Is there any stage of IVF when hot yoga is safe?

So I have chronic back pain and hot yoga is the only thing that makes a real difference (I've tried basically everything but surgery, which is not in the cards). I haven't done it in 2 years, basically since we started trying, and my back has suffered. I'm on BCPs this month prepping for our first IVF (starting stims Sept 4), so I signed up for a month of hot yoga. OMG, y'all, it is so good for me in so many ways.

That said, I know it's not safe during stims or after transfer. I'll be doing freeze-alls with PGS - what about about after ER and before transfer? How long after ER is there still risk of torsion? Any chance of issues during FET prep?

Thanks!