Some people may need to take medicines before they work hard or exercise.

VOA: special.2009.07.28

That really wasn't meant to be hard, but what's relevant about this exercise is not the fact that it's hard.

这应该并不难,与此相关的东西,事实上并不难

耶鲁公开课 - 博弈论课程节选

it was a small seminar-- I had groups of students proposing two novels actually for the end of the syllabus, and the exercise gets you to think very hard about what you think this period is all about.

是以小组研讨课的方式进行-,几组学生提出两本小说,作为教学大纲上最后一本读物，这样做的练习的目的是,让你去思考这个时期的意义。

耶鲁公开课 - 1945年后的美国小说课程节选

He decided to overcome his physical weaknesses through exercise and hard work.

VOA: special.2010.08.05

Well, as an exercise in game theory, that really wasn't very hard.

作为博弈论的一个练习,这个确实不难

耶鲁公开课 - 博弈论课程节选

But a sudden start to hard exercise can cause headaches.

VOA: special.2010.03.30