Is Mac OS X's two finger scrolling damaging to your hand?
Out of all the Mac users I've ever heard of/seen, none of them have ever said anything like this. I swift touch of a trackpad of mouse certainly doesn't seem to be any sort of damaging movements. If you end up having problems with it more you could ask a more 'medical' associated person. I've personally never heard anything like it, but muscle pains can be worsened from certain movements causing stress. Good luck!