One way to reduce repetitive-strain injury from Emacs is to avoid pressing two keys simultaneously with the same hand. That is, avoid using modifier keys. For C-KEY, use one hand for KEY and the other for Ctrl. For M-KEY, do similarly as for C-KEY, or press and release Esc and then press KEY. And of course, take advantage of the automatic indenting and other features of Emacs that save keystrokes.