I'd probably say, "Hey, I work out an hour a day, so sorry for the noise."
You pay rent to enjoy your space the way you see fit, and I doubt you're going to cause much more noise than your kiddos already do all day.
So I would talk to them, but I wouldn't make it an option to tell you no- it's your "home" and you choose to exercise in it.
Maybe they'll appreciate knowing what all the noise is about. They might assume you're having wild relations upstairs, but to find out you are only exercising might make them a little less anxious about it, lol!