I might be the only person here who disagrees in some way with this. I noticed that myself and other people I know only started developing RSI-type symptoms after computers got "fast enough". By that I mean that before that point there were frequent long-ish pauses when one couldn't do anything very much; at a certain point computers got so fast that such pauses became uncommon, and now it only really happens to me when I switch the machine on and wait for it boot and login.
The problem is that pauses are recovery time for your body. The good news is that once you've realised this, you can artificially introduce pauses into your routine, and give your body the chance to repair some of the damage caused by typing. I had big problems when I was a mere 21, and didn't use a computer for several months. With reading around, a bit of common sense, and a very gradual return to things, I not only got back to where I was, but now I use a computer and play guitar more than I did before. Getting better equipment is part of it (for me keyboard: http://maltron.com/ and a trackball: Logitech Trackman Wheel my preferred option), but the two most important things for me were: taking action as soon (i.e. on the day) I noticed problems; and taking breaks when doing things like typing. After a while you won't even notice the breaks are part of your routine.
The problem is that pauses are recovery time for your body. The good news is that once you've realised this, you can artificially introduce pauses into your routine, and give your body the chance to repair some of the damage caused by typing. I had big problems when I was a mere 21, and didn't use a computer for several months. With reading around, a bit of common sense, and a very gradual return to things, I not only got back to where I was, but now I use a computer and play guitar more than I did before. Getting better equipment is part of it (for me keyboard: http://maltron.com/ and a trackball: Logitech Trackman Wheel my preferred option), but the two most important things for me were: taking action as soon (i.e. on the day) I noticed problems; and taking breaks when doing things like typing. After a while you won't even notice the breaks are part of your routine.