I started out doing just 40 minutes of cardio - elliptical, rowing, and treadmill - a few times a week. My cardio workouts now last an hour - 20 minutes of elliptical, 20 of rowing, 10 of the side-stepper, and 10 on a significantly inclined treadmill. I'm still not a fan of any of those, I have to admit. But about a month in, I also added the weight machine circuit, and that sort of workout I can say I have come to enjoy, and even look forward to.
You might not know this, but "circuit training" and "weights circuit" are terms that decades back meant something quite different. They're what, technically speaking, we call "equivocal" or "polysemic" - that is, they have multiple distinct meanings. When I first started training in high school, and then continued it passionately through my army, college, work, and into my grad school days, I used that earlier meaning. Then I got out of shape for years, and when I started exercising again, I did so on my own. Not part of the gym culture, I had no idea that the terms had changed their signification and reference. And so it was only recently that I learned what they now mean. I had an experience tonight that brought the old meaning back to mind for me.