Capisco

woah this one super expensive. They've the ant-eater chair (Hag Capisco) that makes you move your body throughout the day. Have not got the chance to try it though.

The most flexible backrests I've used, in descending order: Haworth Zody, HON Ignition 2.0, Herman Miller Mirra (either version), and Steelcase Leap V2 (which is still very, very flexible). I've never had the opportunity to sit in a Fern, but I believe it also has a very flexible backrest. Below the

I've put a few in a Hag Capisco because it can be turned around for sternum support. Others remain preferential to the cheaper, more versatile Inkbed Inkstool.

I have a Hag Capisco. It's a perfect for the remote office worker that keeps a guitar by their workstation. It's (imo) quite pricey and not the most comfortable for the behind. I should add that it was gifted to me and doubt I would personally pay that much for a chair.

IKEA Markus chair is worth a look. Good backrest and headrest, and the price isn’t bad. HAG Capisco is another option, but it’s on the expensive side... You can also check out ergonomicchairfinder. lots of folks recommend it for finding ergonomic chairs that work for you.

I had a HAG Capisco at the office and had to change it. It has a too rigid posture for me. I'm the kind of guy who puts the leg under the bum, and I'm always moving, so that chair is very uncomfortable for me :/

At my last place we had these chairs. It was uncomfortable and not really a good fit for me. Many of my colleagues complained as well but the CEO just said that the chairs were not meant to be comfortable and you should move around a bit. https://www.dpj.se/ergonomiska-kontorsstolar/17370-235141-hag

HAG Capisco gave me quite some discomfort in an area where I really don't want to have discomfort, if you know what I mean. Felt like being on the saddle of a bike (not a comfortable bike) for the whole day.