bend over backwards (to do something)(for someone)
Fig. to work very hard to accomplish something for someone; to go out of one's way (to do something) (for someone). He will bend over backwards to help you.I bent over backwards for you, and you showed no thanks!
Also, lean over backwards. Exert oneself to the fullest extent, as in Dad bent over backwards so as not to embarrass Stasia's new boyfriend. This phrase transfers the gymnastic feat of a backbend to taking a great deal of trouble for someone or something. [c. 1920] Also see under fall all over.