break a sweat

To put forth a large amount of energy or effort into or toward a task. (Likened to perspiring due to strenuous physical activity.) Usually used in negative constructions to indicate the opposite. That test was so easy, I aced it without even breaking a sweat. She didn't break a sweat becoming the district attorney. Those guys on the board are so intimidating! I don't know how you lead these board meetings without even breaking a sweat.

break ˈsweat

(British English) (American English break a ˈsweat) (informal) use a lot of physical effort: He hardly needed to break sweat to reach the final.