What does good posture look like when sitting and standing?

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Good posture looks comfortable and adaptable: your head balances over your body, your shoulders stay relaxed and your joints are not forced into position.

Can I judge my posture from a mirror selfie?

A mirror can show your position at that moment, but camera angle and how you pose affect the result. It cannot identify the cause of pain or tell you which exercises you need.

Should I keep my stomach pulled in while walking?

You do not need to hold your abdomen tightly throughout a walk. Let breathing remain easy and choose a pace you can manage. Follow individual instructions if a clinician has given you a specific exercise.

Does a rounded upper back mean I have failed at posture?

No. Spinal shape varies and can change for reasons beyond habit. A new curve, a rapid change or associated pain warrants professional assessment rather than repeated attempts to force yourself straighter.

Can someone else check my shoulders for me?

They can describe what they see, but uneven shoulder height alone is not a diagnosis. Ask them to observe rather than push or reposition you. Persistent symptoms are a better reason to seek an assessment.