I have read this question: “I like to do (be) something” vs “I like doing (being) something” and I get (although the answer could not be applied to my example) that using "to do" means in general I like to do it. While "doing", means I'm doing it at the moment or soon will be.
I found the following example in a grammar book:
Exercise means doing something with the body.
Shouldn't it be "Exercising means doing..." or "Exercise means to do..." or maybe "To exercise means doing ..."
-I don't get why exercise is used as a noun here.
-I don't get why doing is used instead of to do and if they are interchangeable (without context)