After trying a very large number of very expensive spaceship shaped chairs (Herman Miller, etc) I'm now pretty happy with IKEA's Alefjäll swivel chair:
https://www.ikea.com/gb/en/p/alefjaell-office-chair-glose-bl...
What this chair has going for it is that you can lower the backrest so that you can lean back over it. That takes a bit of weight off the lower back and leaves the shoulders free.
There are a lot of cheap, flimsy office chairs that can do the same, but they mostly don't have armrests and are generally too small.
The Alefjäll is very un-IKEA-like in that it has a very solid, even heavy, feel about it.