I like to answer questions on posture on the Quora platform where people ask the general public about anything and everything. This question appeared in my inbox the other day:
How can I have good posture? My back always hurts when I try to sit/stand straight.
It has to be one of the most common questions that Alexander Technique teachers hear, so this was my reply:
By recognising that posture isn't a position, but a movement, a balancing act. Replace the word posture with poise and you'll have a better relationship with what you're after. Poise is as much a mental attitude as a physical activity.
One of my pet hates with regards to articles on good posture is the obligatory accompanying photo with a plumb line drawn down the side connecting the ear, shoulder, hip, knees and ankle (so ignore the thumbnail image for this article!). It gives the impression that you’re supposed to achieve this position. You are not, that line is really just the average of all the points you have wobbled about. We can "wobble" with great skill and ease, the movement maybe be barely perceptible at times, but that subtle dance needs to be always available. It’s the attempt to achieve a held position that causes your back to hurt as it takes too much effort, and is ultimately unsustainable, as you’ll well know if you’ve ever tried to hold a “correct” posture.
It's also helpful to recognise that ultimately Isaac Newton was wrong about gravity (although it was a genius first step), it's not a force, and isn't dragging you down. We've known this since 1916 when Albert Einstein first published his Theory of General Relativity.
As counter intuitive as it may seem, the Earth is actually pushing us up, and we “surf" that upwards thrust by adjusting and readjusting to re-find the support it gives us through our skeletal structure. We're naturally an unstable structure (the trade off being we have greater mobility). Go on YouTube and look up “is gravity a force” and take your pick, lots of good short explanations on the reality of gravitation.
We use gravity like a fish uses water, we're completely evolved for it. It's not a matter of doing good posture, as it does you in a similar way that you don't need to think of breathing correctly, you will be breathed. The question is really what are the habits you've built up that interfere with your poise?
I'm naturally biased as a teacher of the Alexander Technique, but I recommend you look into it to help with your posture/poise.