back-breaking

腰の砕けるような仕事

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

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

骨の折れる苦役

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

非常に過酷で肉体的にきつい仕事を指します。