I was reading the following passage from an article, and I was confused about why the word рука changes forms, if it's still the same construction. I understand the ломай is just the imperative of ломать but why would руки change to рук?
Руки ломать is literally "to break one's hands" -- a more vivid version
of the English "to wring one's hands." Both mean "to be terribly upset
about something." In English you might express the meaning rather than
the gesture. Не плачь, Аннушка, не ломай рук. (Don't cry, Annushka,
don't despair.)
Here's the full article -- it's really quite interesting:
http://community.livejournal.com/learn_ ... tml#cutid1