Zumba Fitness

In order to unlock this achievement you must progress 3 stages. This means you need to fill up the bar at the bottom 3 times by mimicking the instructor's moves. Here's a few things that make the achievement easier. I did all 4 of the stage progression achievements on the first Beginner 20 min class on Easy difficulty. I found these routines to be the easiest. I'm a horrible dancer and I still managed to get the achievement by the Cool Down. I should note for people that don't know that the "Cool Down" is always the last routine in the class. If you haven't got the achievement by then, you only have a limited time to get it done. Another method of getting this achievement is to do it in the singles routines. The bar at the bottom fills up MUCH faster during these and can be filled 3 times rather quickly. Only problem is that you have to be good at Zumba lol. If you consider yourself a good dancer, you can save yourself a lot of time by doing this in the single routines. Pick one you're comfortable with and try to stay in the green the whole routine and the achievement will be yours!

EDIT: You can't access the Stadium venue until you have completed the first 45-minute Zumba Party routine.

You can also do this on Zumbathon. I did it on Easy. It took a fair amount of effort but I was doing it for the exercise so it was a good driver.

The progression that you need to do is exactly as Beachem says above.