back-breaking

изнурительная работа

Refers to any form of extremely demanding physical job or task.

Similar to 'work', but often implies manual, unskilled, and prolonged effort.

изнурительный труд

More literary or formal than 'work' or 'labour', emphasizing the wearisome and unpleasant nature of the hard work.

Относится к чрезвычайно тяжелой и физически требовательной работе.