When I first started doing yoga, it was an unconscious thing - I started holding myself better, sitting taller, having good posture. It just felt
good to sit upright, be open and spacious. I didn't even realise it till one day my sister exclaimed her envy of my spine!
Now I see it in all yogis, and it is quite different to the way most of us Aussies love to slouch! We work & spend hours on computers, we do lots of driving, we shield our hearts (physically) - it's no wonder a hunched back is a usual site.