跑步 and 游泳
Could someone please explain to me why words like swimming and running get divided into two parts in sentences like "she goes swimming for 30 minutes every day"? Thanks! I know how to make the sentence correctly for the Duo exercise, but I don't know why it is done or the grammar behind it.
Instead of thinking of them simply as verbs, you can think of them as verb-object compounds. Indeed, the following article suggests that a distinction shouldn't be made between separable verbs and verb-object phrases:
I think perhaps the article overstates the matter somewhat, but it does give a helpful way to look at it, and it's fundamentally correct.
Note the point that some so-called separable verbs can be abbreviated to their first character. I believe another thing that can sometimes happen is that the two-character verbal compound is stated, and then the notion is repeated with just the first character, e.g. in "我跑步跑了三十分钟", as a sort of topic-comment structure, which is common in Chinese.
Of course, don't assume all two-character verbs are verb-object compounds. "慢跑", "jog", would be an example of one that isn't.