Posture is not a position, but a dynamic pattern of reflexes, habits, and adaptive responses to anything that resists you being automobile upright and functional, such as:
Gravity, of information!
Awkward working conditions, which may be unavoidable (nurses must lift patients!), or self-inflicted and correctable (lousy ergonomics).
If you begin tip over, or lose the stability you need just for a task, postural reflexes kick in and engage muscles to get you into an additionally or less upright and/or functional position again. The biological systems and tricks that keep us upright are neat and surprisingly poorly understood.3
Posture is the embodiment of your comfort zone. At worst, it could be like a wire crate.
Posture is also more than the sum those parts, simply a collection of righting and stabilizing reflexes it's the way you live, the shape of your flexible container, the physical manifestation of your comfort zone. We habitually hold ourselves and move approaches that serve social and emotional needs, or avoid clashing with them: posture can be submissive or dominant, happy or sad, brave or fearful, apathetic or uptight. Problems and rewards attempting to change posture are not just musculoskeletal, and pleasurable personally profound methods. Patterns and behaviours that lead to trouble are usually valid.4 This article does not get too deep and mostly sticks to the musculoskeletal issues, but the potential profundity of posture deserves a nod..