Heavy lifting

A: You look pretty exhausted.

B: I am. Most of my teammates are either on holiday or sick. So, I feel like I’m doing a lot of the heavy lifting.

Note: Literally, this phrase refers to the act of picking up and carrying heavy objects. Metaphorically, it means “most of the work involved in something” or “the most difficult part of a task.” For example: Fathers went off to factories and left the heavy lifting of child-rearing to women.