What is good posture?  The body is supposed to function as follows—our bones hold us up and our muscles move us.  If you can find an alignment that allows your bones to stack one on top of the other to let them hold you up, you have found good posture. Instead most of us are misaligned in our bones and are using the body’s muscles and ligaments to hold us up. This happens for a number of reasons.
It is easier to be on four legs then two legs. If you were a four legged creature your spine would be horizontal to the ground, and it would sit on top of all four legs fairly evenly. When we come upright we have to balance our vertical spine in space. Add to this the arrival of a lumbar curve that four legged creatures don’t have. Our lumbar curve which allows for us to be upright and bear the weight of the spine and everything above it, is new in evolutionary terms.
The act of standing upright is a balancing act. The ideal of having good posture requires us to be like a tight rope walker; always trying to remain upright with bones stacked vertically one on top of the other. But as soon as the bones lose alignment we fall off the rope so to speak and are no longer balancing. We become static creatures held up by the backs of our knees or the front of our thighs, or by a collapse backwards into the lower back.
Good posture is about finding your way into the support of your bones. When your bones hold you up your muscles get to relax until they are called upon to move you. If your muscles are forever working to hold you up, your ability to move will be compromised.
This is the sad reality for most people. Look at the pictures above and try to figure out if your alignment resembles the skeleton on the left or the skeleton on the right?
***