Drop-in Figure Drawing

Its been about 3 years since my last figure drawing class.  I decided to start going to "The New Art Center," in Newtonville,MA that has weekly open studio figure drawing. I felt so out of shape with the whole thing.  In the begining my hands had a shakiness and my shoulder was on fire after 40 minutes of constant drawing.  The model was excellent though, never moving. By the end of the session I felt everything start to come back again but I'm going to need to start going weekly to get myself back in shape.