I've been doing this workout 3 times a week, for the last 2 weeks. My arms are sore--a lot, but I've been pushing myself pretty hard. I do all 3 parts (after watching the first video, there should be a link to do part 3, and after that part 4.)
I've also been doing these:
Flat Tummy Workout--No crunches!
My arms and core are the areas I need the most work on. Zumba and running have helped me burn off a lot of fat, now it's time to tone and strengthen!