At one time or another, you've probably been told or thought you have bad posture.
Although you know that posture has something to do with straightness and you could point out somebody with very bad posture easily, you may not find it so easy to define what bad and good posture are so let us start on defining an ideal posture.
First, understand that ideal posture as I'm speaking about it here is only relevant in the context of your resting standing position, with no special attention being paid to any intentional muscular contractions.
From the side, ideal posture is easy to spot. It would involve a straight line being able to pass vertically down through your ear hole, the centre of your shoulder joint, the hip joint, the midline of the knee and the centre of the ankle ankle joint (for ease sake, we can take this as the centre of the outside bone of the ankle).
Less than ideal posture would involve any deviation from this.
Looking from the front, ideal posture would be more or less symmetrical. Any deviation from this would be less than ideal.
With regards to the idea of straightness, it's more informative to think in terms of the maximal vertical height that can be achieved with the lateral landmarks being stacked directly above one another than anything being straight. In ideal posture, the spine - in spite of us being told to sit up and stand up straight for the longest time - has a curvature, slightly in at the lower back and slightly out at the upper back. These curves provide superb shock absorption and structural support and a lack of them can cause major health difficulties and injury propensity.
So think of tall rather than straight.
On top of this ideal neutral resting posture looking nice and stopping the Posture Nazis persecuting you, it's worth noting that it will aid everything from circulation to breathing to movement - fundamental things for sport and life, I'm sure you'll agree.
Posture is a complex, multi-faceted topic so rather than bore you and myself to tears writing the postural equivalent of 'War and Peace', I will come back to you again shortly with the next part of this series on how posture becomes less than ideal.
Float Sting - Sports Injury Rehab and Performance, Harley Street, London W1