I have chronic reumatism, and beeing both a professional piano player and a computer programmer, this has put a lot of strain on my hands. I've found that typing on a computer keyboard, makes my condition worse, however playing my Yamaha Upright Piano, helps my condition. A reumatologist explained that the computer keyboard strains my hands because they stay rigid in the sam position over a long period of time, but playing the piano is a dynamic excellent work-out that makes my muscles stronger. But playing light-action digital pianos in bars is stressfull again because the action is too light, so that my fingers smash against the keybed when the keys hit the bottom. This puts strain on my fingertips and nails. I don't know how this translates to keyboards, but I imagine that if you play like a pianoplayer it's good for your hands, but if you keep your hands stiff and rigid moving from chord to chord, it's not good.

But I believe that playing with proper technique will help you strengthen your muscles and ease the stress on your hands and wrists.

I recommend Chuck Levelles DVD, he goes through stretching and dynamic excersices that has helped me a lot!

Doc-Z