The same thing happened to me when I learnt to invert V about 2 months ago. I tore a rhomboid muscle – after a couple of trips to the physio and dry needling and 5 acupuncture sessions, it seems to be nearly healed. I think my problem isn’t getting into invert V position – it’s after I’ve done it, I just let go of all the muscles and flop down so now I’ve started locking on to the pole and sliding down instead and so far my back is ok. I’m also making sure I warm up properly now. (having a pole at home, it is so tempting to just walk past my pole room and go in for a few inverts with no warm up at all – I was so excited to learn these moves after the basic beginner spins and climbs but now I now I need to warm up.