Mousing should not injure you if done properly. Try using your shoulder rather than elbow. A short keyboard (no keypad) can help too.

Despite much attention to posture, mice and scroll wheels were a major cause of RSI for me.

After switching to the handshoe mouse, I have no mouse pain even if inattentive to posture. (I don't use the scroll wheel though)

It basically forces you to not use your wrist, and to use your shoulder.

If you get a 'vertical' mouse (either one that looks like it stands on its side or one that is like a sliding joystick), you basically have no choice but to use your whole arm - I've used one of those for a while, interesting experience.

Can you explain the biomechanics of what you mean? Not sure how elbows and shoulders relate to proper and improper mousing.

I was told myself that you should set your mouse sensitivity to the highest setting possible, so that you basically aren't moving the mouse, so there is no movement of your arm.

This is advice given to me during an ergonomic assessment.

Yes, but what was the advice?

0. Sit straight, arms to the side. Adjust desk and chair so elbows are in a 110 degrees angle.

1. Use a short keyboard (no keypad) so mouse and keyboard can be closer and arms can be facing forward.

2. Move mouse using shoulder rather than elbow.