When you get told to stand up straight the first reaction is to adopt the “military” stance: chest out shoulders pinned back and shoulder blades contracted towards each other.
This will quickly feel unnatural and possibly painful. But there is more. This rigid stance can go as far as causing damage to the vessels and nerves that pass under the now contracted neck and pectoral muscles giving some people pain and numbness in the arm and fingers (a condition called Thoracic outlet syndrome). So how should we hold ourselves without going to these extremes, but at the same time avoiding a slouched stance?
In Pilates we often talk about a light engagement of the “corset muscle” (Transversus abdominis) that would hold your torso up and is light on the legs. The chest is open with wide collarbones. The shoulders are relaxed down but not braced. And finally there is space and width at the back between the shoulder blades (avoiding both winging and squeezing).
If this sounds easy then you are in a good place and you can hold a relaxed but supported upper body posture that will carry you well in your daily activities with minimal fatigue to neck, shoulders and back.
If however this seems like an impossible challenge chances are that some parts of your upper body are tighter and some are weaker, keeping you from achieving that optimally balanced way of holding yourself. All is not lost as regular Pilates sessions, through a range of strengthening and stretching exercises, can help you work your way to a balanced upper body posture.