break (one's) back

To put forth a great deal of effort. I've been breaking my back trying to get a passing grade this semester, so failing by two measly points is incredibly frustrating. Don't break your back trying to please these people—they'll never appreciate it.

In tennis, to win a game immediately after losing the previous game as the server. The tennis star broke back seven times after losing serve during the tournament.

(to do something) Go to break one's neck (to do something).

Also, break one's neck. Make a great effort, work very hard. For example, I've been breaking my back over this problem for the past week, or Don't break your neck to get there; we'll wait for you. Both versions of this expression, polite equivalents of break one's ass, transfer the literal fracture of one's back or neck to figurative exertion. However, break one's neck has the secondary connotation of proceeding with reckless speed, a sense also conveyed by the term breakneck pace. Originally this idiom alluded to literally breaking one's neck by rushing heedlessly along, but it has been used figuratively for the past 300 years. Also see break the back of.

If you break your back to do something, you work extremely hard to try to do it. When you're breaking your back to make a business work, it's going to cut into your time with family. `I had been travelling all over the country, breaking my back just to get a job,' she says.