There has been many a times that I have come across a patient who would say to me that they know they have bad posture as if expecting me to reprimand them for it! They probably even got advice from us physios about keeping good posture!
There isn't a posture that is good if held for too long! Yes, a 'good posture' may be more visually appealing. For example, square shoulders and straightened back with tummy tucked in might be pleasing to the eye as opposed to one slouching. Try and hold either of these postures for long and you will feel discomfort/pain or fatigue. Any position in which a joint or joints are held in one position for a prolonged period of time causes discomfort and pain/fatigue. So instead of thinking in terms of having a good posture , one could think of rather not being in one posture/position for too long.
Postures in which joints are held in the extremes of their ranges tend to cause discomfort and pain quicker than postures wherein joints are not at the end of their range. So in this regard, some postures may be better than others (called optimal positions or ergonomics) but any posture held for too long is a recipe for pain and/ or discomfort!
Besides, our bodies were not designed to be in one position for hours except when sleeping! So the main key to avoiding some of our posture associated aches and pains is to just keep shifting positions frequently or just take a walk during breaks. As simple as this sounds it may not be easy to do so at one’s office when you busy concentrating on work. One therefore needs to be more body aware and if it means setting an alarm every 45 min to an hour to remember to just change position, so be it! Or whatever else works for you. Be creative in incorporating this in your unique work set-up. Your body will thank you for it! And, you might just say goodbye to posture related problems in the long run.