Someone asked me recently to just tell them the right way to sit. They wanted a shape, something they could picture and hold, shoulders back, chest up, spine stacked just so. I understand the appeal of a fixed answer. I do not think it exists, at least not in the way we have been sold it.
The popular idea of posture correction treats the body like a photograph that needs straightening. Pull the shoulders back, tuck the chin, lengthen the spine, hold it. In my experience this often creates a new kind of rigidity rather than a healthier one. I have watched clients grip so hard to maintain a corrected shape that they end up more tense, more braced, and paradoxically less able to move freely through the very posture they were told to hold.
Posture, as I have come to understand it through years of watching bodies rather than just measuring them, is less a shape and more a pattern of variability. A person who can comfortably slouch, then upright, then twist, then settle again, without pain and without effort, is in better shape than a person locked into one supposedly ideal position for eight hours because someone told them it was correct. The ability to change position easily may matter more than which position you are in.
There is also something posture reveals that has nothing to do with mechanics. I have noticed, and this is one view rather than a rule, that posture often shifts with a person's emotional state before it shifts with their training. Someone under pressure at work will often carry their shoulders differently than they did a month earlier, regardless of what exercises they have been doing. Treating that shift as purely structural, something to be corrected with a strap or a reminder to sit up, misses what is actually going on.
Better posture is not a position you achieve and hold. It is the range of positions your body can move through without bracing against itself. That reframes the goal from correction to capacity.
So when clients ask for the right way to sit, I usually ask a different question back. Can you sit like this, and then like that, and then back again, without effort. Can your body change its mind. If the answer is yes across a few different shapes, I am far less worried about which one a photograph would call correct.