lean over backward
To expend a lot of energy or effort to do something; to inconvenience oneself. I can't believe how ungrateful you're being, especially since we leaned over backward planning this dinner party for you! Please don't lean over backward preparing for my visit—I'm totally prepared to sleep on your floor!
bend/lean over backward, to
To exert oneself enormously, to go to a great deal of trouble to satisfy or please someone. Originating in the United States about 1920, this expression, with its image of straining to do a backbend, is well on its way to cliché status.
lean over backward
See bend over backward.