Everything. He would sit behind me and dictate keystrokes (mostly driving emacs, of course) to do email, edit code, and generally operate the computer. I don't want to talk about someone else's medical situation, but I think it's well-enough-known that rms had a period of RSI so severe that he was barred from using a keyboard to let his wrists/hands recover.

A few hours in a row of hearing and typing C-Space C-u 2 4 M-w C-x C-b <RET> C-y C-x C-s is exhausting. It was also amusing (in retrospect) to get a polite-enough admonishment to "don't think about what the keystrokes are doing; please just type what I say" when he could tell that I was slowing down because I was paying too much attention to what the intent behind the keystrokes was.