Sorry to interject into this great conversation, but I don't know if this is done everywhere? I've been a pole student for a year now, and before my teachers even attempted to get us to invert, they made us get on acrobatic rings and (without jumping) told us to pull ourselves up using our core and shoulder muscles.
Once we got that, they then said to pull our feet over into a sort of pike… I learnt all my inverts that way, and (touchwood) haven't hurt myself or pulled any muslces.
(My teachers over here in Aus are awesome by the way if anyone wants to visit :D)