would finish practicing on the digital piano, my hands would feel tired and sore, especially on the tops of the hands. It's too bad, really. I don't know what's the difference between the two pianos. Maybe someone can figure it out. It's something to do with the action. I know that my hands would feel really bad after drilling so called 'hammer' passages. One particular example comes to mind: Var 12 of Mendelssohn's Variations Serieuses. There, you have to work much harder on the digital piano. Something about how the key bounces back.