A friend who has been going to exercise classes for health reasons was told by the instructor to imagine there was a string attached to her (my friends) head, which was pulling her up straight. This does seem like a good idea, and I think if you can stand up straight (my other half has difficulty with this,so it is not simple) then it does make you feel better I think. I am finding it hard to walk at a decent pace these days, which makes me really cross, pleases the other half, though because he can now keep up with me.