I really agree...not so much on the arms, but on the legs. I kept thinking during Stacked Lower Body that I was not lifting heavy enough...but then the next day I was so sore!I am just getting to the new series today after being under the weather for the last week+. I don't even know where to begin there is sooooooooooooo much variety. I am in awe. I will be focusing on this series for while! I've tried some of the weight work and my arms are sore. wow. i didn't even lift heavy!