How strong do your arms need to be for pole dancing?

I am finding it really difficult although I have a fairly slim build - I have been to two cles and after the first cl my arms ached for four days and I could hardly move them and now every time I try to do the basic move (fireman spin) I find it difficult to lift myself and I have a pain the back of my left arm. Can anyone give me advice about how i can get better and why my arm is still aching??