Jam will be different because of the more challenging choreography and the far-less free-form nature of the format. That's what I like about it though! It's not like you'll be replacing Zumba with Jam, it's a new and different thing for them to try.
I'm certified in Zumba ( it was a pretty easy course) but I choose not to teach it because I like Jam much better. But it is a lot of fun esp. if you love Latin music. It's one gigantic line-dance party! If I recall my training correctly, they don't like a lot of verbal cueing and want instructors to keep things very easy as far as cueing in general, so be careful of high-impact options.
Try it and enjoy the change of pace!
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