When we are putting our arms up in the air, i want you to take a look at how i am doing it. If they are very controlled, i want you to do the same. If you keep your arms up above your heart then it is an AUTOMATIC ELEVATION of your HEART RATE.
What i often see in class, is where ppl are holding their arms a bit lower then i am; ppl relax and either they dont know, they dont know because they arent paying attention, or they plain dont want to put the extra effort into it. I see this alot in my merengues when i am doing the march. you need to watch this, or when i am doing the side merengue thing that i do in 1,2,3, or Levantando los manos.. Here is a video of beto perez the creator of zumba with a few others teaching a master class. Take note of their form, how their arms are strong and upright, controlled, not dropping.
Do this in class and i PROMISE, you will feel it in your shoulders. Do it consistantly and it will tone up your arms tremendously! It is the little tiny bit more effort you put into your workouts that make ALL of the difference!