I recently attended a wonderful family wedding in a fabulous ancient church that offered stone seats and backless benches throughout the ceremony and banquet. This made for some interesting posture watching as I observed how people coped without back support for so many hours.
Some coped beautifully. They were forced to sit on their seat bones. In this position slouching is more difficult and finding that correct position where balance is achieved by the shoulders being held above the pelvis and the head held directly above the shoulders becomes the easiest least stressful way to sit.
Others struggled. I call them the C sitters. They sit with the sacrum tucked under their bodies the back is rounded, many of the postural muscles that support the torso are turned off. Such bodies struggle to find balance and become exhausted trying to hold everything up.
Passive Hanging is so good for you. It lengthens the muscles attaching the arms to the body and spine. This gives better range and freedom of movement, elasticity to the shoulders and takes the strain off the poor lumbar spine that is often left to soak up the work that the shoulder girdle isn't managing. It also allows a little intervertebral stretch, it opens the space between the chest and pelvis allowing all your organs a sort of breathing space; literally, a chance to stretch out!
Active hanging means pulling yourself up with the arms kept rigidly straight. It activates and strengthens all of these same muscles and even corrects little uncomfortable vertebral twists.
You can take as much weight as you want on your feet until you are strong enough to dangle for 30secs with these little active pull ups.
To go back to my wedding. One particularly charming young man was having terrible trouble sitting at the table. When I checked him out he was unable to even initiate the muscle system required to hold up his chest. He couldn't locate the movement pattern in his neural network! But we got the system working again doing moves like those above and I am keen to find out how he is doing now.