Dear friend, having been injured(and recovered) myself, I have found that a lot of the standard wdvice given commonly such as "Play slow", even though partially correct, are inadequate. You need to become more aware of your body to avoid a few things, such as 'trapping' the motion of your hands Usually when we try to play fast and hard we 'lock' our muscles and tendons because we have the impression that increased -sense- of tension means increased power. It does not. Even this advice by itself is useless. I am really inviting you, if you have the patience, to check out this series of videos in youtube, which, in my opinion, is the best guide for ergonomy in piano-playing: http://www.youtube.com/watch?v=9zgoc...eature=related
It includes a series of exercises that you can try out and get a much more practical sense of when tension is building and why. If you understand the lessons (which you will, the teacher speaks too plainly even for my own taste :) ) you will start applying the principles to your playing. A final personal remark is don't push your muscles too hard: Same way as you can't lift 200Kg without excercise, don't expect to become a virtuoso without some -unbiased- excercise. I can't stretch this point enough. If you stress yourself you'll eventually get seriously injured.