Nan

If you want the strength angle anyway, the specific quality is scapular protraction — pushing the floor away and rounding between the shoulder blades. Plank plus, where you push the ground away at the top of a plank and hold a couple of seconds, builds exactly that and it transferred directly for me.

Design isn't a frivolous criterion here. The failure mode of every budgeting app is that you stop opening it, so an app you enjoy opening is doing the actual job. I take that argument seriously. I just wouldn't take it over cross-platform when there's a second person involved.

This is the most self-aware answer in the thread and it's the one I'm actually chewing on.

Half right — movement is the actual variable. But a sit-stand desk is the easiest way to build movement into a job that keeps you in one spot, so I would not throw it out.

Locked knees with the pelvis forward is the default everyone drifts into. A soft knee and a foot rail fixes most of it without any conscious effort.

You bought a real solution and then implemented it at about three times the dose anyone should start with. Standing is a load too, and four hours a day from a standing baseline of zero is a big jump. That band across the low back after 40 minutes is usually fatigue in the muscles holding you upright, plus the very common habit of pushing the pelvis forward and locking the knees. What worked for me:

• Start with 15 to 20 minute standing blocks, and sit down before you are uncomfortable rather than after.
• Total about 90 minutes a day for the first fortnight, then build.
• An anti-fatigue mat. On a hard floor this is not an accessory, and the difference is obvious within a day.
• Shift your weight and put one foot up on a low rail or a box, swapping every few minutes. Static standing is worse than static sitting in some ways.
  If it does not settle with those changes over a few weeks, get it looked at properly rather than buying more gear.

The within-session looseness is mostly nervous system rather than tissue, which is why it resets overnight, and that is completely normal for the first couple of months. Lasting change is slower: most people notice something that persists between sessions somewhere around 8 to 12 weeks of consistent work, and real structural change is measured in months. Two things speed it up in my experience: hold long enough to matter, 90 seconds to two minutes rather than 30 seconds, and add some strength work at the end of your range instead of only stretching, because the body keeps range it can control and gives away range it cannot.

Not a mistake, just an early check-in. Take a photo of your forward fold today and another in six weeks. The change is invisible day to day and obvious across that gap.

Also stop thinking of it as one correct position. The healthiest change I made was not sitting better, it was sitting in three or four different ways across a day and moving between them. Static perfect posture for six hours is still static.