muscle spasms

To preface, I'm brand new to the world of Aneros. I had my third session (using a Progasm) last night. Shortly after beginning I began having a series of full-body muscle spasms, small at first but quickly building in intensity and duration. Within minutes I was thrashing about uncontrollably. As soon as one ended, another began. It was just like I saw in the videos referenced elsewhere in this forum. I was able to achieve this in any position I tried. All told, the session lasted almost 4 hours (seriously). While the sensations were spectacular, I couldn't call them sexually satisfying. It was like being repeatedly and mildly electrically shocked, for lack of a better explanation.
My question is: how would this experience be classified? I doubt if I was experienceng dry orgasms due to the lack of sexual satisfaction, but what were they? And what suggestions does anyone have to help me reach the next level? Thanks!