The Egyptians enslaved the Israelites with backbreaking, i.e., demoralizing and unusual labor.
When the Egyptians saw that conscripting the Jews to build storage cities did not succeed in checking their birthrate, they added mental demoralization to the hard work in order to break their spirits, correctly believing that this would weaken them physically, as well:
First, they made the men do women’s work and the women do men’s work. The change in routine was unusual and unsettling, and both the men and the women found themselves ill suited to each other’s jobs: the women were not strong enough to do the men’s work, and even though women’s work requires less raw strength than men’s work, the endurance it requires was more than the men were capable of.
Second, instead of having them build storage cities, they made them do work without purpose, simply for the sake of afflicting them. This was particularly demoralizing, for even if a person is forced to work hard, he can at least pride himself on having done the job well if there is a specific objective. But if there is no objective and the work has no end, it is both physically and mentally backbreaking.
This is the meaning of backbreaking, demoralizing and unusual labor.
—From the Kehot Chumash