Tried spinning

I gave spinning a try... it seriously kicked my ass. I went into this class think, "I have been running and taking zumba and riding my bike for months, this shouldn't be too bad." Wow I was not prepared for my legs felling like jell-o after only the first hill interval. Every time the instructor told me to "push it" I wanted to get off my bike and full body tackle that skinny bitch to the ground. The only thing that stopped me was being uncertain that my legs could support my own body weight. Ok... maybe I am exaggerating a bit. The instructor was actually very friendly and she told me at the beginning of class that she may tell me to do things in an attempt to push me further but I should ignore her if my body was telling me to rest. So I did. I didn't have a problem with sprints or jumps it was when she wanted us to stand for longer than a couple minutes that I had a problem. I didn't feel too bad after the class as far as sore legs (although my butt is sore from the bike seat). I will definitely try a spinning class again but what I really need is a different upper body workout. Does anybody have an upper body workout the enjoy and/or has shown results?